A systematic review of the pain scales in adults: Which to use?

Abstract

Objective:
The study analysed the Visual Analogue Scale (VAS), the Verbal Rating Scale (VRS) and the Numerical Rating Scale (NRS) to determine: 1. Were the compliance and usability different among scales? 2. Were any of the scales superior over the other(s) for clinical use?

Methods:
A systematic review of currently published studies was performed following standard guidelines. Online database searches were performed for clinical trials published before November 2017, on the comparison of the pain scores in adults and preferences of the specific patient groups. A literature search via electronic databases was carried out for the last fifteen years on English Language papers. The search terms initially included pain rating scales, pain measurement, pain intensity, VAS, VRS, and NRS. Papers were examined for methodological soundness before being included. Data were independently extracted by two blinded reviewers. Studies were also assessed for bias using the Cochrane criteria.

Results:
The initial data search yielded 872 potentially relevant studies; of these, 853 were excluded for some reason. The main reason for exclusion (33.7%) was that irrelevance to comparison of pain scales and scores, followed by pediatric studies (32.1%). Finally, 19 underwent full-text review, and were analysed for the study purposes. Studies were of moderate (n=12, 63%) to low (n=7, 37%) quality.

Conclusions:
All three scales are valid, reliable and appropriate for use in clinical practice, although the VAS is more difficulties than the others. For general purposes the NRS has good sensitivity and generates data that can be analysed for audit purposes.

Full text

A systematic review of the pain scores in adults: Which to use?
Abstract
Objective: The study analyzed the Visual Analogue Scale (VAS), the Verbal Rating Scale
(VRS) and the Numerical Rating Scale (NRS) to determine: 1. Were the compliance and
usability different among scales? 2. Were any of the scales superior over the other(s) for
clinical use?
Methods: A systematic review of currently published studies was performed following
standard guidelines. Online database searches were performed for clinical trials published
before November 2017, on the comparison of the pain scores in adults and preferences of the
specific patient groups. A literature search via electronic databases was carried out for the last
fifteen years on English Language papers. The search terms initially included pain rating
scales, pain measurement, pain intensity, VAS, VRS, and NRS. Papers were examined for
methodological soundness before being included. Data were independently extracted by two
blinded reviewers. Studies were also assessed for bias using the Cochrane criteria.
Results: The initial data search yielded 872 potentially relevant studies; of these, 853 were
excluded for some reason. The main reason for exclusion (33.7%) was that irrelevance to
comparison of pain scales and scores, followed by pediatric studies (32.1%). Finally,19
underwent full-text review, and were analyzed for the study purposes. Studies were of
moderate (n=12, 63%) to low (n=7, 37%) quality.
Conclusions: All three scales are valid, reliable and appropriate for use in clinical practice,
although the VAS is more difficulties than the others. For general purposes the NRS has good
sensitivity and generates data that can be analysed for audit purposes.
Key words: acute pain, pain score, pain scale, pain intensity, pain management, emergency
department

A systematic review of the pain scores: Which to use?
I. Pain in the emergency department
Acute pain is one of the most common chief complaints reported by most patients
admitted to the ED, while its perception and expression have great variations between
countries (1). The definition of pain by International Association for the Study of Pain (IASP)
as 'an unpleasant sensory and emotional experience associated with actual or potential tissue
damage, or described in terms of such damage' is accepted worldwide (2).
Subjective and multidimensional nature of the pain experience render pain assessment
really challenging. In the Joint Commission on Accreditation of Healthcare Organizations
(JCAHO) guidelines, implementation of this standard in clinical practice comprised the
addition of pain as the "fifth" vital sign to be noted in the context of initial assessment; the use
of pain intensity ratings; and posting of a statement on pain management in all patient care
areas. Supplemented with regular pain reassessments, the schedule of pain reassessment
should be driven by patients’ pain severity (3).
Pain estimations need to be elicited and recorded to highlight both the presence of pain
and the efficacy of pain treatment. The patients’ perception of pain should be documented
during the initial assessment of a patient. Current evidence provides a general
recommendation that pain needs to be evaluated and managed within 20–25 minutes of initial
healthcare provider assessment in the ED (4). Pain treatment should be targeted to a goal of
reducing the pain score (eg, by 50%, below 4/10, or referred to as mild/ moderate or severe)
rather than a specificanalgesic dose (5).
II. Pain scores and documentation of pain
The patient’s self-report is the most accurate and reliable evidence of the existence of
pain and its intensity, and this holds true for patients of all ages, regardless of communication
or cognitive deficits (6).
In the absence of objective measures, the clinician must depend on the patient to
supply key information on the localization, quality and severity of the pain. Although
physicians commonly question the reported severity and rely on their own estimates, the value
of the patients’ description of the location and nature of the discomfort has been proved on the
theorethical basis and routine practice (7).

