Patients were recruited on presentation to the ward. All children in the right age group who presented to the ward had their haematocrit and blood film done by a project field worker. Children with a PCV of less than 21% were offered assessment by a project doctor. If assessment was permitted, and the patient fulfilled the entry criteria, then written consent was sought from the parent/guardian. The study was explained in the parent's/ guardian's preferred language, and written informed consent was obtained on approved forms.