Table 1.
Characteristics of studies included in meta-analysis of randomised iron supplementation trials for child health
| Study characteristics | |
| Eligible publications, n | 142 |
| Unique trials, n | 129 |
| Trial arms randomised to iron, n | 201 |
| Trial arms randomised to placebo or control, n | 177 |
| Individuals randomised to iron, n | 18 142 |
| Individuals randomised to placebo or control, n | 16 422 |
| WHO region, n (%)* | |
| Africa | 40 (19.9) |
| Americas | 36 (17.9) |
| Eastern Mediterranean | 12 (6.0) |
| Europe | 26 (12.9) |
| South-East Asia | 67 (33.3) |
| Western Pacific | 20 (10.0) |
| Decade of publication, n (%)† | |
| 1970–1979 | 3 (2.1) |
| 1980–1989 | 17 (12.0) |
| 1990–1999 | 26 (18.3) |
| 2000–2009 | 69 (48.6) |
| 2010–2017 | 27 (19.0) |
| Population characteristics | |
| Age, n (%)* | |
| 0–5 months | 45 (22.4) |
| 6–23 months | 44 (21.9) |
| 2 to <5 years | 37 (18.4) |
| 5 to <12 years | 50 (24.9) |
| ≥12 years | 25 (12.4) |
| Per cent female, median (IQR)* | 50.4 (47.0, 55.2) |
| All female, n (%) | 28 (13.9) |
| All male, n (%) | 6 (3.0) |
| Mixed male and female, n (%) | 125 (61.2) |
| Missing baseline sex data, n (%) | 42 (20.9) |
| Baseline per cent anaemic, median (IQR)* | 55.2 (9.1, 100.0) |
| All anaemic, n (%) | 36 (17.9) |
| All non-anaemic, n (%) | 32 (15.9) |
| Mixed anaemic and non-anaemic, n (%) | 70 (34.8) |
| Missing baseline anaemia data, n (%) | 63 (31.3) |
| Intervention characteristics | |
| Frequency, n (%)* | |
| 1–2 days/week | 35 (17.4) |
| 3–7 days/week | 163 (81.1) |
| Missing frequency data | 3 (1.5) |
| Duration, n (%)* | |
| 1–3 months | 113 (56.2) |
| 4–6 months | 62 (30.9) |
| ≥7 months | 26 (12.9) |
| Weekly iron dose (mg) by child age category, median (IQR)* | |
| 0–5 months | 52.5 (49.0, 70.0) |
| 6–23 months | 70.0 (47.5, 162.8) |
| 24–59 months | 105.0 (60.0, 210.0) |
| 5–11 years | 265.1 (120.0, 403.1) |
| 12–19 years | 205.0 (85.0, 325.0) |
| Missing dose information, n | 28 |
| Formulation, n (%)* | |
| Ferrous sulfate | 122 (60.7) |
| Ferrous fumarate | 20 (10.0) |
| Other or unspecified | 59 (27.7) |
| Factorial trials, n (%)‡ | 30 (23.3) |
| Zinc, n (%)§ | 11 (36.7) |
| Vitamin A, n (%)§ | 6 (20.0) |
| Other, n (%)§ | 13 (43.3) |
*Denominator is the number of unique groups randomised to iron (n=201).
†Denominator is the number of publications (n=142).
‡Denominator is the number of unique trials (n=129).
§Denominator is the number of factorial trials (n=30).