Pain scores have gained acceptance as the most accurate and reliable measure of
assessing a patient’s pain and response to pain treatment (5). Scales devised to estimate and/or
express the patient’s pain can be evaluated in two groups: Unidimensional and
multidimensional measures. It should be noted that unidimensional scales measure only
intensity, they cannot be viewed as a comprehensive pain assessment. Comprehensive pain
assessment is expected to encompass both the unidimensional measurement of pain intensity
and the multidimensional evaluation of the pain perception. The unidimensional pain intensity
scales commonly used bedside are:
Numeric Rating Scale (NRS),
Visual Analog Scale (VAS),
Verbal Rating / Descriptor Scale (VRS/VDS).
II.B.1. The VAS is the most widely used tool forestimating both severity of pain and to judge
the extent of pain relief (8). Healthcare worker asks the patient to select a point on a line
drawn between two ends to express how intense he/she perceives pain (Fig. 1). The VAS is a
continuous scale comprised of a horizontal (HVAS) or vertical (VVAS) line, usually 100 mm
long, anchored by two verbal descriptors (i.e.,“no pain” and “worst imaginable pain” (9, 10).
Patients are asked to rate “current” pain intensity or pain intensity “in the last 24 hours”.
The VAS is an easy-to-use instrument which does not warrant using a sophisticated
device. It is also highly sensitive indetecting treatment effects, and its results can be analysed
by parametric tests (11). Minimal translation difficulties have led to an unknown number of
cross-cultural adaptations (10). Although this tool is suitable for use with older children and
adults, the need for a marking and for being able to visualize and mark the line, can make the
VAS impractical to use in the emergency situation. On the other hand, most experts believe
that the VAS offers little practical advantage over verbal reports in the clinical practice (5).
II.B.2. The numeric rating scale (NRS) is a single 11-point numeric scale broadly
validated across myriad patient types. Data obtained via NRS are easily documented,
intuitively interpretable, and meet regulatory requirements for pain assessment and
documentation (12). To date, findings demonstrated that even in the chaotic prehospital phase
most acute care patients allow evaluation via a simple “zero-to-10 scale” or NRS reliably,
respecting their pain levels (13). Like the pain VAS, minimal language translation difficulties
support the use of the NRS across cultures and languages (14).

