Admissions For Ambulatory Care Sensitive Conditions Research Articles

Primary Care Physician Supply and Children's Health Care Use, Access, and Outcomes: Findings From Canada

To describe the relationship of primary care physician (PCP) supply for children and measures of health care access, use, and outcomes. We conducted a population-based, cross-sectional study of all Ontario children from 2003 to 2005. We used health administrative data to calculate county-level supply (full-time equivalents [FTEs]) of PCPs. We modeled the relationship of supply to (1) recommended primary care visits, (2) emergency department (ED) use, and (3) ambulatory care-sensitive condition admissions and adjusted for neighborhood income. We used population-based surveys to describe access. The county-level PCP supply ranged from 1720 to 4720 children per FTE. Of the children, 45.4% live in the highest-supply areas (<2000 children per FTE) and 8% in the lowest-supply areas (>3000 children per FTE). Compared with high-supply counties, the lowest had significantly lower rates of primary care visits (2716 vs 7490 per 1000) and higher proportions of newborns without early follow-care (58.2% vs 14.5%). Low-supply areas had higher rates of ED visits (440 vs 179 per 1000) and admissions. A stepwise gradient existed for every decrease in supply for most measures. Self-reported access barriers were most evident in areas with >3500 children per FTE (32.8% without a physician). Under universal insurance there are differences in access to, and outcomes of, primary care related to local physician supply after controlling for neighborhood income. The most pronounced effect is on primary and ED care use, but there are implications for acute and chronic disease control. Physician distribution is a critical issue to address in policies to improve access to care.

Racial Disparities in Hospitalizations for Ambulatory Care–Sensitive Conditions

Variation in the quality of ambulatory care may be a key factor in explaining disparities in health, and these disparities have large cost implications. This study identified differences in hospitalization rates for elderly African-American and white Marylanders for eight ambulatory care-sensitive conditions (ACSCs). It assessed the relative contribution of race to disparities in preventable hospitalizations after controlling for demographic and socioeconomic factors as well as underlying prevalence. It also estimated the excess cost associated with these disparities. Using prevention quality indicator specifications from the Agency for Healthcare and Research Quality applied to 2006 Medicare claims data, eight ACSC hospitalization measures were developed for 569,896 Maryland Medicare beneficiaries. The analysis was conducted in 2008. A Poisson regression model identified race, age, gender, and income as factors associated with differences in ACSC hospitalization rates. Excess costs were estimated from excess hospitalizations of African Americans and the median cost per admission. African Americans had significantly higher rates of ACSC hospitalizations than whites for five of eight conditions after controlling for demographic, socioeconomic, and geographic factors. Excess costs from disparities in quality ranged from $8 million (heart failure) to $38,000 (urinary tract infection). Race may be a key predictor of preventable hospitalizations for some ACSCs. Racial disparities in these hospitalizations represent excess costs to Medicare. Because ACSC admissions are potentially preventable with optimal ambulatory care, improving care for minority populations may reduce disparities and lower hospital costs.

Continuity of diabetes care is associated with avoidable hospitalizations: evidence from Taiwan's National Health Insurance scheme

Taiwan's health-care system allows patients to utilize specialty services without referrals by primary care providers. This discontinuity of care may lead to increases in future hospitalizations. This study aims to determine whether the discontinuity of care is associated with the risk of hospitalization. A secondary data analysis based on a claim data of a nationally representative random sample of diabetic patients in Taiwan. A usual provider continuity (UPC) index was developed-a ratio of the visits to the physician that subjects most usually see relevant to diabetes care to the total physician visits relevant to diabetes care-to investigate its association with the risk of hospitalization. Taiwan's National Health Insurance scheme from 1997 through 2002. Totally 6476 diabetic patients. INTERVENTION(s) None. MAIN OUTCOME MEASURE(s) Diabetes-related short-term and long-term ambulatory care sensitive condition (ACSC) admissions. Patients with ACSC admissions had significantly lower UPC scores compared with those without ACSC admissions. Using a Cox regression model that controlling for age, sex, severity of diabetes and the number of total visits, patients with low to medium continuity of care (UPC <0.75) were found to be significantly associated with increased risk of hospitalization as compared with patients with high continuity of care, especially for long-term ACSC admissions (relative risk: 1.336 [1.019-1.751]). Higher continuity of care with usual providers for diabetic care is significantly associated with lower risk of future hospitalization for long-term diabetic complication admissions. To avoid future hospitalization, health policy stakeholders are encouraged to improve the continuity of care through strengthening the provider-patient relationships.

