1885. Experience using combined antigen and RT-PCR tests for COVID-19 diagnosis at a Veterans Affairs (VA) Health Care System during the Omicron surge


 
 
 Combining rapid antigen and RT-PCR tests optimizes detection of COVID-19 compared with either test alone. Therefore, coincident with the Omicron surge, in November 2021, the Atlanta VA Health Care System (AVAHCS) initiated combination testing for all patients admitted from the emergency department (ED) to the inpatient wards. We retrospectively compared test performance for all patients with combination testing performed at AVAHCS, assessed impact of combination testing on ED disposition, and reviewed clinical characteristics of those admitted from the ED with discordant results.
 
 
 
 We assessed concordance of antigen (Abbott BinaxNOW®) and RT-PCR (either Cepheid GeneXpert® or Roche cobas® 6800) tests performed within 24 hours of each other (i.e., combination test-pairs) for any patient during November 25, 2021–January 27, 2022, and calculated test characteristics of the antigen test using RT-PCR as the gold standard. For those patients evaluated in the ED who had discordant results, we determined ED disposition then performed standardized medical record reviews for those admitted to ascertain clinical history and hospital course and disposition.
 Combination Antigen and RT-PCR Testing Algorithm for Patients in the Emergency Department, Atlanta VA Healthcare System
 
 
 
 Of 836 combination test-pairs, 112 (13%) were discordant, of which 111 were antigen-negative/RT-PCR positive. Sensitivity of the antigen test was 50%, specificity was 100%, positive predictive value 99%, and negative predictive value was 85%. Of 68 patients evaluated in the ED who had antigen-negative/RT-PCR positive results, 21 (31%) were admitted, of whom 17 (81%) had COVID-19-related symptoms at time of ED evaluation. Of the 21 admitted patients, all were admitted to a COVID isolation unit, 20 (95%) had ≥1 chronic comorbidity, 12 (57%) had not completed vaccination, 14 (67%) received COVID-19-specific treatment while inpatient, 6 (29%) received care in an intensive care unit, 17 (81%) discharged home, and 1 (5%) died during hospitalization.
 Flow Diagram of Initial Analysis
 Flow Diagram of ED Discordant Results
 Characteristics of Discordant Hospitalized Patients
 
 
 
 The sensitivity of antigen testing was 50% compared to RT-PCR among patients tested across AVAHCS, consistent with published literature. Combination testing facilitated earlier diagnosis, isolation, and treatment of some patients hospitalized from the ED, likely preventing nosocomial transmission.
 
 
 
 All Authors: No reported disclosures.
