Roschnik 2004 (C).

Methods	Cluster‐randomised trial. 2‐arm design with randomisation at school level.
Participants	1785 children (1510 followed up), both sexes (747 females (49.5%), aged 7–12 years. The study included 51 primary schools: 20 in Iloilo and 31 in Guimaras, Philippines. Baseline prevalence of anaemia: ˜15%. Socioeconomic status not reported.
Interventions	Schools were randomly allocated to one of the following treatments: Group 1 (25 schools, unclear the number of children randomised): children received 108 mg of elemental iron (as 325 mg ferrous sulphate); Group 2 (26 schools, unclear the number of children randomised): children received no intervention. Length of the intervention: 10 weeks
Outcomes	Anaemia, haemoglobin, haemoglobin change.
Notes	Supplementation started between 1 and 7 weeks after the baseline survey and the second survey took place between 5 and 18 weeks after the end of the iron supplementation. The consumption of each tablet was recorded by the teachers. Side effects were not recorded. All 10 iron tablets were taken by 93.4% of children. 67% of children were infected with one or more intestinal worms. Malaria endemicity not reported. Authors provided the ICC (0.1123) and design effect (4.35) to adjust data by the effect of clustering; the estimated effective sample size was used in the analyses.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	All 51 schools were assigned to two groups using a random number table.
Allocation concealment (selection bias)	Low risk	Not reported. Since the intervention was allocated at school level, it is unlikely there was a selection bias at the individual level.
Blinding (performance bias and detection bias) All outcomes	High risk	Participants: not reported. Personnel: not reported Outcome assessors: not reported.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	15.4% of attrition. Losses presumably higher among the control group as two schools were dropped out because they were unable to collect the baseline measurements within the month allotted.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	High risk	The second blood sample was withdrawn between 5 and 18 weeks after the end of the iron supplementation. Fourteen of the 49 schools in the study had participated for about 2 months in the fortified rice programme: six in the intervention group and eight in the control group. The mean haemoglobin concentration of children in the 14 schools that had participated in the programme was slightly but significantly higher than that of children in the other 25 schools (126.4 g/L versus 125.0 g/L, P ¼ 0.031). Analysis was not adjusted by the effect of clustering in data.