Evidence indicated that patients really want to give a pain number, rather than simply
relate whether they want analgesia. Strengths of this measure over the pain VAS are the ability
to be administered both verbally (therefore by telephone) and in writing, as well as its
simplicity of scoring. However, similar to the pain VAS, the pain NRS evaluates only 1
component of the pain experience, pain intensity, and therefore does not capture the
complexity and idiosyncratic nature of the pain experience or improvements due to symptom
fluctuations (10).
NRS is a commonly used tool necessitating the patient rate his pain on a scale from 0 to
10, with 0 indicating no pain and 10 reflecting the worst possible pain (Fig. 2). NRS are often
conducted as a scale from 1 to 10 which does not give the patient a solution to indicate no
pain at all. It can be used with children who are able to understand numbers. The pain scores
are interpreted as:
0 = no pain
1-3 = mild pain
4-6 = moderate pain
7-10 = severe pain
NRS can be used with most children older than 8 years of age, and behavioral
observation scales are required for those unable to provide a self-report (15). For patients with
cancer-related pain, the NRS is the most frequently used instrument to measure pain intensity
(16). Goulet et al. examined the agreement and correlation of electronic medical record-based
ratings of NRS and self-administered NRS in 1643 adult patients (17). The correlation was
high, but the mean electronic medical record-based NRS score was significantly lower than
the survey score (1.72 vs. 2.79; P <0.0001).
II.B.3. Verbal Pain Scores (VPSs), Verbal Rating Scales (VRS) or Verbal Descriptor
Scales: These tools may discern those patients who are truly in pain but who may not express
their discomfort, as well as influence the physician to inquire about the patient’s pain.
VRS consist of a number of statements describing increasing pain intensities (Fig. 1).
Patients are told to choose the word which best describes their pain intensity. The number of
descriptors used has ranged from four (none, mild, moderate, severe) to 15 (18). For patients
who have limited literacy or cognitive impairment, use of these scales may be difficult, and
they do not provide the number of choices available with the VAS or NRS, thus potentially
limiting precision (19).

This article reviews the current literature to provide systematic data regarding the
results from comparative studies on unidimensional assessment of pain intensity using the
NRS, VRS, or VAS. The following points were investigated to determine evidence-based
recommendations:
-Were the compliance and usability different among scales?
-Were any of the scales superior over the other(s) for clinical use?
III. Methods
A systematic review of currently published studies was performed following standard
guidelines. Online database searches were performed for randomized controlled trials
published before November 2017, on the comparison of the pain scores in adultsand
preferences of the specific patient groups. A literature search via the Cochrane Central
Register of Controlled Trials, PubMed/ Medline, ClinicalKey, EMBASE, the Cumulative
Index to Nursing and Allied Health Literature (CINAHL), and BIOSIS was carried out for the
last fifteen years on English Language papers. Published studies evaluating the patients’
preferences and usability ofthe pain intensity scales were targeted. The reference lists of
retrieved articles were used to generate more papers and search terms. Data were
independently extracted by two blinded reviewers. The discrepancies, on the other hand, were
resolved by the primary author. The research protocol to answer these questions was
registered in PROSPERO, the International Prospective Register of Systematic Reviews
(registration number is: CRD42017080974).
III.A. Search methodology
A comprehensive literature search was carried out using the following strategy:
Online searches were performed using the following search keywords and terms: (‘pain
assessment’ OR ‘pain intensity’ OR ‘pain score’ OR ‘pain comparison’ OR ‘pain scale’ OR
‘acute pain’ OR ‘pain rating’) AND (‘emergency’ AND ‘acute’ AND ‘score’). The search was
limited to human studies (clinical trials) conducted on adults and published in English.
III.B. Study selection, data screening and critical appraisal
The study included all comparative trials conducted to assess the use of commonly
used scales measuring acute pain intensity and to compare them with each other on specific
patient groups, exclusively in adults. All RCTs of any duration that investigated pain scores in
comparison to each other were identified. All potentially eligible papers were critically
appraised, with the emphasis on evidence from randomised trials and international guidelines
rather than smaller studies, case series and case reports. Reference lists of relevant systematic

