Effectiveness of double checking to reduce medication administration errors: a systematic review

Abstract

Background:
Double checking medication administration in hospitals is often standard practice, particularly for high-risk drugs, yet its effectiveness in reducing medication administration errors (MAEs) and improving patient outcomes remains unclear. We conducted a systematic review of studies evaluating evidence of the effectiveness of double checking to reduce MAEs.

Methods:
Five databases (PubMed, Embase, CINAHL, Ovid@Journals, OpenGrey) were searched for studies evaluating the use and effectiveness of double checking on reducing medication administration errors in a hospital setting. Included studies were required to report any of three outcome measures: an effect estimate such as a risk ratio or risk difference representing the association between double checking and MAEs, or between double checking and patient harm; or a rate representing adherence to the hospital's double checking policy.

Results:
Thirteen studies were identified, including 10 studies using an observational study design, two randomised controlled trials and one randomised trial in a simulated setting. Studies included both paediatric and adult inpatient populations and varied considerably in quality. Among three good quality studies, only one showed a significant association between double checking and a reduction in MAEs, another showed no association, and the third study reported only adherence rates. No studies investigated changes in medication-related harm associated with double checking. Reported double checking adherence rates ranged from 52% to 97% of administrations. Only three studies reported if and how independent and primed double checking were differentiated.

Conclusion:
There is insufficient evidence that double versus single checking of medication administration is associated with lower rates of MAEs or reduced harm. Most comparative studies fail to define or investigate the level of adherence to independent double checking, further limiting conclusions regarding effectiveness in error prevention. Higher-quality studies are needed to determine if, and in what context (eg, drug type, setting), double checking produces sufficient benefits in patient safety to warrant the considerable resources required. CRD42018103436.

Full text

KoyamaAK, etal. BMJ Qual Saf 2020;29:595–603. doi:10.1136/bmjqs-2019-009552 595
SYSTEMATIC REVIEW
►Additional material is
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1Centre for Health Systems and
Safety Research, Australian
Institute of Health Innovation,
Faculty of Medicine and Health
Sciences, Macquarie University,
Macquarie Park, New South
Wales, Australia
2School of Nursing and
Midwifery, Centre for Quality
and Patient Safety Research,
Faculty of Health, Deakin
University, Geelong, Victoria,
Australia
3Alfred Health, Melbourne, VIC,
Australia
Correspondence to
Dr Alain K Koyama, Centre
for Health Systems and Safety
Research, Australian Institute of
Health Innovation, Macquarie
University, Macquarie Park,
NSW 2113, Australia;
alain. koyama@ mq. edu. au
Received 12 March 2019
Revised 23 July 2019
Accepted 24 July 2019
Published Online First
7August2019
To cite: KoyamaAK,
MaddoxC- SS, LiL, etal.
BMJ Qual Saf
2020;29:595–603.
►http:// dx. doi. org/ 10. 1136/
bmjqs- 2019- 009680
Effectiveness of double checking to
reduce medication administration
errors: a systematicreview
Alain K Koyama ,1 Claire- Sophie Sheridan Maddox,1 Ling Li,1
Tracey Bucknall,2,3 Johanna I Westbrook 1
© Author(s) (or their
employer(s)) 2020. Re- use
permitted under CC BY- NC. No
commercial re- use. See rights
and permissions. Published by
BMJ.
ABSTRACT
Background Double checking medication
administration in hospitals is often standard practice,
particularly for high- risk drugs, yet its effectiveness
in reducing medication administration errors (MAEs)
and improving patient outcomes remains unclear. We
conducted a systematic review of studies evaluating
evidence of the effectiveness of double checking to
reduce MAEs.
Methods Five databases (PubMed, Embase, CINAHL,
Ovid@Journals, OpenGrey) were searched for studies
evaluating the use and effectiveness of double checking
on reducing medication administration errors in a
hospital setting. Included studies were required to report
any of three outcome measures: an effect estimate
such as a risk ratio or risk difference representing the
association between double checking and MAEs, or
between double checking and patient harm; or a rate
representing adherence to the hospital’s double checking
policy.
Results Thirteen studies were identified, including
10 studies using an observational study design, two
randomised controlled trials and one randomised trial
in a simulated setting. Studies included both paediatric
and adult inpatient populations and varied considerably
in quality. Among three good quality studies, only
one showed a significant association between double
checking and a reduction in MAEs, another showed no
association, and the third study reported only adherence
rates. No studies investigated changes in medication-
related harm associated with double checking. Reported
double checking adherence rates ranged from 52% to
97% of administrations. Only three studies reported if
and how independent and primed double checking were
differentiated.
Conclusion There is insufficient evidence that double
versus single checking of medication administration is
associated with lower rates of MAEs or reduced harm.
Most comparative studies fail to define or investigate
the level of adherence to independent double checking,
further limiting conclusions regarding effectiveness
in error prevention. Higher- quality studies are needed
to determine if, and in what context (eg, drug type,
setting), double checking produces sufficient benefits
in patient safety to warrant the considerable resources
required.
PROSPERO REGISTRATION NUMBER
CRD42018103436.
INTRODUCTION
Medication safety continues to present a
serious challenge in hospitals. Processing
medications involves multiple steps
and individuals. Medication errors can
occur during different stages, with a
high frequency occurring during admin-
istration.1 2 Medication administration
errors (MAEs) are reported to occur in
20% to 25% of dose administrations.3 4
While prescribing and dispensing errors
can be intercepted as a medication order
proceeds towards patient administration,5
interventions to reduce errors during
administration are especially critical as it
is the final step before a patient receives a
drug.5 Various strategies have been devel-
oped and implemented in clinical practice
to minimise MAEs.
The process of double checking is
adopted as standard safety practice in
many hospitals, as well as in other high-
hazard industries such as aviation and
nuclear power.6
Double checking medication admin-
istration involves two individuals veri-
fying the same information, while single
checking involves a single individual veri-
fying the information.
The potential safety benefits of double
checking rely on two key factors: two
separate individuals verifying key infor-
mation and independent verification. Two
individuals should result in fewer errors
by minimising endogenous errors that
arise from one individual and are there-
fore independent from errors that may
arise in another individual.7 Exogenous
errors that arise from external factors,
such as illegible text, are potentially
reduced through independent double
checking when verification is performed
without one checker priming the other
with information to be verified.7–9 Several
studies have, however, demonstrated that

