Impact of a Medicaid primary care provider and preventive care on pediatric hospitalization.

OBJECTIVE This study evaluates the impact that a Medicaid managed care program had on avoidable hospitalization, a form of health care misuse that we hypothesize can be reduced by improved access to and quality of primary care in the context of a managed care program. Ambulatory care sensitive (ACS) hospitalizations, a previously defined categorization of hospitalization, as well as all pediatric hospitalizations were also studied. INTERVENTION The Maryland Access to Care (MAC) was a fee-for-service, gatekeeper, Medicaid managed care program with assigned primary medical providers and required Early Periodic Screening, Diagnosis, and Treatment (EPSDT) examinations. Medicaid managed care elements include: 1) assignment to primary medical provider (PMP) either by voluntary choice or mandatory enrollment of eligible Aid to Families With Dependent Children (AFDC), Medical Assistance (medical needy), and Supplemental Security Income; 2) a medical home accessible 24 hours a day, 7 days a week; 2) PMP must authorize emergency department (ED), inpatient, and specialty care but there were no disincentives to PMP for referral; 3) fee-for-services reimbursement (with a physician rate increase) for primary care, authorized specialist care, and hospitalization; and 4) an on-line eligibility verification system was available to all medical providers. Pre-enrollment as well as publicity allowed MAC to be phased in rapidly, resulting in 70% to 80% enrollment by the end of the first program year. DESIGN The design of this study is that of a pre- and postevaluation of the MAC program using Medicaid claims analysis of data 3 years pre-MAC and 2 years post-MAC. In multivariate analyses, this study also compares MAC-enrolled children to non-MAC-enrolled children (before and after MAC began) to estimate the impact of MAC enrollment while controlling for potential confounders. SETTING State of Maryland from 1989 to 1993. PATIENTS MAC-eligible children 18 years of age. OUTCOME MEASURES Claims data were used to define avoidable hospitalization (based on ambulatory care received before hospitalization), to define ACS hospitalizations (based on the International Classification of Diseases-Clinical Modification, Ninth Revision [ICD-9-CM] codes), and to summarize use of ambulatory and inpatient care. ACS hospitalizations have been defined as those conditions for which timely and effective primary care can help to reduce the risk of hospitalizations. These are based solely on ICD-9-CM discharge codes that were studied by Billings and Teicholz in 1990 and used by an Institute of Medicine report in 1993. Examples include hospital discharge diagnoses of asthma (ICD-9-CM = 493), gastroenteritis (ICD-9-CM = 558.9), and dehydration (ICD-9-CM = 276.5). Usage measures, such as preventive care visits or ED visits, were created using Maryland Medicaid codes, Current Procedural Terminology codes, and ICD-9-CM codes. Linear regression was used to model trend. Logistic regression was used to model the probability of ambulatory and inpatient care given MAC enrollment and other covariates. First, logistic regression was used to predict the probability of any ambulatory care use among all MAC-eligible children during a quarter to model changes in access that may have occurred during MAC. Then, among users of ambulatory care or inpatient care, logistic regression was used to predict the probability of hospitalization. RESULTS Most of the children studied were in the AFDC program, about half were African-American, one third resided in Baltimore City, and 9% of children had ICD-9-CMs reflecting chronic disease. The mean percentage of time children were MAC-eligible per quarter was 91%. Only 5% of children were continuously enrolled for all 20 quarters included in this study. Per-capita ambulatory care visits, especially per-capita preventive care visits, increased significantly during the study period (b = 0.003) whereas per-capita ED visits did not change. The mean n