Prioritizing ambulatory care sensitive hospital admissions in England for research and intervention: a Delphi exercise

AimThe aim of this study was to prioritize hospital admissions for ambulatory care sensitive conditions (ACSCs) and interventions for future research and implementation.BackgroundInitiatives aimed at reducing hospital admission need to be targeted at those patients who could avoid admission to hospital, either by prevention, earlier detection and treatment, or by the provision of alternative types of care. Admissions for ACSCs should ideally be prevented by care provided outside hospital.MethodsThe study used a modified Delphi method to elicit the views of an expert panel. The Delphi process comprised two rounds and used a Web-based questionnaire. Participants were purposively sampled and comprised primary and community care clinicians, emergency clinicians and commissioning managers. Quantitative data were analysed to produce descriptive statistics. Qualitative data were analysed using content analysis.FindingsA total of 36 participants responded to both rounds of the Delphi survey. The condition given top priority was dementia, not currently a widely recognized ACSC or a national priority. The proportion of admissions that could be avoided by provision of care outside hospital was the most important factor in deciding which conditions to prioritize. Access to rapid response nursing and social care at home, intermediate care beds and mental health crisis teams were identified as key interventions to reduce admissions. Analysis of qualitative data showed several themes underlying clinical decisions to admit potentially avoidable admissions.In conclusion, the conditions selected by the panel for prioritization showed some concordance with the National Health Services’ priorities in this area; but the condition given top priority by the panel – dementia – is not currently a national priority. The panel showed a high degree of consensus around interventions that might lower the rate of avoidable admissions. The highest rated interventions involve the direct delivery of rapid access care in the community.

Hospitalization for Ambulatory-care-sensitive Conditions in Taiwan Following the SARS Outbreak: A Population-based Interrupted Time Series Study

Background/PurposeIn 2003, the severe acute respiratory syndrome (SARS) outbreak resulted in 8096 probable cases and 774 deaths in 26 countries. The purpose of this study was to explore the effect of the SARS outbreak on hospitalization for chronic ambulatory-care-sensitive conditions (ACSCs) in Taiwan.MethodsWe applied a population-based interrupted time series study design and used the time series auto-regressive integrated moving-average model to compare the actual and predicted admission rates of seven selected chronic ACSCs. The analyses were based on National Health Insurance hospital inpatient claims data from 1997 to 2003.ResultsThe impact of SARS on ACSCs after the outbreak varied among seven selected chronic conditions. Hospitalization for respiratory conditions was significantly lower than the predicted values, whereas hospitalization for diabetes was significantly higher than the predicted values after the outbreak.ConclusionAdmission rates for most ACSCs, except for diabetes, did not change in the post-SARS period. The reductions in outpatient utilization during the SARS outbreak did not appear to affect adversely admissions for most ACSCs.

Transportation Brokerage Services and Medicaid Beneficiaries' Access to Care

To examine the effect of capitated transportation brokerage services on Medicaid beneficiaries' access to care and expenditures. The study period from 1996 to 1999 corresponds to the period of a natural experiment during which Georgia and Kentucky implemented transportation brokerage services. Effects were estimated for asthmatic children and diabetic adults. We used difference-in-differences models to assess the effects of transportation brokerage services on access to care, measured by Medicaid expenditures and health services use. The study design is strengthened by the staggered implementation dates between states and within each state. For asthmatic children, transportation brokerage services increased nonemergency transportation expenditures and the likelihood of using any services; reductions in monthly expenditures more than offsetting the increased transportation costs. For diabetic adults, nonemergency transportation costs decreased despite increased monthly use of health services; average monthly medical expenditures and the likelihood of hospital admission for an ambulatory care-sensitive condition (ACSC) also decreased. The shift to transportation brokerage services improved access to care among Medicaid beneficiaries and decreased the expenditures. The increase in access combined with reduced hospitalizations for asthmatic children and ACSC admissions for diabetic adults are suggestive of improvements in health outcomes.