596 KoyamaAK, etal. BMJ Qual Saf 2020;29:595–603. doi:10.1136/bmjqs-2019-009552
Systematic review
organisational double checking policies often differ in
their level of detail of how the double- checking process
should be conducted, contributing to variation in the
application by nurses.10–12 Some organisations require
double checking for all medications while others only
for high- risk medications such as opioids, chemo-
therapeutic agents and intravenous drugs. Significant
resources are required, given the process requires two
individuals instead of one.
Evidence that the process is effective in reducing
errors is central to ensuring that this ingrained policy
is justified in terms of resource use and workflow
disruptions.13 14 Double checking has been imple-
mented in hospitals based on an assumption that it
will result in fewer MAEs, and at times as a response
to incidents when single checking was assessed to
have contributed to a serious error.15–19 However, its
effectiveness in reducing MAEs and improving patient
outcomes remains unclear. Much previous literature
on double checking involves qualitative studies. A
previous systematic review of studies published prior
to October 2010 investigated double checking during
medication dispensing and administration and found
only three quantitative studies which provided insuf-
ficient evidence to assess the effectiveness of double
checking in error reduction.20 Serious review of
this safety procedure is unable to proceed without a
sound evidence- base. Thus, we performed a system-
atic review to examine contemporary evidence of the
effectiveness of double checking to reduce medication
administration errors and associated harm to identify
both the strength of that evidence and where future
research needs to focus.
METHODS
Search strategy
Two reviewers (AKK and C- SSM) independently
performed each step of the literature search. A
Boolean search strategy (online supplementary eTables
1 and 2) was used to search for relevant articles in the
MEDLINE, Embase, Ovid@Journals and CINAHL
databases. Grey literature was searched using the Open-
Grey database (online supplementary eTable 3). Arti-
cles were searched from the inception of each database
through October 2018. Reference lists of all articles
included in the full- text review and review papers20 21
were also searched for relevant articles. Each reviewer
independently screened the title and abstract to first
identify relevant articles. Next, the full text of each
article was independently screened. After each stage,
agreement on included studies was reached through
discussion. This review followed PRISMA guidelines
for the reporting of systematic reviews.22
Inclusion criteria
For a study to be included, it had to evaluate the use
and/or effectiveness of the double checking of medi-
cation administration within a hospital setting and
report at least one of the following quantitative meas-
ures: (1) an effect estimate such as a risk ratio or risk
difference representing the association between double
checking (compared with single checking) and MAEs;
(2) an analogous effect estimate for the outcome of
patient harm. As the effectiveness of double checking
can depend in part on the extent to which nurses
adhere to the double checking policy, studies were
also included if they reported a rate of adherence to
double checking. Studies using either an observational
study design or randomised controlled trial (RCT)
design were included. Studies using an observational
study design are non- experimental studies that do not
randomise an intervention, which in this instance is
the double- checking process. The observational study
design categorisation is distinguished from the method
of ‘direct observation’ which is the use of observers to
collect information during a study. Studies involving
administrations of all medication types or select
groups of medications were included as were those
involving adult and/or paediatric populations. Only
English- language studies published in peer- reviewed
journals were included; abstracts and case studies were
excluded.
Data extraction and quality assessment
Data extraction was performed by two reviewers
(AKK and C- SSM) using a standardised extraction
form. Abstracted variables were used to characterise
studies and assess study quality. Variables included first
author name, year of publication, country of study,
years of data collection, study design, patient popu-
lation, sample size and types of medications studied.
If medication errors were assessed, the types of medi-
cations and errors, as well as the method of assessing
errors were recorded. Variables specific to the double-
checking process included the definition of double
checking used, how double checking was measured
(eg, through self- report or direct observation) and the
policy of double checking at the participating institu-
tions (ie, when double checking was required). Effect
estimates for the association between double checking
and MAEs or harm, along with corresponding p values
and/or CIs, as well as double checking adherence rates
were recorded. For one study,23 error- free medication
administration rates were transformed into error rates
for consistency with other studies. Study quality was
measured using the assessment tools provided by the
National Institutes of Health,24 assigning each study a
rating of ‘poor’, ‘fair’ or ‘good’. For RCTs, the Quality
Assessment of Controlled Intervention Studies was
used. For studies using an observational study design,
the Quality Assessment Tool for Observational Cohort
and Cross- Sectional Studies was used. The tools
measured study characteristics specific to the study
type (eg, adequate randomisation for trials) as well
as those common to both study types (eg, validity of
the methods used to measure the outcomes of MAEs

