Health care utilization by adolescents on medicaid: implications for delivering vaccines.

OBJECTIVE: To examine the degree to which current health care utilization patterns of Medicaid-enrolled adolescents living in Michigan would allow opportunities for adolescent immunizations to be provided.
METHODS: Outpatient claims data from 2001-2005 were analyzed for 11- to 18-year-old Medicaid-enrolled adolescents living in Michigan. Visits were classified as either health-maintenance examinations (HMEs) or problem focused by using diagnostic and procedural codes. Data were divided into 4 overlapping 2-year time periods, and the age-specific proportion of adolescents who attended these 2 visit types was calculated for each. chi(2) tests were used to evaluate associations of visit patterns with gender.
RESULTS: Of the 718847 adolescents included in the study, <50% had >or=1 HME visit within any 2-year time period, and substantially fewer (<15%) had annual HMEs. In contrast, at least 75% of the adolescents had >or=1 problem-focused visit in any given 2-year period, and approximately half had participated in at least 2 problem-focused visits. Problem-focused, but not HME, visit utilization was significantly associated with gender, with girls increasing, but boys decreasing, visit utilization as they aged.
CONCLUSIONS: Similar to privately insured adolescents, most Medicaid-enrolled adolescents do not have annual preventive-care visits, which calls into question the feasibility of providing immunizations primarily at annual HMEs. Participation in problem-focused encounters was generally high in our study. However, even problem-focused visit utilization was low among older adolescent boys. This suggests that in addition to strengthening immunization within the medical home, alternative venues for reaching certain subpopulations of adolescents should also be developed.