Hospitalizações entre crianças e adolescentes no território de abrangência de um serviço de Atenção Primária à saúde

A hospitalização, além de sofrimento familiar importante, é um evento de custo elevado para o sistema de saúde; além disso, ela pode ser, muitas vezes, prevenida no nível ambulatorial. Oobjetivo deste estudo foi identificar o percentual de hospitalizações por condições sensíveis à atenção ambulatorial (CSAA) que se referem àquelas em que a atenção efetiva e a tempo podem evitar internação. Foram estudadas 3.329 hospitalizações em menores de 19 anos, ocorridas nos anos de 2001 a 2004, em quatro hospitais do SUS, principais referências para uma população de áreas adscritas de um serviço de Atenção Primária em Saúde (APS). Análises univariadas e multivariadas foram empregadas para verificar associação entre variáveis independentes e a ocorrência de hospitalizações por CSAA. Identificou-se uma taxa anual de hospitalização de 2,9%. As doenças do aparelho respiratório são o grupo de causa mais freqüente (36%), seguido do grupo das perinatais (14%), infecciosas e parasitárias (10%), do aparelho digestivo (9%) e das causas externas (6%). As reinternações corresponderam a 16% do total de internações. A taxa de hospitalização por CSAA foi de 35,6%, variando de 25% a 43% entre as Unidades de APS. As variáveis relacionadas à maior ocorrência de hospitalizações por este motivo foram: idade de um a quatro anos (p&lt;0,01), ter ido direto para o hospital porque a Unidade estava fechada (p=0,04) ou pela gravidade do caso (p=0,03). O estudo indica a necessidade de incrementar ações de vigilância às hospitalizações por CSAA, que ocorrem com maior freqüência nos meses de inverno, às crianças de um a nove anos, por apresentarem-se mais vulneráveis à hospitalização por essas condições, e às reinternações, não reduzidas nos últimos quatro anos.

Rates of Preventable Hospitalization for Ambulatory Care Sensitive Conditions (ACSCs) among Patients with Lymphoid Malignancies (LM)

BACKGROUND: The influence of comorbid medical illness on treatment outcome and survival from LM has been well-characterized. Recent reports suggest that optimal management of these comorbidities may also be important. We sought to indirectly determine the effectiveness of outpatient treatment for ACSCs, conditions where good outpatient care can potentially prevent the need for hospitalization, by calculating population-based estimates of hospital admission rates among patients with LM. Methods: Data were obtained from the 2005 Nationwide Inpatient Sample. Using ICD-9CM codes, we identified all adult (age ≥20) admissions to U.S. community hospitals for LM (Hodgkin’s disease, non-Hodgkin’s lymphoma, and multiple myeloma). A comparator group without known diagnosis of cancer was created by excluding records containing any diagnosis code for malignant neoplasm or diagnosis/procedure code for cancer treatment. ACSC admissions, including those for short- and long-term complications of diabetes mellitus (DM), uncontrolled DM, asthma, hypertension (HTN), congestive heart failure (CHF), angina, and hypovolemia, were ascertained using algorithms developed and validated for the U.S. Agency for Health Care Research Quality Prevention Quality Indicators. The 2005 5-year prevalence for LM was obtained from SEER and used as the denominator for rate calculations in that group. A denominator for the no cancer group was created using U.S. Census estimates for the 2005 adult population less the SEER 5-year prevalence for all sites. Mean hospital charges were extracted for each admission and transformed into costs using Medicare cost-to-charge ratios. Length of stay, total costs, and in-hospital mortality were compared across groups for each ACSC. All means and proportions were sample weighted. Results: In 2005 there were an estimated 510,300 total LM admissions and 26,700,000 total admissions in the no cancer comparator group. Estimated hospitalization rates for each ASCS and odds ratios for the between group comparisons are detailed below. ACSC Group Admission Rate LM (per 100,000 pop) Admission Rate No Cancer (per 100,000 pop) OR (95% CI) DM Short-term Comp 74.7 33.3 2.25 (1.96–2.57) DM Long-term Comp 286.8 138.6 2.07 (1.93–2.22) DM Uncontrolled 50.4 12.06 4.18 (3.54–4.93) CHF 2360.0 465.5 5.17 (5.04–5.30) HTN 69.3 57.7 1.20 (1.04–1.38) Angina 60.0 21.9 2.74 (2.36–3.20) Asthma 255.4 81.5 3.14 (2.91–3.38) Hypovolemia 1086.5 90.1 12.2 (11.75–12.63) In-hospital mortality did not significantly differ between groups for any ACSC. Mean length of stay and hospital costs were likewise similar with the exception of costs for CHF ($8,957[95%CI 8,260–9,654] v. $7,176 [6,185–8,168]) and length of stay (5.6d [95%CI 4.8–6.3] v. 4.0d [3.9–4.1]) and costs ($8,702 [6,832–10,572] v. $5690[5,373–6,007]) for asthma admissions. Conclusions: Hospitalization of LM patients for ASCSs is common and occurs with odds generally &gt;2 times higher than among patients without a cancer diagnosis. Future studies should be conducted to determine factors influencing these findings (e.g. rates of comorbidity, influence of cancer treatment, utilization of primary care services) and to develop potential strategies for preventing hospital admissions.

