Improving estimates of prevalence of current asthma among Medicaid enrollees by analyzing reported ICD-9 codes on service claims and asthma-related prescription fills in CY 2001: Analyses of asthma acute or ambulatory care, or non-asthma care with a reported secondary diagnosis of asthma

Childhood asthma prevalence is estimated by the NHIS survey and adult asthma by the BRFSS. Medicaid accounts for a large proportion of the asthma burden on health services and expenditures for this condition, however Medicaid prevalence is not known. The purpose of the presentation is to discuss an approach to improve estimates of prevalence among Medicaid enrollees. We used the 2001 CMS Medicaid eXtract (MAX) research files for each state and the District of Columbia (all fee-for-service and primary case management claims; plus encounter claims submitted by the states – albeit largely underreported. Overall, 4.6% (2,292,406) of the 50,078,316 Medicaid population had a primary or a secondary diagnosis of asthma (1,597,585 = primary; 694,821 = secondary) = current asthma. Asthma burden analyses considered only the Medicaid claims with an ICD-9 diagnosis of 493= asthma except the approach for asthma-related prescription fills differed because there is no diagnosis on those claims. 97,496 individuals (4.3%) were hospitalized for asthma; 1,570,972 individuals (69 %) had ambulatory care.

For prescription fills, the computation of burden included any asthma-related fills for individuals with a primary or secondary diagnosis of asthma. Many received prescription fills who did not have an asthma service. Findings showed that 82% (1,878,550) of individuals with current asthma had one or more asthma-related prescription fills. Additional analyses controlled for type of payment claim (paid by service or capitated encounter) fee-for-service, gender, race/ethnicity and age groups (children, working-aged adults, and the elderly). Challenges remain for more complete reporting of asthma encounter claims.