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Figure 1 Flow diagram for study selection.
and double checking). All studies rated as good quality
were required to have used direct observation to
measure both MAEs and double checking.
RESULTS
Study selection
The study selection process is illustrated in figure 1.
A total of 983 articles were retrieved from all data-
bases. After removal of 165 duplicate articles, 818
unique articles remained for the title and abstract
review. A further 789 articles were removed after
title and abstract review as they did not meet inclu-
sion criteria. From the resulting 29 articles, an addi-
tional three articles were added from hand searches of
references, resulting in 32 articles. Nineteen articles
were excluded during full- text review since they did
not report any measure of association between double
checking and MAEs, or double checking adherence
rate. Thirteen articles were included in the final review,
which comprised five articles reporting the associa-
tion between double checking and MAEs,16 23 25–27 six
articles reporting adherence rates28–33 and two arti-
cles reporting both measures.19 34 No studies assessed
patient harm as an outcome.
Study characteristics
The studies in the final review included 10 studies using
an observational study design,19 26–34 two RCTs16 23 and
one RCT conducted in a simulated setting.25 Studies
using an observational study design are described
in table 1 and RCTs in table 2. Seven studies were
conducted among adult patients,16 23 26 27 31 32 34 one
used a simulated adult patient25 and five involved
paediatric patients.19 28–30 33 The majority of studies
investigated all types of medications administered in
the hospital, while three investigated only specific
parenteral drugs.19 23 32 One study assessed only oral,
inhaled and topical preparations.16 Seven studies
investigated medication safety as a primary aim26 29–34
and double checking as a secondary aim.
Study quality varied, and many studies were under-
powered to provide meaningful results regarding the
association between double checking and MAEs. Three
studies had small study populations,25 29 33 and five
studies relied partially or completely on self- report to
measure medication errors, likely resulting in a large
under- ascertainment of actual error rates.16 19 23 27
Furthermore, one of these studies used self- report only
for double- checked administrations and medical
record review for single- checked administrations,
possibly biasing results towards a positive association
between double checking and a reduced medication
error rate.23 Two studies using an observational study
design reported very low error rates (1.2% overall26;
four errors in a 7- month double checking period
compared with five in a 7- month single checking
period27), making it difficult to adequately assess any
association between double checking and medication
errors.
Among studies using an observational study design,
the majority measured double checking through
direct observation26 28 30–34 and two used self- report
of double checking.19 29 One study did not measure
double checking but employed a before- and- after

598 KoyamaAK, etal. BMJ Qual Saf 2020;29:595–603. doi:10.1136/bmjqs-2019-009552
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Table 1 Studies using an observational study design investigating double checking of medication administration
Study Country
Sample size/
study duration Setting
Method of
measuring
double checking
Method of
measuring
errors Findings
Study
quality
Jarman
2002*27
Australia 14 months Inpatient units, operating suites,
birthing suite and ED at a
400- bed academic tertiary care
hospital
None (before and
after study of
change in policy)
Incident
report forms
►4 administration errors were
measured from March through
September 2000 (when
double checking was required)
compared with 5 errors from
March through September
2001 (when single checking
became standard)
Poor
Manias 200531 Australia 175 administrations
to 47 patients over
2 months
Metropolitan academic teaching
hospital
Direct observation – ►Adherence rate was 97% for
double checking of preparation
and 80% for double checking
to the patient’s bedside
Fair
Conroy 200730 UK 752 administrations
to 253 patients
over 6 weeks
Medical and surgical wards, PICU,
NICU, ED in a 92- bed paediatric
hospital
Direct observation Direct
observation
►In 84% of patients, nurses
were observed to double check
administrations
►Cursory double checks were
done on oral drug volumes and
intravenous infusions in 3% of
patients
►Independent checks of
calculations were not obvious
in 2% of patients
►Student nurses were allowed to
administer unsupervised in 1%
of patients
Fair
Alsulami
201428
UK 2000
administrations to
876 patients over 4
months
Medical and surgical wards, PICU,
NICU in a paediatric hospital
Direct observation Direct
observation
►Among 15 steps of
independent double checking,
adherence rates were equal or
greater than 90% for 11 steps
►For the four other steps,
adherence rates were 83%
for the actual administration,
71% for rate of intravenous
bolus, 67% for labelling of flush
syringes and 30% for dose
calculation
Good
Bulbul 201429 Turkey 98 nurses Paediatric emergency, paediatric
and neonatology, paediatric
surgery wards in two teaching
and research hospitals
Self- report Self- report ►64% of nurses reported double
checking while preparing or
administering high- risk drugs
Poor
Schilp 201432 Netherlands 2154
administrations of
intravenous drugs
over 1 year
ICU, internal medicine, general
surgery and other departments
administering intravenous
drugs in 19 hospitals (2
academic, 6 tertiary teaching,
11 general)
Direct observation – ►Adherence to double checking
was 52% for administrations of
intravenous drugs
Fair
Härkänen
201534
Finland 1058
administrations to
122 patients over 2
months
Medical and surgical wards in an
800- bed academic hospital
Direct observation Direct
observation,
medical
records
►In multivariate regression,
double checking was
significantly associated with a
lower odds of any medication
error (OR 0.44 (0.27 to 0.72))
►Adherence to double checking
was 81%
Good
Young 201533 USA 60 administrations
to 47 paediatric
and 10 adult
patients over 24
days
198- bed paediatric inpatient
hospital
Direct observation Direct
observation
►Adherence to double checking
was 75% (9 out of 12) among
continuous intravenous
administrations
Poor
Cochran
201626
USA 6497
administrations to
1374 patients
12 rural hospitals Direct observation Direct
observation,
medical
records
►16 of 29 (55%) preparation
and administration errors
occurred from administrations
done with a single check, 9
(31%) with a double check
and 4 (14%) with bar- code
administration
Poor
Continued

