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RESEARC H ARTIC LE Open Access
Oral vitamin B12 for patients suspected of subtle
cobalamin deficiency: a multicentre pragmatic
randomised controlled trial
Bernard Favrat
1*†
, Paul Vaucher
1,2†
, Lilli Herzig
2
, Bernard Burnand
3
, Giuseppa Ali
1
, Olivier Boulat
4
,
Thomas Bischoff
2
, François Verdon
2
Abstract
Background: Evidence regarding the effectiveness of oral vitamin B12 in patients with serum vitamin B12 levels
between 125-200 pM/l is lacking. We compared the effectiveness of one-month oral vitamin B12 supplementation
in patients with a subtle vitamin B12 deficiency to that of a placebo.
Methods: This multicentre (13 general practices, two nursing homes, and one primary care center in western
Switzerland), parallel, randomised, controlled, closed-label, observer-blind trial included 50 patients with serum
vitamin B12 levels between 125-200 pM/l who were randomized to receive either oral vitamin B12 (1000 μg daily,
N = 26) or placebo (N = 24) for four weeks. The institution’s pharmacist used simple randomisation to generate a
table and allocate treatments. The primary outcome was the change in serum methylmalonic acid (MMA) levels
after one month of treatment. Secondary outcomes were changes in total homocysteine and serum vitamin B12
levels. Blood samples were centralised for analysis and adherence to treatment was verified by an electronic device
(MEMS; Aardex Europe, Switzerland). Trial registration: ISRCTN 22063938.
Results: Baseline characteristics and adherence to treatment were similar in both groups. After one month, one
patient in the placebo group was lost to follow-up. Data were evaluated by intention-to-treat analysis. One month
of vitamin B12 treatment (N = 26) lowered serum MMA levels by 0.13 μmol/l (95%CI 0.06-0.19) more than the
change observed in the placebo group (N = 23). The number of patients needed to treat to detect a metabolic
response in MMA after one month was 2.6 (95% CI 1.7-6.4). A significant change was observed for the B12 serum
level, but not for the homocysteine level, hematocrit, or mean corpuscular volume. After three months without
active treatment (at four months), significant differences in MMA levels were no longer detected.
Conclusions: Oral vitamin B12 treatment normalised the metabolic markers of vitamin B12 deficiency. However, a
one-month daily treatment with1000 μg oral vitamin B12 was not sufficient to normalise the deficiency markers for
four months, and treatment had no effect on haematological signs of B12 deficiency.
Background
Vitamin B12 deficiency (less than 150 pM/l) is common
in elderly people, with the reported prevalence ranging
from 15% to 20% [1,2]. Most patients show no evidence
of megaloblastic anaemia; however, these patients are still
at risk for neurological abnormalities [3]. Furthermore,
vitamin B12 deficiency leads to hyperhomocysteinemia,
an independent risk factor for ischemic heart disease [4]
and dementia [5]. Comparisons between patients with
known complications and “normal”control patients [6]
have produced several definitions of cobalamin defi-
ciency. Over the past 15 years, the definition of vitamin
B12 deficiency has included determination of two
metabolites due to their favourable sensitivities and spe-
cificities: serum methylmalonic acid (MMA) and homo-
cysteine (Hcys) [7,8]. Over the past few decades, a
number of publications and two randomised controlled
trials have demonstrated that oral B12 is as efficacious as
* Correspondence: bernard.favrat@hospvd.ch
†Contributed equally
1
Department of Ambulatory Care and Community Medicine, University of
Lausanne, Bugnon 44, CH-1011 Lausanne, Switzerland
Full list of author information is available at the end of the article
Favrat et al.BMC Family Practice 2011, 12:2
http://www.biomedcentral.com/1471-2296/12/2
© 2011 Favrat et al; licensee BioMed Central Ltd. This is an Open Access article distributed u nder the terms of the Creat ive Commons
Attribution L icense (http://creati vecommons.org/licenses/by/2.0), which perm its unrestricted use, di stribution, and reproduction in
any medium, provided the original work is properly cited.
intramuscular injection, especially for normalising meta-
bolic markers of cobalamin deficiency [9-13], and is also
cost-effective [14].
