Rapid Malaria Tests Assessed After Artemisinin Therapy

falciparum infection from residual antigens from a previous infection is crucial in endemic areas where residents are repeatedly exposed to malaria.

Scientists at Karolinska Institute (Stockholm, Sweden) studied 53 Tanzanian children less than five years of age with uncomplicated P. falciparum malaria infections. The children were followed up on nine occasions after initiation of artemether-lumefantrine treatment. At each visit capillary blood samples was collected for the histidine-rich protein 2 (HRP2 and lactate dehydrogenase (LDH)-based RDTs, Giemsa and acridine orange-stained blood smears for microscopy and real-time polymerase chain reaction (PCR).

The two RDTs used were the ParaHITf (Span Diagnostics Ltd.; Surat, India) that detects P. falciparum-specific HRP2 antigen and the CareStart Malaria assay (AccessBio; Somerset, NJ, USA) that detects P. falciparum-specific LDH antigen and were performed and interpreted on site. PCR genotyping was performed to distinguish reinfections from recrudescence. Assessment of clearance times and detection of recurrent P. falciparum infections were done for all diagnostic methods.

The median clearance times were 28 (range 7 to greater than 42) and 7 (2 to 14) days for HRP2 and LDH-based RDTs, 2 (1 to 7) and 2 (1 to 14) days for Giemsa and acridine orange-stained blood smear and 2 (1 to 28) days for real-time PCR. RDT specificity against Giemsa-stained blood smear microscopy was 21% for HRP2 on day 14, reaching 87% on day 42, and equal to or greater than 96% from day 14 to 42 for LDH. There was no significant correlation between parasite density at enrolment and duration of HRP2 positivity. Recurrent malaria infections occurred in 10 children and the HRP2 did not detect eight recurrent infections and LDH-based RDTs did not detect two.

The authors concluded that the LDH-based RDT was superior to HRP2-based for monitoring of treatment outcome and detection of recurrent infections after ACT in this moderately high transmission setting. The results may have implications for the choice of RDT devices in similar transmission settings for improved malaria case management. The study was published on October 1, 2013, in the Malaria Journal.

Related Links:
Karolinska Institute
Span Diagnostics Ltd.
Access Bio Inc.