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Study Country
Sample size/
study duration Setting
Method of
measuring
double checking
Method of
measuring
errors Findings
Study
quality
Subramanyam
201619
USA 1473 intravenous
infusions over
1 year
Paediatric patients undergoing
radiological imaging at a tertiary
academic paediatric hospital
Self- report Self- report ►Intercepted errors decreased
from 4 per month to 1 per
month
►Adherence to double checking
was reported to be over 90%
Poor
*This study used a before- and- after design. All other studies were observational cohort studies.
ED, emergency department; NICU, neonatal intensive care unit; PICU, paediatric intensive care unit.
Table 1 Continued
Table 2 Randomised controlled trials investigating double checking of medication administration
Study Country
Sample size/study
duration Setting
Method of
measuring errors Findings Study quality
Kruse
199216 Australia 129 234 oral,
inhaled or topical
administrations over
46 weeks
3 wards of a geriatric
assessment and
rehabilitation unit
Chart review data
supplemented by
incident reports
►The error rate per 1000 administrations
was lower for double- checked
administrations (2.12 (1.69 to 2.55))
compared with single checking (2.98
(2.45 to 3.51))
Fair
Modic
201623 USA 5238 administrations
of subcutaneous
insulin to 266
patients
Patients with diabetes
at a 1400- bed
quaternary care
hospital
In double check group,
anonymous self- report;
in single check group,
review of electronic
medical records
►The error rate for double- checked
administrations was significantly lower
(28.8%) compared with single checking
(36.7%; p<0.001)
►In multivariate regression, double-
checked administrations were
significantly associated with a lower
odds of any type of error (OR 1.38 (1.23
to 1.55)), but not after adjustment
for nurse, to account for correlated
administrations (OR 1.18 (0.83 to 1.68))
Fair
Douglass
201825 USA 43 pairs of ED and
ICU nurses
Simulated adult
patient in a medical
education centre
Direct observation ►9% of nurses detected the weight- based
dosage error in the single check group
compared with 33% in the double check
group (OR 5.0 (0.90 to 27.74))
►54% of nurses detected the wrong phial
error in the single check group compared
with 100% in the double check group
(OR 19.9 (1.0 to 408.5))
►Adherence to double checking was
observed to be 100% (21 out of 21
nurses)
Good
ED, emergency department; ICU, intensive care unit.
design, assessing MAEs in the hospital before and after
implementation of a double checking policy.27 Among
the three RCTs, one study used direct observation to
measure adherence to double checking,25 while the
other two did not measure adherence.16 23
The majority of studies provided few details on
what steps comprised the double- checking proce-
dure. Only two studies reported the individual steps
in the medication administration process which
required double checking.23 28 In addition, only
three studies25 30 34 reported if and how independent
and primed double checking were differentiated.
Most hospitals required double checking based on
nurse qualifications and administration of high- risk
drugs,16 25 27 30 31 with one study requiring double
checking for all drugs.28
Double checking and MAEs
Three RCTs (table 2) evaluated the possible effect of
double checked compared with single- checked admin-
istrations on MAEs as the primary objective.16 23 25 Two
of these studies were conducted in a hospital,16 23 while
the third was a simulation trial.25 Although results
from two of the three studies reported a significant
association between double checking and a reduc-
tion in medication errors, methodological concerns
in each study limited the validity of the findings. In
a fair- quality RCT16 published in 1992, three wards
of a geriatric assessment and rehabilitation unit were
randomised in a cross- over design to have non-
restricted drugs either (1) double checked then single
checked, (2) single checked then double checked, or
(3) always double checked, as a control. A total of