Nevertheless, there is a lack of randomised placebo-
controlled trials to validate the use of oral vitamin
B12 therapy [15]. Furthermore, few randomised placebo-
controlled trials have evaluated the biological impact of
oral therapy (1000 μg/d) in general practice for border-
line serum vitamin B12 concentrations (125-200 pM/l)
among patients without pernicious anaemia [16,17]. Our
objective was to evaluate the efficacy of oral cobalamin in
reducing MMA levels in patients suspected of vitamin
B12 deficiency but with borderline vitamin B12 concen-
trations. This type of study is important for helping to
determine whether the MMA level “indicates or predicts
a clinical condition in need of treatment”[18].
Methods
A pragmatic [19,20], placebo-controlled, randomised
controlled trial with a four-month follow-up period
was conducted by 16 general practitioners in the wes-
tern part of Switzerland between October 2002 and
September 2004. The study protocol was approved by
the ethics review committee for clinical research of
the Department of Internal Medicine, University of
Lausanne, and was registered in the Current Controlled
Trial Database (ISRCTN 22063938).
Participants
Physicians enrolled patients from private practices (13
general practitioners), an academic primary care centre
(counted as one general practitioner), and nursing
homes (two general practitioners). Patients in whom
physicians suspected B12 deficiency based on clinical
parameters were asked to participate. Patients who were
suspected of having cobalamin deficiency met at least
one of the following inclusion criteria: history of
cobalamin deficiency, red cell macrocytosis (>99 fl), or
neurological or psychiatric symptoms (or both) defined
as having three or more positive responses to the symp-
toms described in Table 1.
Consenting patients with serum vitamin B12 levels
equal to or greater than 125 pM/l but equal to or less
than 200 pM/l were included. Exclusion criteria
included folate deficiency, renal insufficiency, and folate
or vitamin B12 treatment during the preceding six
months. For ethical reasons, patients with vitamin B12
levels less than 125 pM/l after one month received oral
vitamin B12 supplementation for one month. Written
informed consent was obtained from all patients before
screening for vitamin B12 deficiency. Details of refusal,
exclusion, dropouts, and missing data were collected
when available. Blood samples and baseline values were
collected before treatment allocation. All blood samples
were centralised and analysed using a single analysis
method.
Treatment, randomisation, blinding, and adherence to
therapy
Participants received either 1000 μg oral vitamin B12
(cobalamin) or placebo daily for four weeks. An inde-
pendent pharmacist delivered active or placebo pills
according to a prior, simple computer-generated rando-
misation list. The active and placebo pills were similar
in appearance and taste and were given in a similar con-
tainer. Patients, caregivers, investigators, and the statisti-
cian were blinded to treatment until the end of the trial.
Each drug package was coded with a unique number
according to the randomisation schedule, then sent to
the relevant practice. The codes were held by the phar-
macists and remained unbroken until the analysis was
completed. Patients were asked not to take any other
vitamin supplements, and the treating physician verified
this at the one- and four-month follow-up visits.
Table 1 Reasons for patient eligibility reported by physicians (N = 49*)
Symptoms Oral B12 (N = 26) N(%) Placebo (N = 23*) N (%)
“Do you have a pins and needles feeling in your feet?”or “Do you have a compelling
urge to move your legs in the evening or at night?”
10 (38%) 7 (30%)
“Have you recently felt unsteady when walking for reasons other than your rheumatism
or after having an accident?”
5 (19%) 3 (13%)
“During the past month have you often been bothered by feeling down, depressed,
or hopeless?”and “During the last month, have you often been bothered by having little interest
or pleasure in doing things? [41]
7 (27%) 8 (35%)
“Did you feel that you were losing your memory or has someone mentioned this to you lately?”5 (19%) 4 (17%)
“Has your character changed lately or has someone mentioned this to you?”2 (8%) 3 (13%)
“Has it been more difficult for you to perform your usual activities,
such as reading a book, watching TV, writing, paying bills, doing your housework, etc.?”
