Diagnostic accuracy of PfHRP2-based malaria rapid diagnostic tests and antigenemia persistence in Kenyan children from a holoendemic region: implications for case management and surveillance

Malaria remains a significant cause of childhood morbidity and mortality, with <i>Plasmodium falciparum</i> Histidine-Rich Protein 2 (<i>Pf</i>HRP2)-based malaria rapid diagnostic tests (mRDTs) widely used in endemic regions where microscopy is sometimes not feasible. While these tests offer high sensitivity, persistent <i>Pf</i>HRP2 antigenemia and gene deletions can cause false-positive and false-negative results, compromising their accuracy for malaria case management and surveillance. This study evaluated the diagnostic performance and antigen persistence of <i>Pf</i>HRP2-mRDTs using data from a longitudinal birth cohort of 750 children followed monthly from birth to 36 months in a holoendemic region of Kenya. Malaria diagnosis was performed using both microscopy and mRDTs, with a total of 15,006 clinical events recorded from 573 children between 2017 and 2023. Data from an independent acute febrile cohort of 937 children (<5 years) followed for 14 days was analyzed to validate the findings. The mRDT showed a high sensitivity of 97.27% but a moderate specificity of 65.00% in acute febrile illness, indicating frequent false-positive results. The positive predictive value was low (35.10%), suggesting that confirmatory testing is needed, while the negative predictive value was high (98.89%), reinforcing the reliability of mRDTs in ruling out malaria. Persistent <i>Pf</i>HRP2 antigenemia was observed, with a median antigen clearance time of 51.14 days, respectively. Higher initial parasite densities (>50,000/μL) were associated with a slower antigen decay rate (<i>p</i> = 0.001), highlighting the challenge of interpreting positive mRDT results after treatment. Validation using the acute febrile cohort showed that mRDT specificity exceeded 95% at initial diagnosis and follow-up. Overall, <i>Pf</i>HRP2-based mRDTs remain valuable for frontline malaria diagnosis but are limited by antigen persistence, leading to false positives in follow-up testing. Where feasible, integration of confirmatory diagnostic methods, such as microscopy or molecular assays, could improve the performance of malaria case management and clinical decision making, particularly in high-transmission settings.