Assessment of Commercial Real-Time PCR Assays for Detection of Malaria Infection in a Non-Endemic Setting

Abstract

Malaria control and elimination require prompt diagnosis and accurate treatment. Conventional methods such as rapid diagnostic tests (RDTs) and microscopy lack the characteristics to detect low parasitemias, commonly found in asymptomatic parasitemias and/or submicroscopic malaria carriers. On the contrary, molecular methods have higher sensitivity and specificity. This study evaluated the performance of two commercial real-time polymerase chain reaction (PCR) assays, RealStar® Malaria PCR (RealStar-genus) and RealStar Malaria Screen&Type PCR (RealStar-species), compared with the reference Nested Multiplex Malaria PCR, for the detection of the main five Plasmodium species affecting humans. A total of 121 samples were evaluated. Values of sensitivity (98.9% and 97.8%) and specificity (100% and 96.7%) of the RealStar-genus and the RealStar-species assays, respectively, were very good. The limit of detection (LoD) for the RealStar-genus assay showed a mean value of 0.28 parasites/µL with Plasmodium falciparum samples; while, the LoD of the RealStar-species assay ranged from 0.09 parasites/µL for P. vivax to two parasites/µL for P. ovale. The time to complete a diagnosis was established in 4 hours. Our findings showed a very good concordance of both assays compared with the reference method, with a very good analytical sensitivity. RealStar-species assay was able to correctly characterize double and triple infections. Therefore, these RealStar assays have shown to be useful tools in malaria diagnosis in non-endemic countries and even endemic countries, and for malaria control in general, detecting low parasitemias with sensitivity similar to the most sensitive methods as nested PCR, but with lower time to get the results.

Diagnostic methods for Plasmodium knowlesi: performance, limitations and recommendations

“…RealStar Malaria PCR (RealStar-genus) and RealStar Malaria Screen & Type PCR (RealStar-species) which are genus-and species-specific, respectively, were also evaluated by Ramírez et al (2021) [48]. Out of 121 samples tested, RealStar-genus had a sensitivity of 98.9% with 1 P. ovale sample giving discordant results from the nested PCR method.…”

“…The method can be used to identify different Plasmodium species and determine the parasite density of the infection which is important for adequate treatment and disease management. The method is also less time-consuming with a turn-around time of approximately 2-4 hours when compared to the nested PCR assay which has a turn-around time of 6 hours [43,48].…”