5 (19%) 6 (26%)
Anemia detected (blood formula) 4 (15%) 6 (26%)
Macrocystosis (blood formula) 4 (15%) 5 (21%)
* One questionnaire was not returned by the physician.
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Outcomes
Theprincipleoutcomewastherelativedifferencein
serum MMA levels at baseline and after one month of
treatment. Responders were defined as those partici-
pants exhibiting more intra-individual variation in
MMA (a decrease in the serum MMA level greater than
0.076 μmol/l) than that caused by random variation
[21]. Secondary outcomes were changes in serum vita-
min B12 levels, total Hcys levels, and clinical improve-
ment based on symptoms and physical signs at the one-
and four-month follow-up visits. Changes in MMA
levels measured at baseline and after four months were
also determined. The relative improvement toward the
population mean value and the number of patients
needed to treat (NNT) were reported as secondary out-
comes for MMA. Haematological improvement was
measured for mean corpuscular volume and hematocrit.
Cognitive changes were assed using the Mini Mental
State Examination (scale ranging from 30 to 0).
Measurements and laboratory methods
Medical visits and blood sampling were performed by
physicians at baseline and after one and four months.
Participants participated in a structured interview to
record socio-demographic variables, medical history,
complaints, the reason why the physician suspected vita-
min B12 deficiency, medication, importance of neurolo-
gical or psychiatric signs, and state of health.
Blood samples were drawn by standard antecubital
venipuncture from patients who were not fasting. Two
separate tubes were collected; all tubes were centralised
for analysis in a single laboratory. Samples were centri-
fuged and serum concentrations of MMA, Hcys, creati-
nine, vitamin B12, and folate were measured. Renal
insufficiency was defined as a serum creatinine level
greater than 97 μmol/l, folate insufficiency as a serum
value below 7 nmol/l, and red cell macrocytosis as a
value greater than 99 fl. Haematological parameters
were measured by an automated analyser (Sysmex XE-
2100; Sysmex corporation, Hyogo, Japan). Serum creati-
nine levels were measured by the Jaffé kinetic method at
37°C (Modular ANALYTICS system; Roche Diagnostics,
Basel, Switzerland). Serum vitamin B12 and folate levels
were measured by a quantitative radioimmunoassay
using purified intrinsic factor and purified folate-binding
protein. MMA levels in serum were determined by gas
chromatography and mass spectrometry with isotopic
dilution. Analytical performance was assessed by inter-
nal and external quality controls (ERNDIM; http://www.
erndimqa.nl/). Typical coefficients of variation were less
than 3.8% at 0.39 μmol/l (N = 55) and less than 3.7% at
1.75 μmol/l (N = 61). Total Hcys levels in serum were
quantified by high performance liquid chromatography
with fluorimetric detection [22]. Typical coefficients of
variation were less than 5.2% at 5.5 μmol/l (N = 120)
and less than 3.3% at 16.4 μmol/l (N = 143). Adherence
to treatment was verified by an electronic device
(MEMS; Aardex Europe, Switzerland) that recorded the
date and time of every opening of the pill container.
Unused pills were also counted. Adherence was quanti-
fied by calculating the percentage of days that the pill
container was opened once.
Statistical methods
Our study was powered to detect a mean decrease in
MMA values of 0.2 μmol/l in the treatment group as
compared with 0.05 μmol/l in the placebo group.
Expecting a standard deviation of 0.15 μmol/l with the
significance level set at p < 0.05 and power set at 0.8,
the estimated sample size was 16 participants in each
group. Based on previous data [23], we estimated that
the proportion of responders (as determined by a
change in MMA) would be 10% in the placebo group
and at least 50% in the intervention group, necessitating
the inclusion of 25 patients in each group.
