G6PD Assessment Before Primaquine for Radical Treatment of Vivax Malaria

This will be a single-arm observational cohort study. Malaria patients with Plasmodium vivax and meeting study inclusion criteria, who give consent to be enrolled in the study, will have their G6PD status measured by the CareStart™ G6DP rapid diagnostic test (G6PD RDT), and primaquine prescribed according to the result. According to the G6PD RDT result, primaquine will be prescribed at 0.25mg/kg/day for 14 days (normal patients) or 0.75mg/kg weekly for eight weeks (deficient patients). All will receive treatment with chloroquine to clear asexual stages of infection. Patients will be reviewed at day 2, day 7 and day 14. At these visits patients will undergo a brief clinical assessment and a small blood sample will be taken for repeat haemoglobin measurement and dried blood spot for carboxyprimaquine measurement (day 7 and day 14 only). In general, antimalarial treatment will be unsupervised to reflect field conditions. However a subset of 25 G6PD normal patients at a single site will have each day of their primaquine treatment administered and observed at the treatment centre. This is to determine a calibration curve for primaquine pharmacokinetic studies. Dried blood spots will be stored appropriately. Day zero samples will be genotyped in Bangkok (MORU, Dr. Mallika Imwong) after DNA extraction. PCR-RFLP will be used to detect the allele associated with the Mediterranean variant of G6PD deficiency. In addition DNA extracts will be sent for more systematic genetic testing for known G6PD variants through existing collaborations with the Wellcome Trust Sanger Institute. The day 7 and 14 dried blood spot samples will be analysed in the MORU pharmacology laboratory for primaquine and carboxyprimaquine concentrations, from which adherence to primaquine can be determined retrospectively, using the subset of 25 patients receiving directly observed therapy to calibrate the results. Funder: WellcomeTrust, Grant reference: 107548/Z/15/Z