Eleven studies from India (Yusufji et al. 1973; Pathak et al. 2007; Yajnik et al.
2008; Krishnaveni et al. 2009; Katre et al. 2010; Veena et al. 2010), Nepal (Bondevik et
al. 2001; Jiang et al. 2005) and Bangladesh (Hall et al. 2007; Li et al. 2008; Lindstrom
et al. 2011) were included in the review; 3 longitudinal and 8 cross-sectional studies.
The number of participants ranged from 101 to 1165 pregnant and the mean maternal
age ranged from 22.6 to 27 years old. Only 2 studies reported the use of multivitamins
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Table 2.6: Shows the methodological overview of studies included in the review : Middle Eastern countries
References Country/ time period
Study Design
Subjects Period of blood collection Maternal age (years) Vitamin B12 measurement method/ blood sample B12 supplement prior to blood sample Q/A score L CS
Ackurt et al., 1995 Turkey Feb - Dec 1991
L 130 pregnant 13-17 wks. (n = 130) 28-32wks. (n = 88)
23.7 ± 4 (16 - 35)
RA/ Non-fasting plasma N/R (+) Koc et al., 2006 Turkey
Before 2004
CS 180 parturient Delivery (38 - 42 wks.) Cord
27 ± 5.8 electrochemiluminiscence method/ Non-fasting serum
19% used multivitamins
6 Ipciglu et al., 2007* Turkey CS 186 pregnant 2nd trimester (n = 58)
3rd trimester (n = 98) 19 - 35 Microparticles enzyme immunoassay/ Fasting serum N/R 5 Abdelrahim et al., 2009 Sudan 2007-2008 CS 279 pregnant; 55 non-anemic
Delivery 25.9 ± 6.4 Immunofluorescent assay/ Serum
N/R 6
Hussein et al., 2009 Egypt CS 84 mother- newborn pairs Delivery Cord 26 ± 0.5 (16 - 42) Automated Chemiluminescent/ Serum N/R 6
Haliloglu et al., 2010* Turkey L 68 pregnant 1st trimester (11 wks.) 2nd trimester (25 wks.) 3rd trimester (32 wks.)
23 - 31 Iluminescence method/ Fasting serum
No (+)
Values represent are mean ± SD (range), RA = radioassay, CS = cross-sectional study, L= longitudinal study, Q/A = quality assessment, quality score for L are: ( - ) = few criteria fulfilled, (+) some criteria fulfilled and (++) most criteria fulfilled, uality score for S are ≥ 6 = high uality and < 6 = low uality, N/R = not reported, *provided vitamin B12 insufficiency (%) in total during pregnancy.
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Table 2.7: Shows the methodological overview of studies included in the review : South Asian countries
References Country/ time period
Study Design
Subjects Period of blood collection Maternal age (years) Vitamin B12 measurement method/ blood sample B12 supplement prior to blood sample Q/A score L CS
Yusufji et al., 1973 India 1966-1968
CS 1000 pregnant 3rd trimester 25.3 (15 - 35) MBA/ Serum N/R 6 Bondevik et al., 2001 Nepal
1994-1995
CS 328 pregnant 18.5 wks. 22.6 (15 - 36) MSA/ Non-fasting serum
No 7
Jiang et al., 2005 Nepal 1998-2001
CS 1165 pregnant 10.9 ± 4.6 23.6 ± 6.0 (15 - 45)
MBA/Serum No 7
Pathak et al., 2007 India CS 283 pregnant ≥ 28 wks 22.9 ± 3.3 MBA/Serum N/R 6 Hall et al., 2007 Bangladesh
2004-2005 CS 101 pregnant Delivery Cord 26 ± 5.3 (16.7 - 39) RIA/Plasma N/R 5 Yajnik et al., 2008 Indian
1994-1996
L 797 pregnant 18 ± 2 wks. 28 ± 2 wks.
21 [19, 2 ]‡ MBA/ Fasting plasma N/R (++) Li et al., 2008 Bangladesh
Jan. - Dec. 2002
L 753 pregnant 8 wks. † 14 wks.