We performed the principal analysis according to inten-
tion to treat (all patients remained in their initially
assigned arm). The planned measure of magnitude of
effects was absolute change difference from baseline
between the treatment and placebo arms. This difference
was determined by computing the least square means of
differences with linear regression, adjusting for baseline
value. Robust standard error [24] was used to take hetero-
scedasticity into consideration. To control for the observed
lack of homogeneity of variance for different baseline
values, we also computed the improvement from baseline
in proportion to what would have been expected had the
values become normal (relative improvement). This sec-
ondary measure of intervention effect was the relative
improvement difference between arms (RΔ%). Based on
previously published information, we considered the
healthy population’s mean MMA value to be 0.17 μmol/l
[25], the mean Hcys value to be 10.2 μmol/l [25], and the
mean vitamin B12 value to be 375 pM/l [26]. If the values
changed to exceed the mean population value, the mea-
sure of effect was limited to 1.0. If no improvement was
detected at follow-up, or if the baseline values were already
normal, the measure of effect was considered null. Stu-
dent’st-test was used to evaluate the significance of the
observed difference between those patients receiving B12
and those receiving placebo. No measures were taken to
control the overall type I error rate because outcomes
were expected to be highly correlated to each another.
The NNT was calculated considering dropouts and miss-
ing data as non-responders. We set the alpha level to 0.05
and calculated 95% confidence intervals (CIs). All statisti-
cal analyses were performed using Stata 10.0 (StataCorp
LP, College Station, TX, USA).
Favrat et al.BMC Family Practice 2011, 12:2
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Results
Vitamin B12 deficiency was suspected in 81 patients.
Three patients refused to participate (4%) without pro-
viding reasons, 14 (17%) had B12 serum values less than
125 pM/l and were given B12 treatment, and 14 (17%)
had serum values greater that 200 pM/l and were
excluded. The 50 remaining patients were randomly
assigned (Figure 1) to the placebo arm (N = 24) or the
experimental arm (N = 26). The symptoms that most fre-
quently made the physician suspect B12 deficiency were
paraesthesia and depression (Table 1). Age, sex, and
other characteristics were similar between the groups
(Table 2). Doses and proportion of days with correct
medication were 27.4 intakes and 93.5% of days for the
oral B12 group and 28.4 intakes and 94.4% of days for
the placebo group. Seven patients (one from the
treatment group) had vitamin B12 levels less than 125
pM/l at one month and received oral vitamin B12 supple-
mentation for one extra month. These patients were
included in the intention to treat analysis. One question-
naire was not completed by the physician. Transport
inconvenience prevented 18/145 blood samples (from 13
patients) from being analysed for metabolites. Six of 50
electronic devices used to measure treatment compliance
were not returned; thus, adherence data were missing for
these patients. We observed no relevant side effects of
treatment during the four-month follow-up period. Two
adverse events were reported, both in the intervention
group. One patient was hospitalised for psychiatric rea-
sons and one was hospitalised to receive a blood transfu-
sion. Physicians considered both of these events
unrelated to vitamin B12 administration.
Figure 1 Flow chart of the study design. * B12 concentration was not available for one patient who was assumed not to be deficient. Hcys:
homocysteine, MMA: methylmalonic acid.
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At baseline, 21.7% of patients had MMA levels that
were considered normal (less than 0.26 μmol/l). Serum
concentrations of metabolites at baseline, one month,
and four months appear in Figure 2. A significant treat-
ment effect was observed on surrogate values of serum
vitamin B12 after both one and four months, and on
MMA values at one month (Table 3). Per-protocol ana-
lysis also confirmed the absence of a difference in mean
MMA concentrations between the placebo and treat-
ment groups at four months (-0.02 μmol/l; 95% CI -0.16
to 0.13; p = 0.832). We also measured the relative
improvement effect toward the healthy population’s
mean value (Table 4). At one month, patients under-
going vitamin B12 treatment decreased their mean defi-
cit by 48.7% (95% CI 29.0 to 68.3) over placebo. Finally,
the NNT for improving MMA serum concentration at
one month was 2.6 patients (95% CI 1.7 to 9.4).
Discussion
This study has demonstrated that in primary care
patients with nonspecific symptoms and borderline
serum vitamin B12 levels, serum MMA levels were cor-
rected more often in patients receiving one month of
oral cobalamin therapy than in patients receiving one
month of placebo. However, the benefit to the MMA
level disappeared after three additional months without
cobalamin therapy.
