424 - Sensitivity Results for the Abbott m2000 PCR Assay of SARS-CoV-2 at a Denver, Colorado Medical Center

Background: The Abbott RealTime SARS-CoV-2 assay (Abbott Laboratories, Chicago, Illinois) is an RT-PCR test for qualitative detection of SARS-CoV-2 nucleic acid in NP and OP specimens performed on the Abbott m2000 System. Currently, no published data exists on the performance characteristics of the assay.

Methods: Denver Health Medical Center (DHMC) is a 550-bed hospital that is Denver County’s safety net institution. The Department of Pathology and Laboratory Services at DHMC provides testing for both inpatient and outpatient populations. In March 2020, we validated the Abbott RealTime SARS-CoV-2 assay. Beginning March 19, inpatients and outpatients with SARS-CoV-2 symptoms were tested. On April 22, universal testing began on admitted patients, regardless of symptoms, and on May 2, testing began on asymptomatic outpatients prior to time-sensitive procedures. We evaluated the sensitivity and negative predictive value (NPV) for tests done March 19 through June 16 using a surrogate method. False negative (FN) results: patients with an initial negative test then a positive test within 7 or 14 days. True negative (TN) results: patients with two initial consecutive negative tests within 7 or 14 days. True positive (TP) results: patients with an initial positive test.

Results: There were 16,152 tests done for 13,673 patients. Test results are shown in Table 1. Sensitivity for 7 and 14 days was 99.1% and 97.6%, respectively. The NPV for 7 and 14 days was 94.7% and 91.4%, respectively.Table 1


Conclusion: There are limitations to our analysis. First, our assumption of no false positives may be incorrect. Although PCR assays are known to have a low false positive rate, the rate likely is not zero, but in the absence of a true gold standard comparator, we could not calculate test specificity. Second, testing asymptomatic patients may artificially inflate the TN results and the NPV. Third, results depend on the quality of specimen collection, preservation, transport, and handling. We believe accounting for repeat testing in a short timeframe lends credibility to the sensitivity and NPV results. Without published gold standard data on SARS-CoV-2 testing, infection can be reliably ruled both in and out using this assay. Providers can confidently use the results to make clinical and infection prevention management decisions.