Misidentification of Plasmodium mixed-infections leads to an overestimation of falciparum malaria

Despite the fact that malaria elimination is nearing in several countries, we continue to struggle with accurate diagnosis and thus treatment. The purpose of this study was to determine the rate of Plasmodium species misidentification (MI) by microscopy (MS). The study was based on previously published reports in which MS-PCR pairs were analysed to identify Plasmodium misidentification rates (by MS). Region- and species-wise misidentification rates were also estimated. A total of 2706 MS-PCR pairs were extracted from 16 different locations across 11 Indian states. MS-PCR pair analysis revealed 15% misidentification rate (408/2706). Surprisingly, microscopy misidentified more than 98% of mixed infections (400/405) as mono-infections (almost all as P. falciparum mono infections). The study identifies Jharkhand and Madhya Pradesh as major contributors (>20%) to Plasmodium species misidentification by microscopy. These findings suggest that we are overestimating P. falciparum burden, potentially wasting elimination resources, and underestimating non-falciparum species. The study also addresses an important issue concerning analysis of misidentification & sub-microscopic infection data (SMI). The proposed analysis (for MI and SMI) will aid in deciphering MI and SMI data in a more granular manner, generating actionable data for elimination programmes in various countries.