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129 234 oral, inhaled or topical administrations were
evaluated over 46 weeks. MAEs were recorded from
chart review and incident reports, depending on the
type of error. The rate of errors was significantly lower
for double- checked compared with single- checked
administrations (2.12 (1.69 to 2.55) vs 2.98 (2.45 to
3.51) per 1000 administrations). Findings may have
been affected by an observer effect from study partic-
ipation, as error rates significantly decreased in all
wards over the course of the study. Moreover, results
were not adjusted for correlated administrations and
some types of errors were likely under- ascertained as
they relied solely on voluntary incident reports.
In a parallel RCT conducted at a quaternary care
hospital, 5238 subcutaneous insulin injections were
administered to 266 adult patients with diabetes across
two groups23: one group required double checking and
a second group was subject to standard hospital policy
that did not require double checking. Five medical
and surgical units were randomised to one of the two
groups. In multivariate regression, double checking
was significantly associated with a lower odds of any
type of error (OR 0.72 (0.64 to 0.81)), but this associa-
tion was no longer significant after adjusting for nurse
to account for multiple administrations by the same
nurse (OR 0.85 (0.59 to 1.21)). However, there was a
significant methodological flaw in the study. To record
MAEs, anonymous self- reporting was used for double
checking versus chart review for single checking. Study
quality was rated as fair, as under- ascertainment of
errors through self- report likely biased the results in
favour of the double checking group.
In a good- quality experimental trial involving care
of a simulated adult patient, 43 pairs of nurses were
randomised to a setting in which they would admin-
ister either a drug requiring a double check according
to hospital policy (insulin) or a single check drug
(midazolam).25 A wrong drug and wrong dose error
were both introduced as part of the experimental inter-
vention and nurses were directly observed to see if the
errors were intercepted. In the single check group, 9%
of nurses detected the dose error compared with 33%
in the double check group (OR 5.0 (0.90 to 27.74)).
For the wrong drug error, 54% of nurses in the single
check group detected the error, compared with 100%
in the double check group (OR 19.9 (1.0 to 408.5)). A
limitation of this study is the use of different drugs in
each scenario, as it is possible that nurses may be more
likely to double check insulin compared with midaz-
olam regardless of hospital policy.
Four studies using an observational study design
provided results for the association between double
checking and medication errors. In a good- quality
study of 122 medical and surgical inpatients at an
academic hospital, double checking was directly
observed to occur in 81% (856/1058) of administra-
tions.34 Details about medication administrations were
recorded by two independent nurse observers using
a structured form, and medication errors were iden-
tified by comparing information on the forms with
medication information in patients’ electronic records.
Multivariate regression showed that double checking
was significantly associated with a lower odds of any
medication error (OR 0.44 (0.27 to 0.72)). A further
study, in a large academic hospital, reported medica-
tion error rates before and after the introduction of a
double checking policy.27 Little could be inferred from
this study as the number of errors reported, based on
incident reports, was very low.
One study conducted in 12 rural hospitals reported
only the numbers of directly observed combined
preparation and administration errors that occurred
and reached patients, when different processes were
in place. Nine out of 10 errors reached patients when
double checks were used, 16 out of 23 during single
checks and four out of 12 during bar code adminis-
tration.26 In one study of the introduction of enforced
double checking for paediatric patients undergoing
radiological imaging, reported rates of intercepted
MAEs decreased from 4 to 1 per month, but study
conclusions were limited due to the small number
of MAEs.19 Six studies using an observational study
design provided adherence rates but did not test for an
association between double checking and MAEs.28–33
Adherence to double checking
Reported adherence rates varied from 52% to 97% of
administrations in studies of adult patients.31 32 34 Among
studies of paediatric patients, methods of reporting
adherence varied and ranged from 64% of nurses,29
84% of patients,30 and 75% to 90% of administra-
tions.19 33 One study of 2000 directly observed admin-
istrations in a small paediatric hospital reported adher-
ence rates for individual steps of the administration
process. Adherence was 90% or greater for 11 of
15 steps, and lowest for the actual administration to
the patient (83%), rate of intravenous bolus (71%),
labelling of flush syringes (67%) and dose calculation
(30%).28 The RCT conducted in a simulated setting
study found all 21 nurses in the double check group
used a double check as instructed.25
DISCUSSION
There is little compelling evidence from studies
undertaken in hospitals that double checking of
medications is associated with a significant reduc-
tion in MAEs. Only three good- quality studies were
found, among which two reported on the association
between double checking and MAEs.25 34 Of these,
one reported that double checking was significantly
associated with lower rates of MAEs compared with
single checking34 while the other reported no signif-
icant association.25 Of particular concern was the
use of self- reports or incident report data to measure
MAEs in 5 of 13 studies reviewed, given such measures
have been demonstrated to significantly underestimate

