Cost associated with the treatment of influenza in a managed care setting

The purpose of this study was to assess the costs and treatments associated with influenza patients with and without secondary viral or bacterial infections in a managed care setting.

Patients with influenza diagnoses (ICD-9 = 487) were identified in the PharMetrics database between January 1, 1997 and June 30, 1998. Patients were placed into 3 cohorts: influenza only (INF), influenza plus a secondary bacterial respiratory infection (BRI), and influenza plus a secondary viral respiratory infection (VRI). The index date was defined as the date of the first occurrence of an influenza diagnosis during the study period. Medical claims were assessed from the index date to the end of the influenza episode, which was defined as the date of the last claim for influenza followed by a 90-day "clean period" during which no influenza-related charges occurred.

A total of 18,000 patients met the inclusion criteria. The mean age was 29 years, and 54% were female. Approximately 93% of patients were placed in the INF cohort, and 3% each in the BRI and VRI groups. The BRI cohort had the highest mean total cost ($5593* SD = 10,939), compared with the VRI cohort ($847 SD = 1782) and INF cohort ($602 SD = 2813) (P less than.0001 vs INF; P less than.0001 vs VRI). This total cost disparity was primarily driven by differences in inpatient costs: BRI ($3509, SD = 9474); VRI ($208, SD = 1327); INF ($138, SD = 2145). Patients in the BRI cohort averaged 0.5 hospitalizations per patient vs 0.06 in the VRI cohort and 0.03 in the INF cohort.

Subjects in the BRI cohort were significantly more costly and had an increased risk of hospitalization as compared with subjects in the VRI or INF cohorts. Early intervention with antiviral agents and/or antibiotics, where appropriate, could result in significant cost savings for managed care organizations.