Detection and identification of plasmodium species causing malaria in Malawi using rapid diagnostic tests

Malaria represents one of the oldest documented diseases among humans and even today organisms in the genus Plasmodium kill more people than any other infectious disease, especially in tropical and subtropical areas. The four most common species which infect humans are Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale and Plasmodium malaria. Of these four species, Plasmodium falciparum and Plasmodium vivax account for 95 percent of infections globally. Microscopy has been used since early days for the diagnosis of malaria because this method is simple, does not require highly equipped facilities, and in most cases enables differentiation among the species causing malaria in humans when performed by skilled microscopy readers. However, this method has been misleading in identifying parasite species, especially in the case of low level parasitemia, a mixed parasite infection, or modification by drug treatment as well as in placental malaria. Malaria rapid diagnostic tests (RDT) have played a major role in malaria management; particularly in providing blood based diagnosis in remote locations where microscopy based diagnosis is unavailable. These diagnostic tests are fast and easy to perform and do not require electricity or specific equipment. As part of strengthening malaria diagnostics in Malawi, the Ministry of Health and Population strongly recommends the use of malaria RDT’s at all levels of the health care delivery system. However, malaria microscopy remains a gold standard test for malaria. All patients (regardless of age) with suspected uncomplicated malaria should have a confirmed diagnosis with malaria RDT before anti-malaria treatment is administered. Based on field performance evaluations that assessed performance, quality control and production capacities of the manufacturing companies of malaria RDT’s, the Ministry of Health and Population recommended two brands of Histidine Rich Protein 2 (HRP-2), RDT’s for use in Malawi. These are SD Bioline malaria Ag Pf and the New Paracheck malaria Ag Pf. All these RDT’s are able to detect only P. falciparum. However, other species have been reported to exist in the country and there is a need to find proper RDT’s which will be able to detect all other species including P. falciparum. The main aim of this study was to evaluate Paramax-3 Pf/Pv/Pan RDT (Zephyr Biomedicals, India), if used in Malawi, could be able to detect and identify the different species of Plasmodium causing malaria in Malawi. The study recruited a total of 250 adult and infants at Bwaila Hospital in Lilongwe, Malawi. Study results showed that the overall sensitivity and specificity of the Paramax-3 RDT used in the study were 100 percent and 83 percent respectively. However, it was observed that the RDT test was not able to identify the P. ovale, and in some cases, the RDT test was positive for P. falciparum when the PCR identified the species as P. ovale. No P. vivax was detected both by RDT and PCR. This study was able to detect and identify the presence of P. malaria and P. ovale in Malawi apart from the P. falciparum. There were no significant differences between microscopy results compared to both the RDT and the PCR, with 94 percent and 98 percent sensitivities of R1 and R2 compared to RDT, as well as 94 percent and 96 percent sensitivities for R1 and R2 compared to PCR respectively. Both R1 and R2 had low specificities for example, R1 had 72 percent and R2 had 80 percent compared to RDT. Comparing R1 and R2 to PCR, the sensitivities were 64.9 percent and 67.2 percent respectively. However, the readers had difficulties differentiating the different species microscopically. The history of anti-malaria treatment had no significant effect on the outcome of the results in both the RDT and PCR