Although treatment has been deemed necessary
regardless of laboratory results for patients with signs of
severe cobalamin deficiency [27,28], in general practice
one might question the impact of treatment for patients
with nonspecific symptoms suspected to be related to
cobalamin deficiency. The definition of cobalamin defi-
ciency remains imprecise; a definition based only on
clinical symptoms lacks specificity up to advanced
stages, except in cases of pernicious anaemia. Therefore,
a serum vitamin B12 level below 125 μmol/l cannot be
the sole criterion for defining cobalamin deficiency. No
clear cut-off values have been defined, and publications
have variously asserted that there are “grey areas”below
295 pM/l [29], 200 pM/l [30], or 250 pM/l [27].
The metabolic markers MMA and Hcys show promise
as markers for improving the diagnosis of cobalamin defi-
ciency [7,8,31]. Our randomised controlled trial showed
an improvement in MMA levels and a nonsignificant fall
in Hcys following oral B12 supplementation for one
month (Table 3). For MMA, our results corroborate
observations from three other pertinent trials [17,32] and
one equivalent trial comparing oral to parenteral admin-
istration [12]. However, our study is the first to follow
patients after cessation of treatment. Our findings sug-
gest that one month of treatment is not enough to main-
tain MMA serum concentrations above borderline
deficit. Furthermore, one month of treatment may not be
sufficient to affect Hcys levels, as other studies have
demonstrated improvement after treatment periods of
three months [33]. The specificity of Hcys is considered
low, which may also explain the low response of Hcys
levels to vitamin B12 therapy [27]. Hcys levels are also
influenced by lifestyle habits (coffee, alcohol, and smok-
ing), renal function, genetic abnormalities, and folate
deficiency.
In the primary care setting, the importance of subtle
cobalamin deficiency and its related clinical impact
remain under debate. Increased concentrations of MMA
metabolites in patients without anaemia define subtle
cobalamin deficiency [29]. The prognostic and clinical
significances of this state are not clear [34]. Neuropathy,
anaemia, and cognitive impairment are possible
[15,35,36], and some observational studies have demon-
strated a clinical benefit from treatment, including oral
therapy [15,35]. However, Solomon found patients with
Table 2 Baseline characteristics of study participants
Oral B12 (N = 26) Placebo (N = 24)
Gender (Female) 14 (53.8%) 13 (54.2%)
n (%)
Age
Mean (SD) 69.6 yrs (SD = 18.8) 68.6 yrs (SD = 18.5)
Median (range) 76 yrs (31 - 91) 75 yrs (18 - 88)
Serum B12
Mean (SD) 164 pM/l (SD = 24) 154 pM/l (SD = 20)
Median (range) 164 pM/l (127 - 203) 150 pM/l (126 - 191)
Serum MMA
Mean (SD) 0.43 μmol/l (SD = 0.25)* 0.41 μmol/l (SD = 0.24)*
Median (range) 0.32 μmol/l (0.19 - 1.1) 0.31 μmol/l (0.15 - 0.92)
MMA ≥0.26 μmol/l
n (%) 18 (83.3%)* 16 (72.7%)*
Serum HCys
Mean (SD) 18.3 μmol/l (SD = 6.6)* 15.0 μmol/l (SD = 5.3)*
Median (range) 18.1 μmol/l (9.8 - 31.5) 14.3 μmol/l (7.5 - 27.1)
Hematocrit
Mean (SD) 40.3% (SD = 4.2)
†
39.5% (SD = 4.6)
Median (range) 39.5% (32 - 46) 40% (27 - 47)
Mean corpuscular
volume
Mean (SD) 91.2 fl (SD = 9.2)
†
92.6 fl (SD = 5.1)
Median (range) 90 fl (63 - 100) 92 fl (81 - 111)
Serum creatinine
Mean (SD) 96.4 μmol/l (SD = 27.9) 89.0 μmol/l (SD = 27.2)
Median (range) 86 μmol/l (60 - 160) 89 μmol/l (37 - 137)
Serum folic acid
Mean (SD) 16.6 nmol/l (SD = 9.1) 19.2 nmol/l (SD = 10.9)
Median (range) 16.2 nmol/l (5.6 - 45.3) 14 nmol/l (5.4 - 33)
Hcys = homocysteine, MMA = methylmalonic acid, SD = standard deviation.
