An optimized stepwise algorithm combining rapid antigen and RT-qPCR for screening of COVID-19 patients

Area of Science:

• Medical diagnostics
• Infectious disease research
• Public health

Background:

• The COVID-19 pandemic necessitated rapid and accurate diagnostic methods.
• Optimizing detection strategies is crucial for controlling viral outbreaks.
• Evaluating the performance of rapid antigen detection (RAD) alongside RT-qPCR is essential.

Purpose of the Study:

• To investigate the efficacy of a stepwise combination of RAD and RT-qPCR for COVID-19 detection.
• To compare the diagnostic accuracy of RAD versus RT-qPCR.
• To assess the impact of cycle threshold (Ct) and time from symptom onset (TSO) on diagnostic performance.

Main Methods:

• A total of 43,399 patients were screened for COVID-19 using RT-qPCR.
• Nasopharyngeal swabs were collected for testing.
• A subset of 200 positive cases underwent RAD testing for comparative analysis, with Ct and TSO as covariates.

Main Results:

• RAD demonstrated an overall sensitivity of 72% and specificity of 99% compared to RT-qPCR.
• Sensitivity of RAD was significantly higher in patients with Ct ≤ 25, particularly within 4 days of symptom onset or in asymptomatic individuals.
• Combining RAD and RT-qPCR could reduce the number of RT-qPCR tests required by up to 4%.

Conclusions:

• Using RAD alone carries a risk of misdiagnosing 28% of COVID-19 cases.
• A stepwise approach combining RAD and RT-qPCR presents an efficient screening procedure for COVID-19.
• This optimized strategy can aid in facilitating the control of COVID-19 outbreaks.