A proposed method of grading malaria chemoprevention efficacy

Abstract

The efficacy and effectiveness of antimalarial drugs are threatened by increasing levels of resistance and therefore require continuous monitoring. Chemoprevention is increasingly deployed as a malaria control measure, but there are no generally accepted methods of assessment. We propose a simple method of grading the parasitological response to chemoprevention (focusing on seasonal malaria chemoprevention) that is based on pharmacometric assessment.

Figure 1.

The proposed Mahidol Oxford Tropical Medicine Research Unit (MORU) grading of malaria chemoprevention effectiveness has six levels ranging from fully effective (M1) to completely ineffective (M6). Asexual malaria parasites, if present, should be cleared by the SMC dose and reinfections suppressed for at least 28 days. The proportion of subjects who test qPCR positive for Plasmodium falciparum at day 28 in filter paper samples provides the primary effectiveness measure. At higher levels of SMC failure (≥M3), gametocytaemia is detectable by thick blood film microscopy and the infection is therefore likely transmissible. Initially all breakthrough infections are newly acquired but with very high levels of failure (≥M5), some infections detected at day 28 are recrudescences.