* Transport inconvenient generated missing total at random data; samples
were not analysed for 2 patients in the oral B12 group and for 2 patients in
the placebo group.
†
One physician did not report results from the blood formula onto the case
report form. Data were unvailable for one patient in the oral B12 group.
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100
150
200
250
300
400
500
600
Baseline 1 month 4 months
Serum B12 pM /l (log scale)
Oral B12 (1 month)
Baseline 1 month 4 months
Placebo
B12
Oral B12 (1 month) Placebo
0.5
1.0
2.0
m
ol/l (log scale)
MMA
0.75
1.5
B
12
MMA
Baseline 1 month 4 months
Baseline 1 month 4 months
0.25
MMA μ
μ
μ
μ
m
Baseline 1 month 4 months
Oral B12 (1 month)
Baseline 1 month 4 months
Placebo
10
15
20
25
40
Hcys mol/l (log scale)
30
50
HCy
Hcys
μ
μ
μ
μ
Figure 2 Changes in metabolic values. Red dotted lines correspond to patients from the placebo group who received vitamin B12 for one
month at the one-month follow-up. Hcys: homocysteine, MMA: methylmalonic acid.
Table 3 Different outcomes in the oral B12 treatment group and the placebo group after one and four months
Oral B12 Placebo Impovement from baseline between oral B12 and
placebo*
Biological marker 1 month Mean
(SD); N
4 months Mean
(SD); N
1 month Mean
(SD); N
4 months Mean
(SD); N
1 month* Δ(CI95%;
p-value)
4 months* Δ(CI95%;
p-value)
MMA (μmol/l) 0.23 (0.08); 22 0.41 (0.30); 19 0.37 (0.14); 23 0.35 (0.16); 22 - 0.13 (CI95% -0.19 to -0.06;
p < 0.001)
0.03 (CI95% -0.12 to 0.17;
p = 0.686)
Serum cobalamin
(pM/l)
263.4 (89.8); 25 202.6 (56.3); 23 154.5 (41.1); 24 162.9 (39.8); 23 101.6 (CI95% 60.1 to 143.2;
p < 0.001)
35.0 (CI95% 6.4 to 63.5;
p = 0.018)
Hcys (μmol/l) 16.5 (6.1); 22 17.1 (7.5); 19 13.9 (4.3); 23 15.6 (5.8); 22 0.04 (CI95% -1.2 to 1.3;
p = 0.950)
-1.0 (CI95% -4.0 to 2.0;
p = 0.502)
Hematocrite (% red
cells)
39.6 (4.1); 26 40.1 (4.0); 26 39.7 (4.6); 24 39.4 (4.6); 22 -0.4 (CI95% -1.7 to 0.8;
p = 0.502)
0.5 (CI95% -1.0 to 2.1;
p = 0.475)
MCV (fl) 89.8 (6.9); 26 89.0 (7.0); 26 92.8 (7.0); 24 92.6 (7.6); 22 -0.4 (CI95% -2.2 to 1.4;
p = 0.674)
-0.1 (CI95% -2.3 to 2.2;
p = 0.950)
MMSE (score 0-30) - 27.8 (2.3); 26 - 28.1 (2.2); 21 - -0.4 (CI95% -1.3 to 0.6;
p = 0.432)
* Least square means were computed using linear regression with robust standard error to take heteroscedasticity into account. Each value at 1 or 4 months was
introduced separately as the dependent variable, with group allocation and baseline value as independent variables. Interpretation of these magnitudes is
nevertheless restricted. Variance is not constant across baseline values (heteroscedasticity). Effects are more important for patients with initial higher levels of
deficiency. Hcys = homocysteine, MMA = methylmalonic acid, MMSE= Mini Mental State Examination.
