# False-positive Malaria Rapid Diagnostic Tests are Prevalent Among Children Under 5 Years of Age in Uganda

## TL;DR

False malaria test results are common in young children in Uganda, leading to overestimation of malaria cases and potential misuse of antimalarial drugs.

## Contribution

This study quantifies the prevalence of false-positive malaria rapid diagnostic tests in children under 5 in Uganda and identifies predictive factors.

## Key findings

- False-positive mRDTs occurred in 10.7% of children under 5 with negative microscopy results.
- False-positive results were higher in children with recent fever, antimalarial use, or anemia.
- A model combining clinical and environmental variables predicted false positives better than individual models.

## Abstract

Malaria rapid diagnostic tests (mRDTs) are a cornerstone of malaria testing and treatment efforts globally. However, positive mRDT results can occur after treatment due to antigen persistence, even in the absence of malaria parasites. False-negative mRDTs are well-described, but less is known about the prevalence and consequences of such false-positive results.

We estimated the prevalence of false-positive mRDTs, defined as mRDT(+)/microscopy(−), using data from the 2018–2019 Uganda Malaria Indicator Survey (MIS). Children aged <5 years (under-5s) with paired mRDT and microscopy results were included. We estimated the prevalence of false-positive mRDTs among microscopy(−) children using survey weights. We fit bivariate generalized linear models to estimate the prevalence difference (PD) of false-positive mRDTs for pre-specified covariates. We constructed cross-validated weighted lasso regression models to determine which variables best predict false-positive mRDTs among children with recent fever.

The prevalence of false-positive mRDTs was 10.7% (849/6786) and was strongly correlated with region-level transmission intensity. Prevalence was higher among children with recent fever (PD: 17.2%; 95% CI: 13.7%, 20.6%), recent antimalarial use (14.7%; 7.1%, 22.3%), and comorbid anemia (8.1%; 5.9%, 10.3%). Prevalence was lower among those with recent antibiotic use (−17.6%; −22.5%, −12.7%). A model with clinical, environmental, and household variables better predicted false-positive mRDTs (weighted AUC = 0.79) than individual models.

False-positive mRDTs are prevalent among under-5s in the 2018–19 Uganda MIS and lead to overestimates of community-level malaria prevalence. These results suggest that false-positive mRDTs may also contribute to misdiagnosis and unnecessary antimalarial use in clinical settings.

In the 2018–2019 Uganda Malaria Indicator Survey, false-positive mRDTs were frequent among children under 5. Clinical factors can be used to predict false-positive results among children with recent fever. Antimalarial overprescription due to false-positive mRDTs may accelerate emerging drug resistance.