Sensitivity of ID NOW and RT-PCR for detection of SARS-CoV-2 in an ambulatory population

Abstract

Diagnosis of SARS-CoV-2 (COVID-19) requires confirmation by reverse transcription-polymerase chain reaction (RT-PCR). Abbott ID NOW provides fast results but has been criticized for low sensitivity. Here we determine the sensitivity of ID NOW in an ambulatory population presented for testing. The study enrolled 785 symptomatic patients, of whom 21 were positive by both ID NOW and RT-PCR, and 2 only by RT-PCR. All 189 asymptomatic patients tested negative. The positive percent agreement between the ID NOW assay and the RT-PCR assay was 91.3%, and negative percent agreement was 100%. The results from the current study were included into a larger systematic review of literature where at least 20 subjects were simultaneously tested using ID NOW and RT-PCR. The overall sensitivity for ID NOW assay was calculated at 84% (95% confidence interval 55-96%) and had the highest correlation to RT-PCR at viral loads most likely to be associated with transmissible infections.

Keywords: COVID-19; ID NOW; RT-PCR; SARS-CoV-2; ambulatory; human; medicine; sensitivity.

Figure 1.. PRISMA 2009 flow diagram detailing the studies that were identified, screened, deemed eligible, and finally included in the analysis.

Note that the data from the current clinical evaluation has been included in the analysis.

Figure 2.. Forest plots demonstrating the three studies with low risk of patient selection bias utilized in the meta-analysis.

(A) The sensitivity of ID NOW as compared with the reference standard, and the overall sensitivity was estimated to be 82% with a lower 95% confidence bound at 67% and an upper bound of 91%. (B) The sensitivity of RT–PCR and is estimated to be 98% with a 95% CI of 96–99%.

Figure 3.. Cycle number distributions for 1182 symptomatic (A) and 164 asymptomatic (B) patients who tested positive for SARS-CoV-2 between July 14 and November 16, 2020, using the Abbott m2000 assay at The Everett Clinic.

For patients with multiple tests, only the first positive test is included. In (C), data for each group of patients has been normalized so that the sum of all bins is 100, allowing better comparison of the distributions. The Abbott m2000 cycle number is generally about 10 cycles less than the Ct reported for PCR assays on other devices.

Figure 4.. The collection methodology to ensure proper randomized sampling of nares for simultaneous analysis for SARS-CoV-2 by the ID NOW isothermal amplification and Hologic Panther RT–PCR assays.

A total of two swabs was collected on each patient, with patients having an even birth year number the right nares were collected first followed by a second swipe in the left nares and then for ID NOW point-of-care (POC) testing (depicted as red swab). For those patients, the other swab (blue swab) was sent for SARS-CoV-2 RT–PCR analysis by the Hologic Panther assay. For patients having an even birth year, the swabs sent for testing was reversed with the blue swab sent for ID NOW testing and the red swab sent for RT–PCR analysis.