1. Anaemia and iron indicator
Cross-sectional analysis in young non-pregnant and pregnant women in Burkina Faso of associations between biomarkers of iron status and effect modification by inflammation and P. falciparum infection
Anaemia and iron deficiency are highly prevalent globally, and a major cause of morbidity in adolescents and women, especially when pregnant. In West Africa iron deficiency is reported to affect a third of women attending first antenatal visits, and up to 20% of non-pregnant women of reproductive age (1). A limitation of studies estimating prevalence of iron deficiency is the plethora of different indicators of iron status and their interpretation in relation to each other. A further complication is the effect of inflammation on some indices, a significant problem in African countries with a high prevalence of malaria and other infections. Adjustment methods to correct for inflammation are proposed, but the studies are primarily in children.
Background
Methods
Data were derived from a randomised controlled trial of periconceptional weekly iron supplementation among young mostly adolescent nulliparous non-pregnant women and primigravidae living in Nanoro Demographic Surveillance area, Burkina Faso. Data points were at the end assessment (FIN) survey for women who remained non pregnant (N=973), and at the first scheduled antenatal visit (ANC1) for women who became pregnant (N=315).
Plasma ferritin, serum transferrin receptor, and C-reactive protein (CRP) were measured in duplicate by ELISA, zinc protoporphyrin (ZnPP) by fluorometry, and haematological indices by a Sysmex automated analyser.
P. falciparum slide positivity and CRP cut-off points of < 5 µg/ml and < 10 µg/ml were used to define inflammation categories.
Iron deficiency (ID) was defined as ….. Diallo to complete….
Body iron (BI) was calculated from the log10 (sTfR/serum ferritin) using the equation derived by Cook et al: body iron (mg/kg) = - [log10 (1000 x sTfR/ferritin) – ]/ (2).
Statistical analyses were conducted in Stata and EPI info version 7.
Diallo S.1,
Gies S.2,
Rouamba T.1,
Roberts S.A.3,
Ouedraogo G.A.5,
Tinto H.1,
Brabin B.J.4
1 Clinical Research Unit of Nanoro, Burkina Faso;
2 Institute of Tropical Medicine, Antwerp, Belgium;
3Liverpool School of Tropical Medicine, Liverpool, UK;
4Liverpool School of Tropical Medicine and Institute of Infection and Global Health, University of Liverpool, UK; Global Child Health Group, Academic Medical Centre, University of Amsterdam, the Netherlands. 5Université Nazi Boni, Bobo Dioulasso, Burkina Faso.
Objectives
In young non-pregnant and pregnant women living under endemic malaria transmission, estimate iron biomarker correlations, body iron stores, iron deficiency prevalence using single and multiple biomarker definitions, and effect modification by inflammation and P. falciparum parasitaemia.
Results
1. Characteristics of participants
Iron biomarker and/or haematological results were available for 969 non-pregnant (FIN) and 314 pregnant women (ANC1). P. falciparum parasitaemia prevalence was higher at ANC1 than in non-pregnant women at end assessment (relative risk 1.28, 95%CI , P<0.001), and pregnant women had higher parasite density (P <0.001). Mean body iron was 8.3 (95%CI ) in pregnant and 6.0 (95%CI ) in non-pregnant women. Based on the sTfR/log ferritin ratio 13.4% women at ANC1, and 20.6% of non-pregnant women at FIN were iron deficient.
3. Effect of inflammation and P. falciparum parasitaemia
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2. Biomarker correlations
Correlations coefficients were universally higher for non-pregnant than pregnant women, except for CRP. Serum ferritin was positively correlated with haemoglobin in non-pregnant women, whereas pregnant women had an equally significant but negative correlation (Table 1).