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the true error rate.35 While we did not identify any
studies with quantifiable evidence regarding the asso-
ciation between double checking and patient harm,
we can hypothesise as to the potential effects. Since
the proportion of MAEs that result in actual harm is
reported to be approximately 1% to 4%,34 36 even a
large risk ratio in favour of double checking conveying
a protective effect may not result in a substantial
reduction in harm. An important consideration in
assessing the value of the double- checking process is
its potential value in preventing rare but catastrophic
errors. Evidence of such occurrences is difficult to
identify as cases are most likely to rely on reported
‘near- miss’ incidents or case reports, which were not
included in this review. Large, robust trials measuring
both the frequency and severity of errors identified
and prevented during the double- checking process,
as well as potential and actual outcomes of errors are
required to more adequately address the question of
the effectiveness of the double- checking process.
A lack of evidence was also apparent in relation to
the fidelity of the double- checking processes applied
in the reviewed studies. Details of how compliance
was measured was rarely reported. For example, a key
component of the double- checking process is the inde-
pendence of the check, yet few studies reported on
this measure. Thus, the question arises as to whether
the lack of association between double checking and
outcomes is due to poor fidelity of the intervention
(ie, double checking is rarely performed in a rigorous,
complete way) or due to a lack of effect. Qualitative
studies have highlighted factors which may influence
the fidelity and effectiveness of double checking,
such as the automatic nature of the task which may
decrease one’s attention, diffusion of responsibility
between checkers, and deference to authority when a
junior nurse may not correct an error made by a more
senior nurse.13 14 Examples of the latter were directly
observed in one of the reviewed studies conducted in a
simulated setting.25 Future studies require closer atten-
tion to the details of the double- checking process used,
in particular the extent to which checks are performed
independently and whether all steps in the process are
completed as specified.
Defining and implementing double checking
There is considerable variation and often a lack
of clarity about how the double check should be
performed.13 14 37 38 Evidence from qualitative studies
and cognitive theory suggest a clear and consistent
process of independent double checking is desir-
able,9 13 but few studies report details of what the
double- checking process actually entails. Three of the
reviewed studies listed the specific items to be double
checked23 28 32 but provided no further detail on how to
perform the double check. One study provided a flow
diagram of the administration process that included
which items were to be double checked.19 Other
studies of double checking have reported the process
of double checking to range from no well- defined
procedure14 to standardised checklists8 or a flow chart
designed by a human factors team.39 While certain
aspects of a checklist, such as step- by- step instructions,
compared with abstract general reminders, have been
shown to be more effective in detecting errors,8 other
evidence remains scant as to which methods of double
checking may be most effective.
In addition, most studies investigating double
checking did not explicitly differentiate between inde-
pendent and primed double checking. Two studies
specifically described the double checking performed
as independent28 34 and one provided counts for
both independent and primed double checks.25
However, neither of these studies provided rates of
MAEs comparing independent versus primed double
checking. Independent double checking is preferred
since if the checker is primed, an error may not be
detected due to confirmation bias.8 Supporting this
point, in the simulation study, both the dosage and
wrong drug errors were discovered more frequently
during independent double checks than during primed
double checks.25 It is possible that double checking is
never truly independent in real- world settings regard-
less of how the double- checking process is defined.
For example, since the checker knows whose work
they are checking, confidence in the correct medica-
tion administration can become biased based on the
other nurse’s experience and qualifications. Moreover,
psychological theory suggests that any level of priming
between the two checks can substantially decrease the
probability of the checker detecting an error.40
Even if the double- checking process is well defined,
nurses may not be clear about how to put it into
action.11 38 Only two studies provided detail on how
double checking was implemented. One study, aiming
to reduce intravenous infusion errors in a paedi-
atric hospital, used multiple methods including staff
education, visual aids, reminders and a modification
to the electronic medical record system to properly
record double checking.19 Another study in a paedi-
atric hospital aimed to reduce MAEs through multiple
safety practices, including double checking, by training
nurses in a simulated clinical environment.41 While
there is a small number of examples, a well- defined
process of double checking and a structured, formal
method of training, along with feedback should be
employed for effective policy implementation. Despite
an absence of well- defined or reported definitions of
double checking, reported adherence rates were rela-
tively high across studies, ranging from 52% to 97%.
This may be partly a reflection of nurses’ belief that
the process is effective and of value to perform.
Limitations
This review includes potential limitations. First, non–
English- language studies were not searched, which

