OBJECTIVES: The aims of this research were to (1) compare onychomycosis infection rates in patients with and without diabetes, and (2) determine the impact of onychomycosis on the development of secondary infections in the diabetic population. METHODS: Patients with onychomycosis or diabetes were identified from the Clinical Care in America (CCIA) Managed Care database. Those continually enrolled in a one-year period between 1995-1996 were classified as having onychomycosis with or without diabetes and rates of secondary infection within the following 12 months were analyzed adjusting for age and gender. Using the 1995 MEDSTAT database of diabetic claims, patients with a claim for onychomycosis along with a random sample of those without onychomycosis were identified in addition to frequency of secondary infection. Logistic regression was used to estimate the relative risk of developing gangrene or foot ulcer adjusting for age and uncomplicated diabetic payments. RESULTS: In CCIA, onychomycosis was more prevalent in diabetic patients (5.9%) relative to patients without diabetes (0.8%). Likewise, the secondary infection rate among diabetics with onychomycosis was higher relative to diabetics without onychomycosis (15% and 6%, respectively). Diabetic patients with onychomycosis in MEDSTAT had a higher percent of gangrene and foot ulcer (12.2%) relative to those without onychomycosis (3.8%) and had an approximate three-fold higher risk of developing gangrene or foot ulcer. CONCLUSION: Results suggest that patients with diabetes may have higher rates of onychomycosis, which negatively impact the development of secondary infections (gangrene and foot ulcer), relative to patients without diabetes. The impact of onychomycosis on humanistic and economic outcomes in the diabetic population is the subject of current research, and should lend further evidence to support appropriate therapy. “ECONOMIC & OUTCOMES ISSUES OF GASTROINTESTINAL DISORDERS”