Xmn I digest of DHFR F-M4 amplicon from saliva, urine and blood samples of patients 7, 15, 17 and 28. Qs, Qu denotes saliva and urine samples extracted by Qiagen® kit (crude cell lysate protocol). Blood samples were extracted on different days by Chelex from dry filter paper blots. U is undigested DHFR F-M4 amplicon. Identical restriction fragment patterns are evident on different extracts from each patient. Patients 7, 15 and 28 were infected with parasites carrying the mutated (antifolate resistance associated) allele (coding for DHFR Arg-59). Patient 17 carried mixed wild type (Cys-59) and mutated (Arg-59) variants, of which the mutated form was barely discernible in the urine amplicon. Incomplete digestion is present in some amplications, with a band at 326 bp.