Comparative Evaluation of Microscopy, Rapid Diagnostic Test (RDT), and PCR for Malaria Diagnosis among Clinical Malaria Patients in Gombe State, North-East Nigeria

Background: Malaria remains a major public health challenge in sub-Saharan Africa, with Plasmodium falciparum as the predominant species in West Africa. Accurate diagnosis is critical for effective case management and control. In Gombe State, Nigeria, microscopy, rapid diagnostic tests (RDTs), and polymerase chain reaction (PCR) are used with varying performance. This study assessed the diagnostic accuracy of a conventional HRP2-based RDT (cRDT) against microscopy confirmed by PCR.

Methods: A total of 427 patients aged 1–70 years, presenting with fever (≥37.5°C) or history of fever within the last 48 hours, were recruited. Written informed consent was obtained from all adult participants or guardians of minors. Demographic and clinical data were obtained through structured questionnaires, and venous blood samples were tested using microscopy, cRDT (SD Bioline Malaria Ag P.f), and PCR. Diagnostic performance metrics, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy, were calculated using microscopy/PCR as the reference. Agreement was assessed using Cohen’s kappa, and McNemar’s test evaluated systematic bias. Logistic regression identified predictors of microscopy-confirmed malaria.

Results: Microscopy detected malaria parasites in 75 participants (17.6%), all confirmed by PCR. The cRDT yielded 81.3% sensitivity, 67.3% specificity, 34.7% PPV, 94.4% NPV, and 69.8% overall accuracy. Agreement between cRDT and microscopy was moderate (κ = 0.42; 95% CI: 0.34–0.50), with a significant false-positive bias (McNemar’s χ² = 60.02, p < 0.001). Independent predictors of microscopy-confirmed malaria included male sex (OR = 1.85; 95% CI: 1.10–3.12), absence of bed net use (OR = 2.40; 95% CI: 1.35–4.26), and RDT positivity (OR = 5.67; 95% CI: 3.15–10.20).

Conclusion: The cRDT demonstrated good sensitivity and high NPV, supporting its utility for ruling out malaria in endemic areas. However, moderate specificity and low PPV highlight the need for confirmatory microscopy to reduce over-diagnosis. Strengthening diagnostic capacity, routine performance evaluations, and consistent bed net use should be prioritized in malaria control strategies for Gombe State.