Methodological issues in the assessment of antimalarial drug treatment: analysis of 13 studies in eight African countries from 2001 to 2004

Abstract

The objectives of these analyses were to assess the feasibility of the latest WHO recommendations (28-day follow-up with PCR genotyping) for the assessment of antimalarial drug efficacy in vivo and to examine how different statistical approaches affect results. We used individual-patient data from 13 studies of uncomplicated pediatric falciparum malaria conducted in sub-Saharan Africa, using chloroquine (CQ), sulfadoxine/pyrimethamine (SP), or amodiaquine (AQ). We assessed the use effectiveness and test performance of PCR genotyping in distinguishing recurrent infections. In analyzing data, we compared (i) the risk of failure on target days (days 14 and 28) by using Kaplan-Meier and per-protocol evaluable patient analyses, (ii) PCR-corrected results allowing (method 1) or excluding (method 2) new infections, (iii) and day 14 versus day 28 results. Of the 2,576 patients treated, 2,287 (89%) were evaluable on day 28. Of the 695 recurrences occurring post-day 14, 650 could be processed and 584 were resolved (PCR use effectiveness, 84%; test performance, 90%). The risks of failure on day 28 with Kaplan-Meier and evaluable-patient analyses tended to be generally close (except in smaller studies) because the numbers of dropouts were minimal, but attrition rates on day 28 were higher with the latter method. Method 2 yielded higher risks of failure than method 1. Extending observation to 28 days produced higher estimated risks of failure for SP and AQ but not for CQ (high failure rates by day 14). Results support the implementation of the current WHO protocol and favor analyzing PCR-corrected outcomes by Kaplan-Meier analysis (which allows for dropouts) and retaining new infections (which minimizes losses).

FIG. 1.

Comparison of Kaplan-Meier and evaluability (per-protocol) analyses (failure rates on day 28) using method 1 (PCR corrected, with cases unresolved by PCR excluded) (open symbols) and method 2 (PCR corrected, with cases unresolved by PCR and new infections both excluded) (closed symbols) by drug treatment.

FIG. 2.

Failure rates (95% CIs) on day 14 (crude) (white bars) and day 28 (PCR corrected, method 1) (gray bars) for chloroquine, sulfadoxine-pyrimethamine, and amodiaquine.