Malaria Test Positivity by Light Microscopy and an HRP2-Based Rapid Diagnostic Test among Children Attending a Primary Health-Care Facility in Omoku, Rivers State, Nigeria: A Cross-sectional Study

Abstract

Background: Accurate parasitological diagnosis is central to malaria case management. This study described malaria positivity detected by light microscopy and a histidine-rich protein 2 (HRP2) rapid diagnostic test (RDT) among children attending a primary health-care facility in Omoku, Rivers State, Nigeria. Methods: A facility-based cross-sectional study included 82 children aged 1–17 years. Venous blood was examined using Giemsa-stained thick and thin films and the STANDARD Q Malaria P.f Ag Test. Method-specific positivity and microscopy-defined age-specific positivity were summarized using counts, percentages, and Wilson 95% confidence intervals (CIs). Results: Microscopy detected malaria parasites in 10 of 82 participants (12.2%; 95% CI, 6.8%–21.0%), whereas the RDT was positive in 7 of 82 participants (8.5%; 95% CI, 4.2%–16.6%). Thus, the microscopy positivity estimate was 3.7 percentage points higher. All microscopy-positive infections were identified as Plasmodium falciparum. Among the 10 microscopy-positive specimens, 5 had low parasite density (1–999 parasites/µL) and 5 had intermediate density (1,000–9,999 parasites/µL); none was classified in the high-density category (≥10,000 parasites/µL). Microscopy positivity was similar across age groups, although estimates were imprecise because of the small number of positive cases. Conclusion: Microscopy yielded a higher positivity estimate than the HRP2-based RDT in this facility sample. The absence of a participant-level cross-tabulation of paired test results precluded calculation of agreement, sensitivity, specificity, and predictive values; therefore, the findings do not establish diagnostic superiority or interchangeability. Larger, prospectively designed studies with quality-controlled microscopy, complete paired results, and molecular resolution of discordant specimens are required.