602 KoyamaAK, etal. BMJ Qual Saf 2020;29:595–603. doi:10.1136/bmjqs-2019-009552
Systematic review
may lead to publication bias. As only three of the 14
reviewed studies were rated as good quality, methodo-
logical limitations can also affect the collective findings.
For example, five studies partially or completely relied
on self- report to measure MAEs. Self- report likely
resulted in under- ascertainment of MAEs, limiting the
studies’ findings. Decreased power may arise if under
ascertainment was equal across all administrations,
or bias, if under- ascertainment was systematically
different across double- checked and single- checked
administrations.23 Many studies also had insufficient
sample sizes resulting in inadequate power to evaluate
the association between double checking and medica-
tion errors. In addition, many studies only conducted
basic bivariate analysis which may not properly account
for potential confounding and other biases. Reviewed
studies were also heterogeneous in their statistical
analyses and reporting methods, making quantitative
comparisons such as a meta- analysis infeasible. Lastly,
inter- reviewer reliability was not formally estimated
since consensus between two reviewers was reached.
Conversely, a particular strength of this review is that
it provides much updated evidence on the effective-
ness of double checking, reviewing an additional 12
quantitative studies published since a prior systematic
review.20
Conclusions
Double checking presents at face value as a logical
safety precaution which has been embedded in nursing
practice for decades. However, as this review reveals,
there is no solid evidence- base to support its use. Our
review of the evidence shows both an absence of good-
quality studies, and generally an absence of effective-
ness in reducing medication error rates and patient
harm. In most studies, the double- checking process
tested was ill- defined and the fidelity of the double-
checking process left un- investigated. Given the extent
to which it is embedded as part of routine nursing prac-
tice, and the considerable costs involved, there would
appear to be a compelling reason to establish a sound
evidence- base for its ongoing use and to inform deci-
sions about when and how it might be most effective
to improve medication safety. Higher- quality studies
addressing the limitations of previous studies are
needed including the measurement of robust outcome
measures that do not rely on self- reports of medica-
tion error rates. Current evidence is insufficient to
make recommendations about how, if or when double
checking should be performed in hospitals in order to
best improve safety. Even if double checking is indeed
an ineffective means of improving patient safety, it can
be very difficult to de- implement such a policy with
likely resistance to changes11 42 as well as potential
legal ramifications if serious errors subsequently occur.
Many hospitals are increasing the use of information
technology to facilitate the medication administration
process, and the ability for two nurses to sign off as part
of the double- checking process has become an essential
requirement in these systems. As such, their use may
further increase the time taken for the double- checking
process, as both nurses need to log onto the system,
rather than co- signing a paper chart. The introduction
of bar- coding may negate the need for two individuals
to check some steps of the process, but as several studies
have identified, workarounds and inconsistency in the
way bar- coding technology is used in practice often jeop-
ardises its effectiveness.43 Implementation of significant
work flow changes, associated with the introduction of
new technologies, however can be a useful impetus to
examine work practices and provide an opportunity to
re- consider long- held practices, informed by evidence.
Thus, even with the introduction of potentially helpful
technology, there remains a need for high- quality
research to address fundamental questions about when
and where double checking, either using humans or
technology, is beneficial to patient safety outcomes.
Contributors AKK was responsible for the study design,
literature search, data extraction, study quality assessment
and manuscript preparation. C- SSM was responsible for the
literature search, data extraction and study quality assessment.
LL and JIW contributed to the study design and manuscript
preparation. TB contributed to manuscript preparation.
Funding The authors have not declared a specific grant for this
research from any funding agency in the public, commercial or
not- for- profit sectors.
Competing interests None declared.
Patient and public involvement statement Not required.
Provenance and peer review Not commissioned; externally
peer reviewed.
Data availability statement All data relevant to the study are
included in the article or uploaded as online supplementary
information.
Open access This is an open access article distributed in
accordance with the Creative Commons Attribution Non
Commercial (CC BY- NC 4.0) license, which permits others
to distribute, remix, adapt, build upon this work non-
commercially, and license their derivative works on different
terms, provided the original work is properly cited, appropriate
credit is given, any changes made indicated, and the use is non-
commercial. See: http:// creativecommons. org/ licenses/ by- nc/ 4.
0/.
ORCID iDs
Alain K Koyama http:// orcid. org/ 0000- 0002- 1246- 2937
Johanna I Westbrook http:// orcid. org/ 0000- 0003- 1083- 8192
REFERENCES
1 Ruano M, Villamañán E, Pérez E, et al. New technologies
as a strategy to decrease medication errors: how do they
affect adults and children differently? World J Pediatr
2016;12:28–34.
2 Miller MR, Robinson KA, Lubomski LH, et al. Medication
errors in paediatric care: a systematic review of epidemiology
and an evaluation of evidence supporting reduction strategy
recommendations. Qual Saf Health Care 2007;16:116–26.
3 Westbrook JI, Woods A, Rob MI, et al. Association of
interruptions with an increased risk and severity of medication
administration errors. Arch Intern Med 2010;170:683–90.
4 Hayes C, Jackson D, Davidson PM, et al. Medication errors
in hospitals: a literature review of disruptions to nursing

