Agarwal 2003 (C).

Study characteristics
Methods	Design: 3‐arm, cluster‐randomised trial Unit of randomisation: class; "As school teachers did not agree to randomization at the individual girl level, the randomization was done at the class section level for the 60 class sections (all class sections taken)" (quote)
Participants	Setting/location: 4 government senior secondary schools (all of these schools cater to the middle socioeconomic group population) in North‐East Delhi, India Sample size: 2088 girls Age range: 10‐17 years Baseline prevalence of anaemia: ~ 48% Inclusion criteria: secondary school girls aged 10‐17 years old Exclusion criteria: girls with haemoglobin < 7.0 g/dL
Interventions	Intervention: 60 class sections were allocated to 1 of 3 groups. Group 1 (n = 691): participants did not receive any tablets for the first 100 days and haemoglobin was estimated at 115 (± 5) days. They were thereafter given tablets containing 100 mg of elemental iron and 500 μg (0.5 mg) of folic acid with advice to take 1 tablet daily for 100 days; blister packs were distributed once a week (as in group 2). Group 2 (n = 702): participants received same tablet, containing 100 mg of elemental iron and 500 μg (0.5 mg) of folic acid, one every day for 100 days; blister packs were provided once a week. Group 3 (n = 695): participants received same tablet weekly until group 1 completed the study (230 days). Length of the intervention: 100 days (we did not consider the second period in which group 1 and 3 received supplementation)
Outcomes	Anaemia (haemoglobin < 120 g/L) Haemoglobin Ferritin
Notes	Comments: The intervention was supervised. Compliance was monitored verbally on weekly visits when 7 tablets in a blister pack were distributed. The used blisters were collected each week; results were not reported. Sexual maturity rating was done using Tanner’s criteria. The time of menarche and regularity of menstrual periods were noted. We adjusted the results of this study to account for the effect of clustering in the data; we used the estimated effective sample size in the analyses.  Malaria endemicity was not reported. Study start date: August 1996 Study end date: February 1999 Funding source: UNICEF, Delhi Conflicts of interest: Not available
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Comment: randomisation was done at the class section level for 60 class sections. Method of sequence generation not described
Allocation concealment (selection bias)	Low risk	Comment: not mentioned; however, since randomisation was performed at class section level, selection bias at individual level was unlikely
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Comment: not described for participants, personnel nor outcome assessors; however, seems unlikely to have been blinded, and no placebo was used
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: 7 girls in the daily administered group during the second week of intervention complained of gastric side effects and requested not to continue in the study and were excluded
Selective reporting (reporting bias)	High risk	Comment: girls with haemoglobin < 70 g/L (0.3%) were eliminated from the analysis. Plasma ferritin and C‐reactive proteins (CRP) were estimated in every tenth girl of the study groups; it is unclear how each girl was selected for these analyses. Data not available for the second measurement
Other bias	Low risk	Comment: appears to be free of other bias