Comparative analysis of diagnostic methods used for assessing incidence of malaria in two regions from South India

Background: Malaria is a vector-borne disease of major public health concern in several tropical and subtropical countries. Five different Plasmodium species are known to cause malaria. For optimal public health measures, region-specific prevalence of Plasmodium species should be identified by optimal diagnostic methods available. In this study, we have detected the malaria incidence rates in two regions of South India and compared the merit of three different diagnostic methods available for detection of malaria. Materials and Methods: Six hundred blood samples from febrile symptomatic patients were screened for malaria from Bengaluru and Vijayapura regions of Karnataka, India, by microscopy, rapid diagnostic test (RDT), and nested polymerase chain reaction (PCR) methods. Results: The incidence rate of malaria in Vijayapura and Bengaluru was 8.6% (26/300) and 7% (21/300), respectively. The rate of malaria infection by Plasmodium vivax was higher in Bengaluru (80.9%) compared to Vijayapura (69%), whereas the rate of Plasmodium falciparum infection was higher in Vijayapura (23%) compared to Bengaluru (14.2%). The mixed infection rate was slightly higher from Vijayapura region. One isolate detected as P. falciparum by microscopy and RDT method was identified as mixed infection by PCR. Three and two isolates which were negative by microscopy and RDT methods, respectively, tested positive by PCR, whereas eight isolates identified as P. vivax by RDT method were negative by PCR and microscopy methods. The sensitivity and specificity of microscopy-based detection method were 93% and 100%, respectively, whereas the sensitivity and specificity of RDT method were observed to be 95% and 75%, respectively. Detection of Plasmodium species by PCR was highly sensitive and specific compared to microscopy or RDT method. Conclusion: The incidence of malaria infection in these regions is moderate. Malaria infection in these regions was caused predominantly by P. vivax. Accuracy of the malaria detection was superior by PCR method compared to conventional methods tested.