Table 4.

Hb and serum ferritin concentrations in the study participants without haemoglobinopathies at baseline and after the 3·5-month supplementation period, and the difference between baseline and post-supplementation, by areas with low and high iron in the groundwater, Bangladesh, April–October 2015

	High-groundwater-Fe areas (n 203)		Low-groundwater-Fe areas(n 192)
Variable	Mean*	95 % CI	Mean*	95 % CI	P value†
Hb (mg/dl)
Baseline	11·58x	11·44, 11·72	11·29a,y	11·14, 11·44
Post	11·44	11·30, 11·59	11·48b	11·33, 11·62
Change (baseline – post-supplementation)	–0·06	–0·19, 0·07	0·11	–0·03, 0·24	0·101
Serum ferritin (µg/l)‡
Baseline	25·46a,x	22·61, 28·68	18·92y	16·60, 21·57
Post	22·39b,x	20·27, 24·73	17·44y	15·76, 19·30
Change (baseline – post-supplementation)	–4·71	–6·82, –2·60	–7·64	–9·78, –5·51	0·068

^a,bMean values within a column for each of the variables (within each groundwater-Fe area) with unlike subscript letters were significantly different (P < 0·05).

^x,yMean values within a row for each of the variables (at each time point) with unlike subscript letters were significantly different (P < 0·05).

^*Repeated-measures ANOVA, with time as the repeated measure, was performed.

^†Based on the general linear model with change in concentration as the dependent variable and adjusted for corresponding baseline value, total number of tablets consumed, husband’s occupation and possession of cultivable land. Serum ferritin was adjusted for elevated serum C-reactive protein and α₁-acid glycoprotein, by mathematical correction.

^‡P values based on log-transformed serum ferritin concentrations.