reviews and all included studies were checked to identify additional eligible articles.
Conference abstracts and proceedings were not deemed eligible for inclusion in the review.
Citation titles and abstracts were independently screened and assessed regarding the
methodological quality by two reviewers (H.T. and O.D.). Any disagreements between the
two reviewers were then resolved by consensus or in consultation with a third reviewer (O.K.)
if needed.
III.C. Quality assessment and risk of bias
Eligible clinical studies were rated regarding the quality of evidence as per GRADE
guidelines and assigned to one of four groups: High (A), moderate (B), low (C) and very low
(D) quality (20).
Studies that met the inclusion criteria for the review were assessed for bias using the
risk of bias criteria developed by Cochrane’s EPOC group (21) which is based upon
Cochrane’s Risk of Bias Tool (22). Studies were assessed with regard to selection bias,
performance bias, detection bias, attrition bias, reporting bias, and other sources of bias.
Studies were rated as “low risk of bias (L)”, “high risk of bias (H),” or “unclear risk of bias
(U)” on a general impression after evaluating all criteria (Table 1).
IV. Results: The initial electronic data search yielded a total of 872 potentially
relevant studies; of these, 853 were excluded for some reason, and finally 19 trials fully met
the selection criteria based on inclusion of information regarding comparative data on the pain
scales, and specific populations’ preferences on the scales (Fig. 2). The main reason for
exclusion (33.7%, 288/853) was that irrelevance to comparison of pain scales and scores,
followed by pediatric studies (32.1%, 274/853).
Data collected for the review of the 19 clinical studies included in the analysis of the
pain scales used in the acute setting were tabulated and summarized (Table 1). With respect to
quality of evidence per GRADE guidelines, there were 12 (63%) moderate quality (B) and 7
(37%) low quality (C) evidence derived from the studies.
V. Discussion: In order to use pain-rating scales well clinicians need to appreciate the
potential for error within the tools, and the potential they have to provide the required
information. Interpretation of the data from a pain-rating scale is not as straightforward as it
might first appear. Leigheb M, et al. pointed out that there is substantial discordance between
NRS and VAS scores which is suggestive of a need for clinical judgment to be incorporated

into assessment of actual pain intensity and concluded that leaning on pain scale data alone is
not a comprehensive approach (23).
In the present study, most of the studies in the analysis indicated a good correlation
between VAS, VRS/VDS and NRS, although some pointed out there is a discrepancy in some
situations. One study reported a moderate agreement between calculated percentage pain
reduction from a VAS or NRS and the difference could range up to 30%.
VDS and NRS were also found to have strong correlation and can be used in practice
depending on the preference. The elderly were found to prefer VDS to express their pain
intensity (24, 25) including those with mild to moderate cognitive impairment. Accordingly,
Ware et al. reported that NRS was the preferred scale in the cognitively intact group while
FPS-R was the preferred scale in the cognitively impaired group (26).
A number of studies cited a considerable difficulty in practical use of VAS, especially
in the elderly and populations with disadvantages. For example, Yazici et al. noted that the
NRS, TPS, FPS, and VDS were appropriate pain rating scales for the participants in this
study, and that the VAS should be used in combination with one of these scales (27).
One of the first reviews on comparison of the three pain scales (VAS, VRS, and NRS)
were published by Williamson and Hoggart in 2005 and they reported that
all three scales were valid, reliable and appropriate for use, although the VAS had more
practical difficulties than the other two scales (28). They stressed that for general purposes the
NRS has good sensitivity and produces data that can be analysed for audit purposes.
Likewise, Hjermstad MJ, et al. performed a systematic review of studies to culminate data on
the use and performance of unidimensional pain scales (29). They reported that when
compared with the VAS and VRS, NRSs had better compliance in 15 of 19 studies reporting
this, and were the recommended tool in 11 studies. Overall, NRS and VAS scores
corresponded, with a few exceptions of systematically higher VAS scores.
Limitations of this article are similar to all review articles: the dependence on
previously published research and availability of references. There is also a lack of published
Level I and Level II studies specific to this topic in the world’s literature.
VI. Summary and conclusion
“Pain cannot be treated if it cannot be assessed”. The most important principle is that
clinicians should somehow assess their patients’ pain levels, no matter which method or scale
one uses to accomplish this task. Special scales developed and validated for patients with

difficulties in communication should be made available, and ED physicians should have a
plan for assessing pain in different case scenarios.
The bulk of evidence published to date have demonstrated a gap for improvementto
indicate pluses and minuses of each rating scale used for acute pain. Reports focus that
although all pain-rating scales are valid, reliable and appropriate for use in emergency setting,
the VAS has somehow appeared more difficult than the others. Elderly patients and those with
cognitive impairment, communication problems and minorities have found verbal descriptor
or rating scales more practical than others in expression of their pain intensity. Ongoing
research in the area of ED patient pain management along with usability of each tool should
be conducted on specific patient groups and populations before firm conclusions could be
drawn.

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