Testing Frequency Matters | An Evaluation of the Diagnostic Performance of a SARS-CoV-2 Rapid Antigen Test in United States Correctional Facilities

Abstract

Background

The CDC recommends serial rapid antigen assay collection within congregate facilities. Though modeling and observational studies from communities and long-term care facilities have shown serial collection provides adequate sensitivity and specificity, the accuracy within correctional facilities remains unknown.

Methods

Using Connecticut Department of Corrections (DOC) data from November 21^st 2020 to June 15^th 2021, we estimated the accuracy of a rapid assay, BinaxNOW, under three collection strategies, single test collection and serial collection of two and three tests separated by 1-4 days. The sensitivity and specificity of the first (including single), second, and third serially collected BinaxNOW tests were estimated relative to RT-PCRs collected within one day of the BinaxNOW test. The accuracy metrics of the testing strategies were then estimated as the sum (sensitivity) and product (specificity) of tests in each strategy.

Results

Of the 13,112 residents who contributed ≥1 BinaxNOW test during the study period, 3,825 contributed ≥1 RT-PCR paired BinaxNOW test. In relation to RT-PCR, the three-rapid antigen test strategy had a sensitivity of 95.9% (95% confidence intervals (CI): 93.6-97.5%) and specificity of 98.3% (CI: 96.7-99.1%). The sensitivity of the two- and one-rapid antigen test strategies were 88.8% and 66.8%, respectively, and the specificities were 98.5% and 99.4%, respectively. The sensitivity was higher among symptomatic residents and when RT-PCRs were collected before BinaxNOW tests.

Conclusions

We found serial antigen test collection resulted in high diagnostic accuracy. These findings support serial collection for outbreak investigation, screening, and when rapid detection is required (such as intakes or transfers).