Evaluation of Flu A/B, SARS-CoV-2, and RSV Antigen Combo Rapid Test in Hospitalized Children Under Two Years of Age

<b>Background/Objectives</b>: Next to malaria, respiratory viruses, particularly respiratory syncytial virus (RSV), are responsible for the hospitalization and death of thousands of young children each year in sub-Saharan Africa. During peak seasons, conducting separate tests is time-consuming and distressing. This underscores the need for efficient, rapid multiplexed diagnostic tools. This study aimed to evaluate the clinical performance of a lateral flow assay (LFA) based antigen combo rapid diagnostic test (ML Ag Combo RDT, manufactured by MobiLab) that detects RSV, influenza viruses A and B (Flu A/B), and SARS-CoV-2. <b>Methods</b>: The Allplex panel 1 rRT-qPCR assay was used as a reference assay to evaluate the clinical performance of the LFA Ag Combo RDT in pediatric hospital settings. It was performed using 470 nasopharyngeal swab (NPS) specimens from hospitalized children under two years of age with respiratory symptoms. <b>Results</b>: Based on the comparative analysis of the testing results for 470 NPS, the ML Ag Combo RDT demonstrated high sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 90.06%, 98.38%, 93.67, and 97.39% for RSV, and 30%, 100%, 100%, and 95.43 for Flu A/B, respectively. Agreement with the Allplex panle1 1 rRT-qPCR was strong (κ = 0.90 for RSV) and moderate (κ = 0.45 for Flu A/B), with overall accuracies of 96.63% for RSV and 95.5 for Flu A/B. This was further supported by ROC analysis for aggregated data (RSV and, Flu A/B) with an AUC value of 0.925. As expected, in samples with high viral loads (Ct < 20), the Ag Combo RDT achieved 100% sensitivity for RSV and Flu A/B. Sensitivity declined slightly at lower viral loads (Ct > 35). <b>Conclusions</b>: The ML Ag Combo RDT demonstrates high specificity and diagnostic accuracy for the detection of RSV and Flu A/B in pediatric hospital settings where timely diagnosis is critical.