Multisite Clinical Validation of Isothermal Amplification-Based SARS-CoV-2 Detection Assays Using Different Sampling Strategies.

Isothermal amplification-based tests have been introduced as rapid, low-cost, and simple alternatives to real-time reverse transcriptase PCR (RT-PCR) tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection. The clinical performance of two isothermal amplification-based tests (Atila Biosystems iAMP coronavirus disease of 2019 [COVID-19] detection test and OptiGene COVID-19 direct plus RT-loop-mediated isothermal amplification [LAMP] test) was compared with that of clinical RT-PCR assays using different sampling strategies. A total of 1,378 participants were tested across 4 study sites. Compared with standard of care RT-PCR testing, the overall sensitivity and specificity of the Atila iAMP test for detection of SARS-CoV-2 were 76.2% and 94.9%, respectively, and increased to 88.8% and 89.5%, respectively, after exclusion of an outlier study site. Sensitivity varied based on the anatomic site from which the sample was collected. Sensitivity for nasopharyngeal sampling was 65.4% (range across study sites, 52.8% to 79.8%), for midturbinate was 88.2%, for saliva was 55.1% (range across study sites, 42.9% to 77.8%), and for anterior nares was 66.7% (range across study sites, 63.6% to 76.5%). The specificity for these anatomic collection sites ranged from 96.7% to 100%. Sensitivity improved in symptomatic patients (overall, 82.7%) and those with a higher viral load (overall, 92.4% for cycle threshold [