152 Point-of-Care Influenza Testing Does Not Significantly Shorten Time to Disposition Among Emergency Department Patients With an Influenza-Like Illness

Abstract

Symptoms attributable to influenza-like illness are common presenting complaints to the emergency department (ED) during the winter months. The availability of anti-viral agents and the need to cohort patients with infectious diseases has increased the need to confirm the diagnosis of influenza (flu) prior to determining a disposition for patients. The objectives were to determine if time-to-disposition (TTD) was shorter among patients who were tested for influenza using a point-of-care (POC) test in a hospital ED compared to those who were tested in the hospital core laboratory (lab) and to determine if there was a difference in antibiotic use between groups. This study was conducted at an urban, safety net, academic level 1 trauma center. We conducted a prospective study that enrolled a convenience sample of ED patients for whom influenza testing was physician-ordered per usual ED clinical protocols during peak influenza season 2017. After consenting, subjects were randomized to either core lab testing (Xpert Flu, Cepheid) or POC testing (cobas Liat Influenza A/B, Roche Diagnostics) performed in the ED. Run times for the core lab assays and POC were 55-75 minutes and 20 minutes respectively. Data collected included demographics, chief complaint, results of influenza test, time to test results (TTTR, defined as time from when order was entered until results were available in the Electronic Medical Record), whether antibiotics were given, and TTD (defined as the time from when a patient was placed in the ED treatment room until the disposition (either admit, observe, or discharge) was ordered in the medical record. Descriptive statistics were calculated and group comparisons were made using a two sample t-test. Two hundred fifty-seven patients were approached of which 6 refused, and 51 were excluded (21 had comprehensive respiratory panels performed rather than exclusive influenza tests, 21 non-English speaking, 9 for other reasons). Two hundred subjects were enrolled, and 3 were dropped from the core laboratory arm due to incorrect test orders. Final study population included 97 in the core lab group and 100 in POC group. Demographic characteristics between core lab subjects and POC subjects were the same with respect to mean age, sex, and race. There were fewer flu positive results in the core lab group compared to the POC group (33.0% vs. 51.0%, p=.01) but a similar percentage of influenza type A (84.4% vs. 86.3%), and discharged patients (83.5% vs. 78.0%). The mean TTTR was 140.0min (SD 318.1min) for the core lab and 35.2min (SD 19.9min) for POC (p=.001). The mean TTD was 185.9min (SD 110.0) for the core lab group and 168.9min (SD 91.7) for POC (p=0.26). Antibiotics were given to 14.4% of core lab subjects, and 14.0% of POC subjects (p=0.93). Although use of a POC influenza test provided a more rapid time to test result than use of a core lab test, there was no statistically significant difference in time to disposition or antibiotic use between the groups. This is in contrast to other studies on POC testing in the ED setting. In this small study this finding may be due to the influence of other factors on disposition decisions in addition to diagnosis of influenza. Test implementation strategies for POC testing benefit from site-specific outcome studies in addition to reliance on published data from other institutions.