Health care resource utilization and costs for influenza-like illness among midwestern health plan members

BACKGROUND: Each year, 6%-20% of U.S. residents are infected by influenza, and more than 200,000 people are hospitalized due to complications related to influenza. In 2003, it was estimated that the direct medical costs for the treatment of influenza were $10.4 billion in the United States. OBJECTIVES: To (a) assess the current practice associated with the diagnosis and treatment of influenza-like illnesses (ILIs) in inpatient, ambulatory/ outpatient, and emergency room settings and (b) evaluate how the use of rapid influenza diagnostic tests (RIDTs) impacts patient health care utilization and cost in these clinical settings. METHODS: For this retrospective cohort study, patients with an influenzarelated health care encounter were identified using claims data from a midwestern commercial health insurance plan. In order to select the claims relevant to this study, the corresponding influenza ICD-9-CM codes, GPI codes, and CPT codes for the diagnosis, prescriptions, and procedures were identified and used to detect ILI claims. For the cost analysis of these data, the allowed amount in the billing claims was utilized. Using these data, the median cost, mean cost, minimum cost, and maximum cost were determined for each episode of care. The median costs were compared, and Wilcoxon two-sample tests and Kruskal-Wallis tests with a P value of 0.05 were used as the level of significance. RESULTS: Over 32% of the influenza-like illness episodes identified in this study involved empiric antiviral therapy as either treatment (15%) or prophylaxis (17.1%) without an accompanying medical visit. Of patient episodes with a medical visit, patients with an RIDT for influenza received antiviral treatment in 27.5% of the episodes compared with 55% of the episodes for patients with no RIDT. Episodes with a medical visit and an RIDT had statistically significant (P < 0.001) lower median 30-day influenzarelated health care costs ($62.46) than episodes with a medical visit but no RIDT ($192.83), as well as with empiric therapy but no accompanying medical visit ($105.64). CONCLUSIONS: The results of this analysis for ILI claims over a 2-year period suggest that utilization of RIDTs for influenza may reduce overall influenza-related health care costs and improve proper utilization of antiinfluenza medications.