Study population and setting
Validation was conducted using serial dilutions of two known SARS-CoV-2 positive samples and previously confirmed and consecutive positive patients to assess testing sensitivity after collecting samples in viral transport medium, and using 101 paired nasopharyngeal (NP) samples in viral transport media (VTM) (for the Cepheid-Xpert-Xpress SARS-CoV-2) and dry swabs of nares and NP samples (Abbot ID NOW) obtained from patients in the ED with a doctor ordered COVID-19 test at New York University Langone Tisch Hospital . Samples were analyzed 1-2 hours after collection.
Summary of Main Findings
Using serial dilutions of samples stored in viral transport medium demonstrated a high positive test agreement on a sample with a high viral load but low positive agreement on a sample with a lower viral load – reflective of the viral loads seen in many positive cases at this medical center. Sensitivity of Abbott ID NOW COVID-19 for dry swabs of nares and NP was 51.6% and 66.7% of swabs with viral transport media, compared to Xpert Xpress platform.
Strengths of this paper include comparison of platforms using both dry and VTM swabs as well as nares and NP samples. Each patient had multiple samples collected and validation was determined using various dilutions of samples.
The Abbot ID NOW is intended to be a POC test and was not utilized in that manner although the researchers did follow the manufacturer’s recommendations for testing 1-2 hours after collection. The study was conducted using a small convenience sample of patients all seeking care at one hospital ED over the course of 3 days. The validation was conducted against a single platform (Xpert Xpress) therefore discrepancies between the two tests could not be resolved. All patients (except one) had reported to the ED with symptoms of COVID-19, therefore test performance on asymptomatic individuals is unknown
Although Abbott ID NOW COVID-19 provides results in a shorter amount of time (5-13 min) compared to other platforms, it is not as sensitive as Xpert Xpress and additional validation is required to better understand the sensitivity of this test.
This review was posted on: 4 July 2020