Performance of ParaHit and OptiMAL tests in the diagnosis of malaria in Mwanza, north-western Tanzania

Malaria rapid diagnostic tests (RDTs) are non microscopic tests that provide a rapid detection of malaria infections in infected individuals. The objective of this study was to evaluate the performance of ParaHit and OptiMAL tests for detection of malaria infections as compared with routine microscopy. This facility-based study was carried out in Mwanza, north-western Tanzania and involved outpatients attending Igoma Health Centre. Blood samples were tested for malaria infection using the two RDTs and compared with Giemsa stained blood films examined using microscope. A total of 243 individuals (median age= 22 years) were involved in the study. Microscopy had a higher detection rate of 19.7% (48/243) as compared to ParaHit (4.5%) and OptiMAL (3.7%). Low sensitivity of 21.2% and 17%, but high specificity of 99.4% for ParaHit and OptiMAL, respectively was observed. Of all positive blood slides for Plasmodium falciparum , 78.7% had low parasite density (80 -720 parasite/µl of blood). These slides were negative for malaria parasite for both RDTs. Over 80% of study participants who reported fever had negative blood slides for malaria parasites by microscopy. On the other hand, 44.7% of those who reported no fever had positive blood slides for P. falciparum. Study participants who reported to have fever and high parasite density above 720 parasite/µl were likely to be positive by both RDTs (OR= 6.8; P= 0.031529). In conclusion, the overall performance of both RDTs in detecting asexual P. falciparum was low as compared to microscopy and their performance were highly affected by parasite density. This calls for further evaluation studies before RDTs are widely used in peripheral health facilities in order to minimize potential severe consequences