CHICAGO – The rate of skin and soft tissue infections in Americans younger than 65 years old increased by approximately 11% between 2005 and 2008, a study has shown.
Using national projections of incidence and costs from a population of commercially insured individuals, the study indicated "that more than 11 million skin and soft tissue infections occur annually in Americans younger than 65 years old, with an annual associated medical cost of almost $24 billion," Dr. Loren G. Miller reported at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
Although incidence data from the early 2000s linked the emergence of community-associated methicillin-resistant Staphylococcus aureus with a dramatic increase in skin and soft tissue infections [SSTIs], "more recent data on the [SSTI] incidence rates and treatment costs are lacking," Dr. Miller said in a poster presentation.
To estimate updated SSTI incidence rates and the related health care utilization costs, he and his colleagues examined ambulatory and inpatient data from 2005 to 2008 for approximately 24 million Americans between 0 and 64 years using the HealthCore Integrated Research Database, a longitudinal health care claims database.
The investigators extracted data for SSTI diagnoses based on ICD-9 codes and estimated the annual SSTI incidence by diagnosis setting and age group. They also estimated complication rates by SSTI type, the direct medical costs associated with SSTI claims, and national projections of SSTI cases, explained Dr. Miller, director of the infection care program at Harbor-UCLA Medical Center in Torrance, Calif.
From the 2005 to 2008 data, "we identified more than 1.5 million [SSTIs], 95% of which were diagnosed in the ambulatory setting," he said. Of the 1,506,882 SSTIs identified, 60% were classified as abscesses or cellulitis.
During the 4-year period of investigation, the incidence of SSTIs increased from 41.0/1,000 person-years to 45.5/1,000, with the highest incidence of both ambulatory onset and inpatient onset observed in those aged 45-64 years. In this age group the incidence of SSTI was 42.26/1,000 person-years with ambulatory onset and 3.39 with inpatient onset.
A total of 1.2% of the ambulatory group and 24.1% of the inpatient group developed at least one SSTI complication, including myositis, osteomyelitis, gangrene, and sepsis. In addition, 1.48% of the ambulatory group and 9.8% of the inpatient group required subsequent hospitalization for SSTI-related complications.
"The complication rates depended on the type of infection and the setting of the initial diagnosis," he said. In both the ambulatory-onset and inpatient-onset groups, decubitus ulcers and nonhealing surgical wounds were associated with the highest complication rates.
Based on the acquired data, the 2010 projected annual cost associated with SSTIs in the United States in this population was approximately $24 billion, an amount comparable to the overall U.S. hospital costs associated with back pain, cardiac dysrhythmias, or acute cerebrovascular disease. The mean direct medical cost associated with an initial SSTI was $2,107, and the median cost was $249.
The generalizability of the findings is limited by the study design, specifically the lack of data for individuals older than 64 years and those without insurance, the absence of data on the microbiologic etiology of the SSTIs, and the fact that the accuracy of ICD-9 SSTI diagnoses are not well validated. Still, the estimated incidence of 4 SSTIs per 100 person-years in this population and the high associated health care costs suggest that targeted interventions to prevent SSTIs "could reduce morbidity and health care resource utilization substantially," Dr. Miller concluded.
Dr. Miller disclosed financial relationships with GlaxoSmithKline, Cubist, and Pfizer. GlaxoSmithKline provided funding for this study.