The Performance of Antigen-detecting Rapid Diagnostic Test Among COVID-۱۹ Outbreaks in North-Eastern Peninsular Malaysia

Background and aims: Accurate and timely diagnosis is crucial for coronavirus disease ۲۰۱۹ (COVID-۱۹) outbreaks. Antigen-detecting rapid diagnostic tests (Ag-RDTs) are easily accessible and affordable, producing rapid results. They are an alternative to the limited gold-standard real-time reverse-transcription polymerase chain reaction (rRT-PCR) tests. This study assessed the performance of Ag-RDTs for COVID-۱۹ outbreaks in institutional settings with high disease prevalence in Kelantan State, Malaysia. Methods: This study analyzed a total of ۳۰۳ individuals from five institutional outbreaks with paired nasopharyngeal specimens tested for COVID-۱۹ by Ag-RDTs and rRT-PCR. The diagnostic performance of Ag-RDTs was evaluated through rRT-PCR as the gold standard based on cycle threshold (Ct) value, disease prevalence, and manufacturers. Results: There was a moderate agreement between Ag-RDTs and RT-PCR (κ = ۰.۶۰۳; ۹۵% CI: ۰.۵۲۰- ۰.۶۸۶; P < ۰.۰۰۱). The overall specificity was ۹۷.۹% (۹۵% CI: ۹۴.۱%-۹۹.۶%), sensitivity was ۶۳.۳% (۹۵% CI: ۵۵.۳%-۷۰.۸%), accuracy Ag-RDTs was ۸۱.۲% (۹۵% CI: ۷۶.۴%-۸۵.۵%), while positive and negative predictive value was ۹۶.۶% (۹۵% CI: ۹۰.۲%-۹۸.۹%) and ۷۴.۱% (۹۵% CI: ۷۰.۰%-۷۷.۹%), respectively. Further, lower median Ct was reported in ۱۰۰ (۳۳.۰%) true-positive cases compared to ۵۸ (۱۹.۱%) false-negative cases (۲۰.۳ vs ۳۱.۴, P < ۰.۰۰۱). The sensitivity was higher (P < ۰.۰۰۱) in those with high viral load (Ct value ≤ ۲۵.۰) with better performance and a prevalence > ۱۰%. In addition, no significant difference was observed between the studied manufacturers. Conclusion: The Ag-RDTs performed well in diagnosing COVID-۱۹ among outbreaks with higher viral load and disease prevalence. High-risk cases tested negative by Ag-RDTs may have low viral load and require confirmation by rRT-PCR.

Keywords:

accuracy , COVID-۱۹ , Diagnostic performance , Rapid antigen test