Field and laboratory evaluation of Abbott-Bioline™ Malaria Ag Pf/Pv RDT performance in a high-transmission setting: contrasting results with a low-endemic area.

BACKGROUND

Recent reports documented catastrophic sensitivity failures (18%) of Abbott-Bioline™ Malaria Ag Pf/Pv rapid diagnostic tests (RDTs) at the Thailand-Myanmar border, prompting WHO to issue an information notice on quality concerns. We evaluated the same RDT lots under controlled laboratory conditions and in a high-transmission field setting in Madagascar to assess whether performance varied across epidemiological contexts.

METHODS

Laboratory evaluation tested four Abbott-Bioline™ Malaria Ag Pf/Pv lots (05DDI018BH, 05DDI020BA, 05DDI041AB, 05DDI040AA) using serial dilutions of cultured Plasmodium falciparum (0-60,784 parasites/µL). Field evaluation enrolled 218 consecutive febrile patients at Ranomafana health centre, southeastern Madagascar. Performance of both RDTs (Abbott-Bioline™ Malaria Ag Pf/Pv and Parascreen® Malaria Ag Pf/Pan) was assessed against microscopy and real-time PCR as reference standards.

RESULTS

In laboratory testing, substantial inter-lot variability was observed, with detection failures occurring between 97 and 373 parasites/µL. Incomplete blood migration and faint test lines were noted at lower densities. In the field, malaria prevalence was 70.2% by PCR and 48.6% by microscopy. Against microscopy, Abbott-Bioline™ Malaria Ag Pf/Pv achieved sensitivity of 99.1% (95% CI 94.9-100) and specificity of 93.7% (95% CI 87.4-97.4). Parascreen® Malaria Ag Pf/Pan showed sensitivity of 100% (95% CI 96.6-100) and specificity of 92.8% (95% CI 86.3-96.8). Against PCR, sensitivity decreased to 73.2% for Abbott-Bioline™ Malaria Ag Pf/Pv and 74.5% for Parascreen® Malaria Ag Pf/Pan, while specificity remained 98.5% for both tests. No significant difference was observed between RDTs (p > 0.05).

CONCLUSIONS

Despite using identical lots that showed 18% sensitivity at the Thailand-Myanmar border, Abbott-Bioline™ Malaria Ag Pf/Pv RDTs achieved 99.1% sensitivity in Madagascar. This difference likely reflects higher parasite densities in the Malagasy high-transmission setting (geometric mean 10,006 parasites/µL) compared to low-transmission elimination contexts. Both RDTs met WHO performance thresholds against microscopy but missed approximately 25% of PCR-positive infections. These findings demonstrate that RDT performance is highly context-dependent and underscore the need for enhanced post-deployment surveillance.