Table 1: Biomarker correlation coefficients in pregnant women at ANC1 and non-pregnant women at end assessment
Ferritin
sTfR*
CRP*
ZnPP*
sTfR/log fer* Hb
RDW
MCHC
MCV
Pregnant  
sTfR *
-0.052
0.372c
0.209c
0.018
0.502c
0.307c
sTfR/logfer*
-0.529c
0.871c
-0.004
0.441c
-0.259c
-0.402c
-0.490c
-0.606c
-0.229c
-0.015
0.343c
0.156b
0.481c
0.306c
-0.378c
0.003
-0.239c
0.199c
-0.129a
-0.211c
0.342c
-0.390c
0.247c
0.139c
0.136c
-0.028c
-0.003b
-0.154c
-0.078c
-0.336a
Body iron
0.928c
-0.420c
0.256c
-0.172b
-0.806c
-0.084
-0.144c
0.089
0.172
Non-pregnant
-0.302c
0.087a
0.618c
0.107b
-0.680c
0.899c
-0.020c
0.662c
0.322c
-0.455c
-0.077a
-0.637c
-0.509c
-0.312c
0.421c
0.030
0.568c
0.471c
-0.456c
0.335c
-0.339c
-0.053
0.590c
-0.263c
0.272c
-0.292c
-0.034
-0.405c
-0.354c
0.383c
-0.569b
0.079c
0.936c
-0.617c
0.131c
-0.550c
-0.892
0.433
-0.412c
0.400
0.332
Conclusion
a = P< 0.05; b = P<0.001; c = P<0.0001; * log10-transformed
sTfR: serum transferrin receptor; sTfR/log10fer : sTfR/log10ferritin ratio ; ZnPP: whole blood zinc protoporphyrin; Hb:hemoglobin; RDW: Red cell distribution width; CRP: C-reactive protein; MCV= mean corpuscular volume; MCHC: mean corpuscular hemoglobin concentration; body iron: body iron stores.
Cell sample sizes for pregnant women vary from 282 to 314; for non-pregnant women from 952 to 969.
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Table 2: Prevalence of anaemia and iron categories by CRP levels and malaria
Anaemia and iron indicator
CRP5
No malaria (n)
Malaria (n) P
CRP10
Non-pregnant
Hb < 12, g/L
38.1 (535)
47.7 (358)
0.004
38.3 (553)
48.9 (384)
<0.001
sTfR/log10ferritin ratio >5.6
19.3 (534)
21.9 (356)
0.34
19.4 (550)
20.9 (382)
0.57
ZnPP, µmol/mol heme >85
59.0 (527)
68.4 (358)
59.5 (543)
69.3 (384)
0.002
Pregnant
Hb < 11 g/dL
46.0 (113)
69.6 (46)
0.006
47.6 (126)
73.8 (84)
18.7 (112)
2.2 (46)
16.9 (124)
5.9 (84)
0.02
ZnPP, µmol/mol heme >85
66.7 (105)
88.9 (45)
0.005
66.4 (116)
81.2 (80)
CRP5: women having C-reactive protein concentration < 5 µg/ml; CRP10 women having C-reactive protein <10 µg/ml; ZnPP: zinc-protoporphyrin . Malaria: presence of Plasmodium falciparum infection by microscopy, No malaria: absence of Plasmodium falciparum infection by microscopy
References
(1) Rohner F, Northrop-Clewes C, Tschannen AB, Bosso PE, Kouassi-Gohou V, Erhardt JG, Bui M, Zimmermann MB and Mascie-Taylor CG. Prevalence and public health relevance of micronutrient deficiencies and undernutrition in pre-school children and women of reproductive age in Côte d’Ivoire, West Africa. Public Health Nutr. 2014; 17:
(2) Cook J, Flowers CH and Skikne BS. The quantitative assessment of body iron. Blood 2003;101:
The study was funded by the National Institutes of Child Health and Human Development / Gates Foundation, NICHD grant number (NIH-1U01HD A1),
and the NIH Office of Dietary Supplements to the Liverpool School of Tropical Medicine.