27 (14 - 44) RA/Plasma N/R (+) Krishnaveni et al., 2009 India
1997-1998
CS 774 pregnant; 35 GDM
30 ± 2 wks. N/R MBA/Fasting serum Yes (30%) 7 Veena et al., 2010 India
1997-1998
CS 830 pregnant 30 ± 2 wks. 23.9 ± 4.2 MBA/Fasting plasma N/R 7 Katre et al., 2010 India
2004-2006 L 184 pregnant; 94 rural, 90 urban Mean 17 (12 - 22) Mean 28 (24 - 0) † Mean 34 (32 - 6) †
22.8 ± 3.7 MBA/Fasting plasma Yes (45%) (++)
Lindstrom et al., 2011 Bangladesh Jan. - Dec. 2002
CS 738 pregnant; 523 non-anemic
14.5 ± 1.8 26.6 ± 5.9 RIA/Plasma N/R 7 Values represent are mean ± SD (range), ‡ median [25th
– 75th], MBA = microbiological assay, RIA = radioimmunoassay, RA = radioassay, MSA = Magnatic separation assay, CS = cross-sectional study, L= longitudinal study, Q/A = quality assessment, quality score for L are: ( - ) = few criteria fulfilled, (+) some criteria fulfilled and (++) most criteria fulfilled, uality score for S are ≥ 6 = high uality and < 6 = low uality, N/R = not reported, † B12 insufficiency (%) was not presented at this period.
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2.3.1.2. Study quality assessment
The present review included 15 longitudinal and 42 cross-sectional studies.
According to the type of study design, we used a suitable quality assessment
checklist, as previously discussed in the Method, to identify the level of
methodological quality. The last column of the methodological overview tables
(Tables 2.1 to 2.7) present the total quality score for studies included in the review. From the total longitudinal studies included in the review, 3 studies
(Takimoto et al. 2007; Yajnik et al. 2008; Katre et al. 2010) met most of the quality
assessment criteria, 10 studies met some and 2 studies (Lowenstein et al. 1960;
Whiteside et al. 1968) met few of the assessment criteria. Details of the quality
assessment of these studies are presented in Tables 1 and 2 in Appendix III. Most of the studies reported a clear research question, defined target and study population,
location, stated eligibility criteria, number of participants at the beginning of the
study, issues of selection in to the study methods of data collection, type of analyses
conducted, reported the absolute effect size and related their results back to the target
population. While issues related to consenting (number of consenters and reasons for
non-consenting, comparisons of consenters with non-consenters in terms of baseline
demographic or clinical features) and analysis (loss of follow up, missing data and
confounders accounted into the analysis) were poorly reported. Other items such as
reliability and validity of measurement method were both reported only in
(Lowenstein et al. 1960; Brabin et al. 1986; Murphy et al. 2007), while reliability
alone was reported in (Knight et al. 1991; Katre et al. 2010) and validity was
reported only in (Pagán et al. 2002; Takimoto et al. 2007). Furthermore, relative
effect size was only reported in (Pagán et al. 2002; Takimoto et al. 2007; Katre et al.
59
quantitatively; however, only 4 studies reported it qualitatively (Takimoto et al.
2007; Li et al. 2008; Yajnik et al. 2008; Katre et al. 2010). Finally, issues on the
generalizability of the results was only discussed in (Ackurt et al. 1995; Milman et
al. 2006; Yajnik et al. 2008).
From the total cross-sectional studies included in the review, 60% (n = 25) of
the included studies scored positively on more than 75% on the quality items in the
assessment checklist and were rated as a high quality studies. Fifteen studies scored
between 44% and < 75% and only 2 studies scored 43%, though both were rated as
low quality studies. Details of the quality assessment of these studies are presented in
Tables 1 to 7 in Appendix IV. Most of the studies clearly defined their objectives, issues related to the study population and outcome measures were also well
identified, while adjusting the results for possible confounders in the analysis were
varied and assessed in 14 studies only. Six studies (Ball and Giles 1964; House et al.
2000; Schulpis et al. 2004; Garcia-Casal et al. 2005; Hall et al. 2007; Ray et al.
2008) did not assess the outcome measures (serum vitamin B12 and folate) from new
participants. In addition, the exposure assessment item was not applicable for all the
included studies according to the aim of the present review.