Racially Disproportionate Admission Rates for Ambulatory Care Sensitive Conditions in North Carolina

This study examines race variations in quality of care through the proxy of ambulatory care sensitive (ACS) conditions. Hospital admission rates for eight ACS conditions were examined for African American and white Medicare beneficiaries in North Carolina. Temporal variations for ACS were also examined. Enrollment and inpatient claims files from the Centers for Medicare and Medicaid Services (CMS) for a 1999-2002 cohort who were aged 65 years or older in 1999 were examined. Descriptive statistics were computed for each year. Cochran-Mantel Haenszel tests were performed to assess differences in the admission rates for both individual and aggregate ACS conditions controlling for time. The Cochran-Armitage test for trend was used to evaluate changes in admission rates over time. African Americans had higher admission rates for five of the eight ACS conditions. The highest rates were for diabetes among African Americans (odds ratio [OR] = 2.86; 95% confidence interval [CI] [2.73, 2.99]) and adult asthma (OR = 1.51; 95% CI [1.43, 1.61]). African Americans tended to have lower ACS admission rates than white patients for chronic obstructive pulmonary disease (OR = 0.67; 95% CI [0.65, 0.69]); bacterial pneumonia (OR = 0.86; 95% CI [0.84, 0.89]), and angina (OR = 0.90; 95% CI [0.84, 0.97]). Using the ACS proxy for quality of health care as applied to examining race and ethnicity is a promising approach, though challenges remain. Admissions for ACS conditions between African American and white patients differ, but it is unclear why. This exploratory study must lead to an examination of social, economic, historical, and cultural factors for preventive, remedial, and beneficial policy initiatives.

The Concept and Usefulness of Ambulatory Care Sensitive Conditions as Indicators of Quality and Access to Primary Health Care

The purpose of this review is to introduce health services researchers, especially in the area of primary health care, to the meaning and concept of ambulatory care sensitive conditions (ACSCs). More specifically, this review explores the validity of ACSC admissions as proxy indicators of access to primary health care, provides a description of the factors that cause variations in ACSC admission rates, and presents a discussion of the potential usefulness and policy implications of these indicators for primary health care. Critical Interpretive Synthesis (CIS) methodology was used to review the literature on ACSC admissions indicators. Medline and Australasian Medical Index were searched for English language articles published between 1970 and August 2005. The results were supplemented by an internet search of the World Wide Web, further augmented by manual scans of material from deeper levels within the sites. Main finding from the review indicates that ACSC admissions are valid proxy indicators of access to primary health care. Socioeconomic factors are most important in explaining variations in ACSC admissions. Several uses and policy implications of ACSC admission indicators are discussed, including their potential for identifying gaps in the primary health care system and providing opportunities for targeted public health and health services interventions.

