Title : Age, sex, diagnostic modality, and seasonal patterns of malaria test positivity: Routine primary health care laboratory data from Gombe State, Nigeria
Abstract:
Introduction: Malaria test positivity rate (TPR) is a key surveillance indicator recommended by the World Health Organization to monitor transmission intensity. Subnational analyses using routine primary health care (PHC) laboratory data are limited in North-East Nigeria. This study assessed demographic, diagnostic, and seasonal determinants of malaria positivity using PHC laboratory records from Gombe State.
Methods: We conducted a retrospective analysis of 1,546 malaria tests performed between January and December 2025 at a PHC facility. TPR was calculated overall and stratified by age group (<5, 5–12, 13–17, 18–49, ≥50 years), sex, diagnostic modality (microscopy vs rapid diagnostic test [RDT]), and season (rainy: May–October; dry: November–April). Associations were evaluated using chi-square tests. Multivariable logistic regression estimated adjusted odds ratios (AORs) controlling simultaneously for age group, sex, diagnostic modality, and season.
Results: Malaria positivity differed significantly by age group, diagnostic modality, and season in crude analysis (p<0.001). Across diagnostic modalities, school-aged children (5–12 years) and adolescents (13–17 years) demonstrated the highest crude TPR, whereas adults showed lower positivity. Microscopy demonstrated higher TPR (54.5%) than RDT (37.1%). TPR was higher during the rainy season (46.0%) compared with the dry season (34.2%) (χ²=24.77, p<0.001).
In multivariable analysis, compared with adults aged 18–49 years, children aged 5–12 years (AOR=1.61; 95% CI: 1.21–2.16; p=0.001) and adolescents aged 13–17 years (AOR=2.19; 95% CI: 1.47–3.26; p<0.001) had significantly higher odds of malaria positivity. RDT was associated with lower odds of positivity compared with microscopy (AOR=0.48; 95% CI: 0.39–0.59; p<0.001). Sex and season were not independently associated after adjustment.
Conclusion: Routine PHC laboratory data revealed concentration of malaria positivity among school-aged children and adolescents, with substantial variation by diagnostic modality. Apparent seasonal differences were attenuated after adjustment, underscoring the importance of multivariable analysis when interpreting facility-based surveillance data.
Keywords: Malaria, Test positivity rate, Primary health care, Rapid diagnostic test, Microscopy and Age-related patterns