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clinical signs of cobalamin deficiency but normal levels
of metabolic markers [34]. In a randomised controlled
trial in community-dwelling subjects, Lewerin found
that four months of oral 0.5 mg vitamin B12 in combi-
nation with folic acid and vitamin B6 normalised
serum MMA and Hcys levels, but failed to improve
movement and cognitive performance [37]. Hvas also
reported limited clinical improvement following
administration of vitamin B12 to patients with elevated
MMA (0.4-2 μmol/l) levels [18,34,38]. However, con-
troversy continues to surround the question of whether
vitamin B12 supplements affect cognition [39]. In our
study, one month of oral vitamin B12 significantly
increased serum cobalamin levels, but the effect did
not persist after three more months without supple-
mentation. These results are unexpected, given the
liver storage capacity for vitamin B12 and the quantity
of B12 administered during this study, and the effec-
tiveness of intermittent treatment remains uncertain.
Surrogates alone may not provide sufficient evidence
to assume clinical benefits of vitamin B12 supplemen-
tation. Further studies are required to assess the effects
on clinical outcomes.
One limitation of our study lies in defining the popu-
lation for which our results are applicable. Further ran-
domised trials are still necessary to evaluate the
prophylactic effect of oral B12 for preventing neurologi-
cal manifestations [40]. Mishandling of blood samples
resulted in the loss of some data. These unexpected
events and other missing data were not included in our
initial sample size estimation, limiting the power of our
study. Most missing data were missing completely at
random, our results were therefore not biased, and only
the power of the study was diminished. Finally, the
inclusion of essentially non-anaemic patients who are
less likely to respond to vitamin B12 treatment may
affect our ability to generalise our results to an anaemic,
cobalamin-deficient population.
Conclusion
Although oral B12 therapy evoked an important meta-
bolic response, this response did not persist for an addi-
tional three months following cessation of therapy,
causing us to question whether extending oral vitamin
B12 treatment beyond one month would have a signifi-
cant effect on the clinical manifestations of cobalamin
deficiency. Whether correcting abnormal metabolic mar-
kers in hopes of improving clinical symptoms in patients
with suspected borderline cobalamin deficiency is a
clinically auspicious strategy remains under debate.
List of abbreviations
Hcys: homocysteine; MMA: methylmalonic acid; NNT: number needed to
treat; SD: standard deviation; RΔ%: relative reduction difference towards the
healthy population’s mean value
Acknowledgements
We thank the general practitioners who served as local investigators,
without whom this study would not have been possible. We thank the
institution’s pharmacy for preparing the randomisation list, sending the
appropriate material to each physician, and for managing the electronic
devices measuring compliance. We thank Françoise Secretan, research nurse,
for her meticulous work as data manager. We also thank Streuli Pharma AG,
Uznach, Switzerland, for preparing pills (placebo and active) and providing
them to us for this study.
Author details
1
Department of Ambulatory Care and Community Medicine, University of
Lausanne, Bugnon 44, CH-1011 Lausanne, Switzerland.
2
Institute of General
Medicine, University of Lausanne, Bugnon 44, CH-1011 Lausanne,
Switzerland.
3
Institute of Social and Preventive Medicine, University of
Lausanne, Bugnon 17, CH-1005 Lausanne, Switzerland.
4
Laboratory of Clinical
Chemistry, Hospices-CHUV, Bugnon 46, CH-1011 Lausanne, Switzerland.
Authors’contributions
BF, FV, LH, BB, GA, and TB designed the study. PV, BF, and FV analysed and
interpreted the data. BF and PV drafted the manuscript. FV, LH, BB, GA, and
TB revised and corrected the draft. All authors read and approved the final
manuscript.
Competing interests
BF, PV, LH, BB, GA, OB, TB, and FV all declare the absence of any financial or
non-financial competing interests.
Received: 16 July 2010 Accepted: 13 January 2011
Published: 13 January 2011
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Pre-publication history
The pre-publication history for this paper can be accessed here:
http://www.biomedcentral.com/1471-2296/12/2/prepub
doi:10.1186/1471-2296-12-2
Cite this article as: Favrat et al.: Oral vitamin B12 for patients suspected
of subtle cobalamin deficiency: a multicentre pragmatic randomised
controlled trial. BMC Family Practice 2011 12:2.
Favrat et al.BMC Family Practice 2011, 12:2
http://www.biomedcentral.com/1471-2296/12/2
Page 8 of 8