Spatial analysis of elderly access to primary care services

BackgroundAdmissions for Ambulatory Care Sensitive Conditions (ACSCs) are considered preventable admissions, because they are unlikely to occur when good preventive health care is received. Thus, high rates of admissions for ACSCs among the elderly (persons aged 65 or above who qualify for Medicare health insurance) are signals of poor preventive care utilization. The relevant geographic market to use in studying these admission rates is the primary care physician market. Our conceptual model assumes that local market conditions serving as interventions along the pathways to preventive care services utilization can impact ACSC admission rates.ResultsWe examine the relationships between market-level supply and demand factors on market-level rates of ACSC admissions among the elderly residing in the U.S. in the late 1990s. Using 6,475 natural markets in the mainland U.S. defined by The Health Resources and Services Administration's Primary Care Service Area Project, spatial regression is used to estimate the model, controlling for disease severity using detailed information from Medicare claims files. Our evidence suggests that elderly living in impoverished rural areas or in sprawling suburban places are about equally more likely to be admitted for ACSCs. Greater availability of physicians does not seem to matter, but greater prevalence of non-physician clinicians and international medical graduates, relative to U.S. medical graduates, does seem to reduce ACSC admissions, especially in poor rural areas.ConclusionThe relative importance of non-physician clinicians and international medical graduates in providing primary care to the elderly in geographic areas of greatest need can inform the ongoing debate regarding whether there is an impending shortage of physicians in the United States. These findings support other authors who claim that the existing supply of physicians is perhaps adequate, however the distribution of them across the landscape may not be optimal. The finding that elderly who reside in sprawling urban areas have access impediments about equal to residents of poor rural communities is new, and demonstrates the value of conceptualizing and modelling impedance based on place and local context.

The Relationship Between SCHIP Enrollment and Hospitalizations for Ambulatory Care Sensitive Conditions in California

The State Children's Health Insurance Program (SCHIP) was implemented in 1998, providing new funds for states to cover uninsured children. This study examines the relationship between SCHIP implementation in California and hospitalizations for ambulatory care sensitive conditions (ACSCs), an indicator of primary care access and quality. We use administrative SCHIP enrollment records for urban California counties, linked with corresponding rates of hospitalization for seven ACSCs among children ages 1-18 for 1996-2000. Results from multivariate regression models indicate that increases of 1 percentage point in SCHIP enrollment are associated with reductions of 0.42 ACSC admissions per 100,000 children age 1-18 (p = 0.009). Models that use lagged effects of SCHIP enrollment indicate an even stronger relationship. These are population-level relationships, and translate to much larger effects on the specific population subset that enrolled in SCHIP. These results suggest a strong beneficial effect of SCHIP on primary care among the children covered.

The Impact of Medicaid Managed Care on Hospitalizations for Ambulatory Care Sensitive Conditions

To determine whether Medicaid managed care is associated with lower hospitalization rates for ambulatory care sensitive conditions than Medicaid fee-for-service. We also explored whether there was a differential effect of Medicaid managed care by patient's race or ethnicity on the hospitalization rates for ambulatory care sensitive conditions. Electronic hospital discharge abstracts for all California temporary assistance to needy families (TANF)-eligible Medicaid beneficiaries less than age 65 who were admitted to acute care hospitals in California between 1994 and 1999. We performed a cross-sectional comparison of average monthly rates of admission for ambulatory care-sensitive conditions among TANF-eligible Medicaid beneficiaries in fee-for-service, voluntary managed care, and mandatory managed care. We calculated monthly rates of ambulatory care-sensitive condition admission rates by counting admissions for specified conditions in hospital discharge files and dividing the monthly count of admissions by the size of the at-risk population derived from a separate monthly Medicaid eligibility file. We used multivariate Poisson regression to model monthly hospital admission rates for ambulatory care-sensitive conditions as a function of the Medicaid delivery model controlling for admission month, admission year, patient age, sex, race/ethnicity, and county of residence. The adjusted average monthly hospitalization rate for ambulatory care-sensitive conditions per 10,000 was 9.36 in fee-for-service, 6.40 in mandatory managed care, and 5.25 in voluntary managed care (p<.0001 for all pairwise comparisons). The difference in hospitalization rates for ambulatory care sensitive conditions in Medicaid fee-for-service versus managed care was significantly larger for patients from minority groups than for whites. Selection bias in voluntary Medicaid managed care programs exaggerates the differences between managed care and fee-for-service, but the 33 percent lower rate of hospitalizations for ambulatory care sensitive conditions found in mandatory managed care compared with fee-for-service suggests that Medicaid managed care is associated with a large reduction in hospital utilization, which likely reflects health benefits. The greater effect of Medicaid managed care for minority compared with white beneficiaries is consistent with other findings that suggest that managed care is associated with improvements in access to ambulatory care for those patients who have traditionally faced the greatest barriers to health care.

