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 theInternational Classification of Diseases–Clinical Modification, Ninth Revision [ICD-9-CM] codes), and to summarize use of ambulatory and inpatient care.

Avoidable hospitalizations include those conditions for which evidence exists that specific ambulatory care modalities reduce hospitalization rates. These hospitalizations were defined by combining the first ICD-9-CM on an inpatient claim with ambulatory and/or pharmacy claims for services before that hospitalization. The criterion of preceding ambulatory care was applied by linking dates of admission to hospital with ambulatory service dates. An example of an avoidable hospitalization is a hospitalization for asthma (ICD-9-CM = 493) that has no antecedent pharmacy claim for steroids.

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 Teicholz11  in 1990 and used by an Institute of Medicine report12  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 number of preventive visits was 0.2 visits/quarter for MAC-enrolled children compared with 0.1 visits/quarter for nonenrolled children. Although the mean number of ED visits was the same (0.06 visits/quarter) during the pre- and post-MAC periods, the mean number of ED visits for MAC-enrolled children was slightly higher than nonenrolled children (0.065 versus 0.057 visits per quarter).

Because multiple factors affect use, multivariate analysis was used to adjust for potential confounders. With all 3.2 million child-quarter observations included in the regression, MAC enrollment (odds ratio [OR] = 2.2, 95% confidence interval [CI] = 2.17–2.22) was strongly associated with the probability of any preventive care visits (1 or more). MAC enrollment was also associated with an increased probability of any ED use (OR = 1.4, 95% CI = 1.42–1.46) or any ambulatory care visit (OR = 2.58, 95% CI = 0.57–2.60).

Among those children who used ambulatory care (1.2 million child-quarters), MAC enrollment was associated with a lower probability of avoidable (OR = 0.89, 95% CI = 0.83–0.97) and any hospitalization (OR = 0.81, 95% CI = 0.79–0.84), but no change in ACS hospitalization (OR = 0.96, 95% CI = 0.92–1.01). With multiple hospitalizations per quarter excluded, MAC enrollment was associated with a reduced probability of avoidable (OR = 0.86, 95% CI = 0.80–0.93), ACS (OR = 0.93, 95% CI = 0.88–0.98), and any pediatric hospitalization (OR = 0.79, 95% CI = 0.76–0.81). The probability of an avoidable hospitalization was inversely related to the number of preventive care visits (OR = 0.70, 95% CI = 0.67–0.74) and directly related to ED visits (OR = 2.11, 95% CI = 2.06–2.16).

Conclusions. Enrollment in the MAC program and preventive care were associated with a reduced probability of avoidable as well as any pediatric hospitalization. Given the strong association between preventive care and reduced probability of hospitalization, it is likely that MAC exerts a positive effect on hospitalization through augmented preventive care, ie, numbers of preventive care visits, required EPSDT, increased access, and provider continuity. Further research is needed to document the clinical effectiveness of preventive care for children.

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