Cost and Utilization Comparisons Among Propensity Score-Matched Insulin Lispro and Regular Insulin Users

OBJECTIVES: To compare cost and utilization among users of insulin lispro and regular (human) insulin. METHODS: This was a retrospective analysis using administrative claims data for continuously enrolled subjects using insulin lispro or regular insulin between January 1, 1998, and December 21, 1999. Subjects were matched 1 to 1 on the propensity to receive lispro versus regular insulin using a score estimated from baseline characteristics such as age, gender, comorbidities, and oral hypoglycemic use. Once matched, 12 months of follow-up pharmacy and medical cost and utilization data (e.g. prescriptions, office visits, hospitalizations) from July 1,1997, through December 31, 2000, were analyzed using univariate statistics. RESULTS: Of 11,443 subjects, 3,341 (29.2%) had received a prescription for insulin lispro, while 8,102 (70.8%) had received a prescription for regular insulin. At baseline, lispro subjects tended to be younger, more often had type 1 diabetes and a history of insulin use, had fewer comorbidities, visited endocrinologists more often than family practice physicians, and had lower total costs. After matching on propensity score to within 0.01, 1,832 subject pairs were retained. On average, lispro subjects had significantly more office visits (P=0.0022) and pharmacy prescriptions (P=0.0165) but fewer inpatient hospital visits (P=0.0028)compared to regular insulin subjects. Cost results were similar, with insulin lispro subjects having significantly higher average office visit costs (P=0.0237) and pharmacy costs (P less than 0.0001) but lower inpatient hospital costs (P=0.0227). Total costs were not significantly different between treatment groups (P=0.5266). CONCLUSIONS: Total direct health care costs were not different between insulin lispro and regular insulin users. An association was observed between higher direct drug product cost and more intensive ambulatory care for insulin lispro users and lower inpatient hospital cost in the short-term.