Kvalsvig 1991a

Methods	RCT Length of follow‐up: 1 month
Participants	Infected children identified by screening Number analysed for primary outcome: unclear Age range: unclear Inclusion criteria: most severely infected 100 children in a primary school Exclusion criteria: children with schistosomiasis
Interventions	Single dose vs placebo Mebendazole: 500 mg; Placebo.
Outcomes	Cognition tests: card sorting task (coloured cards; cancellation task ‐ striking out of letter 's' in text, number done in a period) Not included in review: height; weight at baseline; standardized using NCHS standards; stool examination (intensity index designed for this trial); no nutritional outcomes reported that can be used in the review
Notes	Location: South Africa Community category: 1 No data used in meta‐analysis since SDs not provided. Source of funding: Janssen Pharmaceutica, South African Medical Research Council.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"Assigned randomly", no further details provided.
Allocation concealment (selection bias)	Unclear risk	No details reported.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	"A 'blind' procedure was adopted; the research assistant did not know whether a particular child had received drug or placebo". No further details provided.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No details reported. Inclusion of all randomized participants (number evaluable/number randomized): unclear.
Selective reporting (reporting bias)	Low risk	All stated outcomes reported.
Other bias	Low risk	No obvious other source of bias.