摘要：Objectives. We determined differences in Medicaid service use and health care costs in a rural Indian Health Service (IHS) user population of American Indians and Alaska Natives as compared with Whites. Methods. California Medicaid eligibility and claims files were linked to IHS user files to obtain a sample of Medicaid-eligible American Indian/Alaska Native users (n=7910). A random sample of Whites was matched for age, gender, aid category, length of eligibility, and county of residence (n=15075). We used generalized linear models to compare risk-adjusted use of resources—ambulatory visits, prescriptions, emergency room visits, hospitalizations, and costs—both adjusting and stratifying for dominant source of ambulatory visits. Results. American Indians/Alaska Natives had significantly lower use of Medicaid-paid ambulatory visits, prescriptions, emergency room visits, and hospitalizations and lower associated costs than Whites. Medicaid-paid total costs and use of services were lower for those who predominantly used Indian health program clinics, as well as for those who predominantly used other sources of ambulatory care. Conclusions. Barriers to receiving Medicaid services and payments exist for American Indians/Alaska Natives in the rural IHS-user population. If American Indians/Alaska Natives are to have Medicaid resources comparable to those of Whites, these barriers must be reduced. Disparities in Medicaid payments for American Indians/Alaska Natives compared with those for non-Indians raise issues of whether American Indians/Alaska Natives are receiving all Medicaid-funded services to which they are entitled and whether the services received are appropriately billed by providers and paid by Medicaid. In states with substantial populations of American Indians/Alaska Natives, Medicaid per capita costs of medical care services for American Indians/Alaska Natives are two thirds those of the services for the eligible population as a whole. 1 , 2 American Indians/Alaska Natives, however, generally have a lower health status than Whites and are expected to have a higher volume of service use and costs. 2 – 7 Medicaid is of growing importance to American Indians/Alaska Natives who are eligible for health care through the Indian Health Service (IHS). 8 , 9 American Indians/Alaska Natives in the IHS system currently receive only half the per capita health care funding needed, as determined by actuaries. 4 , 10 IHS services are available to members (or descendents of members) of federally recognized tribes who live on or near Indian lands where there are either IHS direct services or tribal providers of IHS-funded services. 7 , 11 Any American Indians/Alaska Natives who meet Medicaid financial eligibility requirements of the state in which they reside, however, are entitled to Medicaid coverage whether or not they are also eligible for IHS-funded services. For American Indians/Alaska Natives who use the IHS system, Medicaid is considered the primary payer, and IHS is considered the payer of last resort. Although there are financial incentives for providers to bill Medicaid for services that eligible American Indians/Alaska Natives receive, it is possible that the IHS may pay for some ambulatory visit or prescription drug services for American Indians/Alaska Natives eligible for Medicaid; this is considered an inefficient use of declining IHS funds. 2 Neither Medicaid nor IHS information alone can be used to compare American Indian/Alaska Native (AIAN) service use and costs with those of Whites. Race/ethnicity is not reliably indicated on Medicaid eligibility records, leaving little information on the eligibility or utilization of Medicaid services by American Indians/Alaska Natives. 12 Medicaid services used outside the IHS provider system are not included in IHS records. 9 Additionally, most of the 12 administrative IHS areas consist of parts or all of multiple states. Thus, Medicaid utilization and costs in most IHS areas are determined by multiple state Medicaid regulations. Linking Medicaid and IHS information for the AIAN user population in a single state that is also a single IHS administrative area makes it possible to investigate disparities in Medicaid utilization and costs. California is 1 of 2 IHS areas that consist of 1 state and is also 1 of 22 states in which per capita costs for Medicaid-eligible persons identified as AIAN in rural and urban eligibility files are less than two thirds (60%) those of Medicaid-eligible persons as a whole. 1 We present a study that linked Medicaid and IHS information to compare California Medicaid service use and costs in the IHS user population with those in the White population. Because all areas of the IHS system have commonalities and differences, no single area is necessarily representative. 13 We therefore briefly provide background on the California area IHS user population and its IHS-funded services compared with those of other areas of the IHS system.
