Performance of Abbott ID‐Now rapid nucleic amplification test for laboratory identification of COVID‐19 in asymptomatic emergency department patients

Abstract

Abstract Objective We sought to evaluate the test characteristics of Abbott ID‐Now as a screening tool compared to polymerase chain reaction (PCR) testing for identification of COVID in an asymptomatic emergency department population. Methods We performed a prospective study enrolling a convenience sample of asymptomatic patients presenting to a single academic emergency department (ED) who received simultaneous testing with ID‐Now and PCR per standardized ED protocols. Sensitivity, specificity, and positive and negative predictive value (PPV, NPV) of ID‐Now were calculated compared to PCR. Stratified analysis by cycle threshold (Ct) values was also performed, defined as high viral load (Ct < 33) and low viral load (Ct ≥ 33). Results A total of 3121 patients were enrolled, of whom 2895 had valid results for ID‐Now and PCR. COVID prevalence was 2.6%. ID‐Now had a sensitivity of 85.1% (95% CI 75.9% to 92.7%) and a specificity of 99.7% (99.5% to 99.9%). PPV and NPV were high at 87.5% (83.1% to 96.1%) and 99.6% (99.3% to 99.8%). Stratified analysis by low and high Ct values demonstrated reduction in sensitivity in patients with low viral loads: 91.7% (81.6% to 97.2%) in low Ct value patients versus 58.3% (27.7% to 84.8%) in high Ct value patients. Conclusions ID‐Now had excellent performance in asymptomatic ED patients with a low rate of false positives. Cycle threshold analysis suggests a relationship between viral load and ID‐Now sensitivity. Given its speed and performance in this population, ID‐Now should be considered an excellent tool to support clinical decision‐making in ED populations.

Keywords

• COVID‐19
• diagnostic testing
• point‐of‐care testing
• triage
• validation