Objectives. We sought to identify people living with HIV/AIDS from Medicare
and Medicaid claims data to estimate Medicaid costs for treating HIV/AIDS in
California. We also examined how alternate methods of identifying the relevant
sample affect estimates of per capita costs.
Methods. We analyzed data on Californians enrolled in Medicaid with an HIV/
AIDS diagnosis reported in 2007 Medicare or Medicaid claims data. We
compared alternative selection criteria by examining use of antiretroviral drugs,
HIV-specific monitoring tests, and medical costs. We compared the final sample
and average costs with other estimates of the size of California’s HIV/AIDS
population covered by Medicaid in 2007 and their average treatment costs.
Results. Eighty-seven percent (18 290) of potentially identifiable HIV-positive
individuals satisfied at least 1 confirmation criterion. Nearly 80% of confirmed
observations had claims for HIV-specific tests, compared with only 3% of
excluded cases. Female Medicaid recipients were particularly likely to be
miscoded as having HIV. Medicaid treatment spending for Californians with
HIV averaged $33 720 in 2007.
Conclusions. The proposed algorithm displays good internal and external
validity. Accurately identifying HIV cases in claims data is important to avoid
drawing biased conclusions and is necessary in setting appropriate HIV
managed-care capitation rates. (Am J Public Health. 2015;105:567–574. doi:10.
2105/AJPH.2014.302263)