603
KoyamaAK, etal. BMJ Qual Saf 2020;29:595–603. doi:10.1136/bmjqs-2019-009552
Systematic review
practice during medication administration. J Clin Nurs
2015;24:3063–76.
5 Noguchi C, Sakuma M, Ohta Y, et al. Prevention of medication
errors in hospitalized patients: the Japan Adverse Drug Events
Study. Drug Saf 2016;39:1129–37.
6 Spath PL. Error reduction in health care: a systems approach to
improving patient safety. Wiley, 2011.
7 Seki J, Turner L. Medication safety alerts. Can J Hosp Pharm
2003;56:97–9.
8 White RE, Trbovich PL, Easty AC, et al. Checking it twice:
an evaluation of checklists for detecting medication errors
at the bedside using a chemotherapy model. BMJ Qual Saf
2010;19:562–7.
9 Winters BD, Gurses AP, Lehmann H, et al. Clinical review:
Checklists—translating evidence into practice. Crit Care
2009;13.
10 Fossum M, Hughes L, Manias E, et al. Comparison of
medication policies to guide nursing practice across
seven Victorian health services. Aust Health Review
2016;40:526–32.
11 Schwappach DLB, Pfeiffer Y, Taxis K. Medication double-
checking procedures in clinical practice: a cross- sectional
survey of oncology nurses’ experiences. BMJ Open
2016;6:e011394.
12 Conroy S, Davar Z, Jones S. Use of checking systems in
medicines administration with children and young people.
Nurs Child Young People 2012;24:20–4.
13 Armitage G. Double checking medicines: defence against error
or contributory factor? J Eval Clin Pract 2008;14:513–9.
14 Dickinson A, McCall E, Twomey B, et al. Paediatric nurses’
understanding of the process and procedure of double-
checking medications. J Clin Nurs 2010;19:728–35.
15 Dobish R, Shultz J, Neilson S, et al. Worksheets with
embedded checklists support IV chemotherapy safer practice. J
Oncol Pharm Pract 2016;22:142–50.
16 Kruse H, Johnson A, O'Connell D, et al. Administering non-
restricted medications in hospital: the implications and cost of
using two nurses. Aust Clin Rev 1992;12:77–83.
17 Monroe PS, Heck WD, Lavsa SM. Changes to medication- use
processes after overdose of U-500 regular insulin. Am J Health
Syst Pharm 2012;69:2089–93.
18 Henry TR, Azuma L, Shaban HM. Learning and process
improvement after a sentinel event. Hosp Pharm
1999;34:839–44.
19 Subramanyam R, Mahmoud M, Buck D, et al.
Infusion medication error reduction by two- person
verification: a quality improvement initiative. Pediatrics
2016;138:e20154413.
20 Alsulami Z, Conroy S, Choonara I. Double checking the
administration of medicines: what is the evidence? A
systematic review. Arch Dis Child 2012;97:833–7.
21 Kellett P, Gottwald M. Double- checking high- risk medications
in acute settings: a safer process. Nurs Manage 2015;21:16–22.
22 Moher D, Liberati A, Tetzlaff J, et al. Preferred reporting
items for systematic reviews and meta- analyses: the PRISMA
statement. PLoS Med 2009;6:e1000097.
23 Modic MB, Albert NM, Sun Z, et al. Does an insulin
procedure improve patient safety? JONA 2016;46:154–60.
24 National Heart Lung and Blood Institute. Study quality
assessment tools [Accessed Nov 2018].
25 Douglass AM, Elder J, Watson R, et al. A randomized
controlled trial on the effect of a double check on the detection
of medication errors. Ann Emerg Med 2018;71:74–82.
26 Cochran GL, Barrett RS, Horn SD. Comparison of medication
safety systems in critical access hospitals: combined analysis of
two studies. Am J Health Syst Pharm 2016;73:1167–73.
27 Jarman H, Jacobs E, Zielinski V. Medication study supports
registered nurses’ competence for single checking. Int J Nurs
Pract 2002;8:330–5.
28 Alsulami Z, Choonara I, Conroy S. Paediatric nurses’
adherence to the double- checking process during medication
administration in a children's hospital: an observational study. J
Adv Nurs 2014;70:1404–13.
29 Bulbul A, Kunt A, Selalmaz M, et al. Assessment of knowledge
of pediatric nurses related with drug administration and
preparation. Turk Arch Ped 2015;49:333–9.
30 Conroy S, Appleby K, Bostock D, et al. Medication errors in a
children's hospital. Paediatr Perinat Drug Ther 2007;8:18–25.
31 Manias E, Aitken R, Dunning T. How graduate nurses use
protocols to manage patients’ medications. J Clin Nurs
2005;14:935–44.
32 Schilp J, Boot S, de Blok C, et al. Protocol compliance of
administering parenteral medication in Dutch hospitals: an
evaluation and cost estimation of the implementation. BMJ
Open 2014;4:e005232.
33 Young K, Cochran K. Ensuring safe medication administration
through direct observation. Quality in Primary Care
2015;23:167–73.
34 Härkänen M, Ahonen J, Kervinen M, et al. The factors
associated with medication errors in adult medical
and surgical inpatients: a direct observation approach
with medication record reviews. Scand J Caring Sci
2015;29:297–306.
35 Westbrook JI, Li L, Lehnbom EC, et al. What are incident
reports telling us? A comparative study at two Australian
hospitals of medication errors identified at audit, detected by
staff and reported to an incident system. Int J Qual Health
Care 2015;27:1–9.
36 Gates PJ, Meyerson SA, Baysari MT, et al. Preventable adverse
drug events among inpatients: a systematic review. Pediatrics
2018;142:e20180805.
37 Gill F, Corkish V, Robertson J, et al. An exploration
of pediatric nurses’ compliance with a medication
checking and administration protocol. J Spec Pediatr Nurs
2012;17:136–46.
38 Hewitt T, Chreim S, Forster A. Double checking: a second
look. J Eval Clin Pract 2016;22:267–74.
39 Evley R, Russell J, Mathew D, et al. Confirming the drugs
administered during anaesthesia: a feasibility study in
the pilot National Health Service sites, UK. Br J Anaesth
2010;105:289–96.
40 Swain AD. Handbook of human reliability analysis with
emphasis on nuclear power plant applications: final report, ed.
Sandia National Laboratories. Vol. 80. 662. Albuquereque,
New Mexico and Livermore, California, USA: The
Commission, 1983.
41 Hebbar KB, Colman N, Williams L, et al. A quality initiative:
a system- wide reduction in serious medication events through
targeted simulation training. Simul Healthc 2018;13:324–30.
42 O'Connell B, Crawford S, Tull A, et al. Nurses' attitudes to
single checking medications: before and after its use. Int J Nurs
Pract 2007;13:377–82.
43 Westbrook JI, Baysari M. Technological approaches for
medication administration. In: Tully MP, Franklin BD, eds.
Safety in medication use. London, UK: Taylor and Francis,
2016: 229–37.