642 - Trends and cost burden of Legionella urine antigen test

Background: Legionella urine antigen (LUAg) testing is used to identify the pathogen Legionella pneumophila serotype 1 which accounts for 50 to 70% of Legionella pneumonia and has 80% sensitivity and 95% specificity. The 2019 ATS/IDSA CAP guidelines recommend against routinely testing urine for LUAg except when indicated by epidemiological factors or severe cases of CAP; however, the recommendation is based on a low quality of evidence. In 2014 & 2015 there were 32 and 39 cases, respectively in the state of Mississippi. The purpose of this study was to evaluate the trends of ordering LUAg, positive results and estimate the cost burden at the University of Mississippi Medical Center (UMMC).

Methods: We performed a retrospective study of all patients who received the LUAg test at UMMC from January 3, 2013 to December 31, 2019. Patient Cohort Explorer was used to obtain de-identified patient data from EPIC. We obtained the number of encounters and patients on whom the LUAg test was performed during their inpatient hospitalization. Coding and billing offices provided the cost per LUAg test.

Results: LUAg test was ordered 2,642 times on 2350 patients between 2013 and 2019. 22 LUAg test results were positive in 21 patients. 2,627 tests were done on patients admitted in the hospital. Of the 1,181 tests ordered in female patients, 11 were positive and of the 1461 tests done in male patients, 11 were positive. The minimum age for ordered test was under 1 year while the oldest patient is 89 years old with a median age of 57 years. The youngest patient to be positive is 21 and the oldest patient was 72 years. 1,471 tests were done in African American patients and 1084 tests in Caucasian patients. At the end of study period 1901 were alive and 741 deceased. The median length of stay for the patient receiving the test was 7 days with 1726 patients discharged within 10 days. 174, 255, 301, 433, 467, 395, 613 tests were ordered respectively from 2013 to 2019. At self pay cost of $132.82 in 2019 USD, the total cost of 2642 tests was $350,910.44. About $15,950.47 was spent for each positive LUAg test during the study period.

Conclusion: Incidence of pneumonia from Legionella in Mississippi is low. Based on our study, we recommend to follow the current ATS/IDSA guidelines and order the test in select patients as recommended, in efforts to reduce diagnostic costs.