Verhoef 2002.

Methods	Double‐blind, placebo‐controlled trial. 2x2 factorial design with randomisation at individual level.
Participants	328 children, both sexes (148 females (45%)), aged 2–36 months. The study was done during rainy seasons in the period 1998–2000 in Mtito Andei Division, Eastern Province, Kenya. Children were randomly sampled. At screening, children were judged eligible for the study when they met the following criteria: the haemoglobin concentration was 60–110 g/L (anaemic); the axillary temperature was below 37·5C; there were no symptoms suggestive of malaria or anaemia, or any systemic illness occurring in combination with a blood dipstick test result indicating current or recent malarial infection; the parents intended to stay in the study area during the intervention period and gave their consent; no allergy to sulfa drugs was reported; and no sulfa drugs had been used in the previous 3 weeks. Children with a positive malaria dipstick test result but without symptoms of systemic illness were included.
Interventions	Participants were randomly assigned to one of four groups Group 1 (n = 82): children received intermittently sulphadoxine‐pyrimethamine and iron supplement of 6 mg elemental iron (as ferrous fumarate) per kg body weight weekly (approximately 65 mg of elemental iron per week); Group 2 (n = 82): children received intermittently sulphadoxine‐pyrimethamine and iron placebo; Group 3 (n = 82): children received intermittently sulphadoxine‐pyrimethamine placebo and iron supplement of 6 mg elemental iron (as ferrous fumarate) per kg body weight weekly (approximately 65 mg of elemental iron per week); Group 4 (n = 82): children received intermittently sulphadoxine‐pyrimethamine placebo and iron placebo. Iron was administered twice per week as ferrous fumarate in a suspension at a target dose of Length of the intervention: 12 weeks For the purposes of this review, groups 1 and 3 were combined (iron) and compared with the combination of groups 2 and 4 (no iron).
Outcomes	Malaria attacks, adverse drug reactions, anaemia, iron deficiency, serum ferritin (could not be extracted) and difference in mean haemoglobin change from that of placebo (we calculated final haemoglobin concentrations).
Notes	Sulphadoxine‐pyrimethamine was administered by the clinical officer employed by the project once every 4 weeks at therapeutic doses. Iron was administered by community health‐workers. Children in all groups were under intense health surveillance throughout the intervention period. Malaria transmission is highly seasonal in this area
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Balanced block randomisation (41 blocks). The allocation schedule was generated by one of the researchers for each block, by means of tables with randomised permutations, and only after acceptance of all children making up a block.
Allocation concealment (selection bias)	Low risk	The order of the children listed in each block was concealed from the person generating the allocation schedule. Both placebos and active compounds were administered as suspensions that were indistinguishable in taste and appearance. Bottles were colour‐coded, but none of the field investigators was aware of the code until after crude analysis and a plan for further analysis had been prepared.
Blinding (performance bias and detection bias) All outcomes	Low risk	See above.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Of 328 children undergoing randomisation, 307 (94%) completed the trial and 21 (6%) did not (migrated or moved temporarily from the study area, 13; parents withdrew consent, three; developed severe anaemia, one; died, one; developed malaria but treated elsewhere, one; unknown reasons, two). Balanced losses to follow‐up.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Low risk	The study appears to be free of other sources of bias.