Performance and Comparative Evaluation of a Novel Diagnostic Assay, Novaplex™ Malaria Assay, against Routine Diagnostic Techniques in the Detection of Different Plasmodium spp. in Kenya

Author(s): Lewis Karani, Kelvin Thiong’o, Maureen Otinga, Mary Ombati, Maureen Osano, Lynette Wangechi, Nemrod Gesusu, Eva-Aluvaala Nambati, Noah M. Onchieku, Francis Kimani

Background: Accurate and rapid diagnosis of malaria is crucial for effective treatment and control. More so, accurate species identification is central in guiding treatment strategies across infections with different species of Plasmodium. This study aimed to evaluate the performance of a novel malaria diagnostic kit, NovaplexTM Malaria Assay, compared to routine diagnostic techniques currently in use, including microscopy, rapid diagnostic tests (RDTs), and polymerase chain reaction (PCR) in malaria diagnosis. Methods: A total of 142 suspected malaria cases from Matayos, a malaria endemic zone in Kenya, were sampled. Whole blood samples were collected, Plasmodium parasite positivity and species identification were performed using microscopy, rapid diagnostic kits, the NovaplexTM malaria diagnostic assay, and qPCR. Sensitivity, specificity, positive predictive value [PPV], negative predictive value [NPV], accuracy, and agreement [Cohen’s kappa] were calculated to assess the diagnostic performance of the NovaplexTM kit against the rest of the techniques. Results: Our analyses demonstrated that the NovaplexTM malaria assay yields a superior outcome compared to microscopy or mRDTs in terms of sensitivity, accuracy and NPV. The assay showed an overall diagnostic agreement with qPCR. Also, the kit showed an almost similar performance to qPCR in species identification. Using qPCR as the comparator “gold standard” test for the analysis, the sensitivity and specificity of the NovaplexTM assay was 94.8% and 100% respectively, while the sensitivity of microscopy and RDT was 63.7% and 61.5% respectively. The positive and negative predictive values were 100% and 53.9% respectively, for the NovaplexTM assay. This was in contrast to NPV values for microscopy and RDT which were 12.5% and 11.9% respectively. The accuracy of the NovaplexTM assay was recorded at 95.8% having a substantial agreement with qPCR at k=0.679 (95% CI: 0.442 to 0.917). The level of accuracy for Microscopy and RDT was determined to be 65.5% and 63.4% respectively, with a slight agreement with qPCR at k=0.148 (95% CI: 0.047 to 0.248), and k=0.136(95% CI: 0.042 to 0.230) respectively. Conclusion: These findings demonstrate that the Novaplex assay outperformed microscopy or RDTs, showing comparable performance to qPCR in the identification and speciation of Plasmodium species in malaria infections. The high sensitivity, specificity, and overall agreement highlight the potential of the Novaplex assay as a reliable diagnostic tool for malaria. Implementation of this assay in routine clinical practice could improve the accuracy and efficiency of malaria diagnosis, leading to timely and appropriate treatment, enhanced surveillance, and effective control measures. Further validation studies and field evaluations are warranted to confirm the feasibility and cost effectiveness of this diagnostic assay in diverse malaria-endemic low resource settings.