Table 3

Comparison of iron supplementation effects across schedule, duration and dosing schemes

Haemoglobin (g/L)*Ferritin (ng/mL)*Anaemia†Iron deficiency†Iron deficiency anaemia†
Weekly frequency
 Frequent (3–7 times/week)
  n13288574424
  Estimate6.620.90.620.310.20
  95% CI(5.6 to 7.6)(18.2 to 23.7)(0.56 to 0.69)(0.24 to 0.38)(0.13 to 0.32)
 Intermittent (1–2 times/week)
  n32181043
  Estimate4.86.70.610.240.22
  95% CI(3.4 to 6.2)(3.7 to 9.6)(0.41 to 0.92)(0.09 to 0.66)(0.06 to 0.77)
 P value for interaction0.14<0.0010.870.730.91
Duration
 1–3 months
  n965927186
  Estimate7.313.90.530.380.23
  95% CI(6.0 to 8.6)(11.7 to 16.1)(0.45 to 0.62)(0.25 to 0.57)(0.07 to 0.81)
 4–6 months
  n5341342619
  Estimate5.725.10.630.210.15
  95% CI(4.3 to 7.0)(20.0 to 30.1)(0.54 to 0.72)(0.15 to 0.30)(0.11 to 0.22)
 ≥7 months
  n187842
  Estimate2.611.80.840.840.86
  95% CI(1.4 to 3.8)(5.9 to 17.7)(0.69 to 1.03)(0.67 to 1.06)(0.63 to 1.18)
 P value for interaction0.010.010.070.05<0.001
Dose
 Low (1st tertile for age)
  n5941271713
  Estimate4.413.70.680.330.26
  95% CI(3.2 to 5.6)(9.5 to 17.9)(0.57 to 0.81)(0.22 to 0.50)(0.17 to 0.41)
 Moderate (2nd tertile for age)
  n3222231710
  Estimate8.626.00.550.270.08
  95% CI(5.9 to 11.4)(19.0 to 32.9)(0.47 to 0.66)(0.18 to 0.40)(0.05 to 0.14)
 High (3rd tertile for age)
  n3725992
  Estimate7.216.20.640.240.08
  95% CI(5.3 to 9.1)(13.4 to 19.0)(0.49 to 0.84)(0.12 to 0.47)(0.01 to 0.69)
 P value for interaction0.0040.0080.440.820.02
  • *Weighted mean difference.

  • †Pooled risk ratio.

  • ‡Trials of short duration were more likely to have a higher proportion of patients with anaemia. No significant associations were observed between duration and haemoglobin, anaemia, iron deficiency and iron deficiency anaemia outcomes after controlling for baseline anaemia. After control for anaemia, an increase in serum ferritin was associated with trials of longer duration (see online supplemental appendix 5).