The Victorian ambulatory care sensitive conditions study: rural and urban perspectives.

Ambulatory Care Sensitive Conditions (ACSCs) are those for which hospitalisation is thought to be avoidable with the application of preventive care and early disease management, usually delivered in the ambulatory setting. This study presents detailed analyses of ACSCs as a measure of health outcome that might vary with access to primary health care in rural and urban regions of Victoria. The Victorian Admitted Episodes Dataset (VAED), and data from the Health Insurance Commission, Medical Labour Force Annual Survey, socio-economic indexes for areas, and accessibility/remoteness index of Australia were merged to identify individual and aggregate level predictors of urban/rural differentials of ACSCs. Estimates of odds ratios and 95% confidence intervals were based on random effect multi-level generalised linear models. After adjustment for age, sex, and severity of illness, significant predictors of higher admission rates of ACSCs within rural areas include lack of insurance, emergency admissions, higher degree of remoteness, lower population density, lower number of general practitioners/10,000 population by local government area (LGA), lower number of general practitioner visits per person by LGA, and areas with lower socio-economic status, education and occupation, and economic resources. This study suggests that lack of timely and effective care may have a significant impact on rates of admissions for ACSCs in rural areas of Victoria especially in lower socio-economic groups.

Hospitalization rates as indicators of access to primary care

Variations in hospitalization rates for selected conditions are being used as indicators of the effectiveness of primary care in small areas. Are these rates actually sensitive to problems in local primary care systems? This study examines the relationship between ambulatory care sensitive condition (ACSC) hospital admission rates and primary care resources and the economic conditions in primary care market areas in North Carolina in 1994. The data show a high degree of correlation between the rates and income but not primary care resources. The distribution of rates did agree with expert assessments of the location of places with poor access to health services. The data confirm that access to effective primary care reflected in lower rates of ACSC admissions is a function of more than the professional resources available in a market area. The solution to reducing disparities in health status may not lie within the health system.

La Atención Primaria de Salud y las hospitalizaciones por Ambulatory Care Sensitive Conditions en Cataluña

Ambulatory Care Sensitive Conditions (ACSC) are a set of selected codes of hospital discharge diagnosis intended to measure avoidable hospitalizations. Primary Health Care Services may avoid the hospitalizations due to ACSC by applying any of the following interventions, that are characteristics of this level of care: a) primary prevention; b) secondary prevention, and c) tertiary prevention and rehabilitation. Observational, cross-sectional pilot study on 248,174 hospital discharges, from a population of 2,248,704 inhabitants in 161 Basic Health Care Units (BHCU), recorded in the minimum basic set of hospital discharge data in Catalonia during 1996. The complete list of diagnostic codes of ACSC, identified in the literature search, has been used. Crude and age-standardised hospitalisation rates have been estimated. Standardised hospitalisation ratio (SHR) has been computed to compare hospitalisation rates between BHCU. To analyse the effect of variables associated with high ACSC admission rates, multivariate analysis has been carried out by means of Poisson's regression. Hospitalisation due to ACSC account for 13% of all hospitalizations and 16% of hospital stay days. Acute and chronic diseases of the lower respiratory tract are the first cause of hospitalisation at any age group (< 5, 15-64 and > or = 65 years). The most common diagnostic groups, for all ages are respiratory disorders (acute and chronic diseases of the lower respiratory tract and pneumonia) and urinary tract conditions (pyelonephritis/urinary tract infection). The so-called self-limited health problems (ear, nose and throat mild infections/infections of the upper respiratory tract, febrile convulsions in children and gastroenteritis) account for more than 10% of all hospitalizations by ACSC, 45% of which occur in children. The overall crude hospitalisation rate by ACSC is 146.9/10,000 inhabitants (range: 12.4/10,000-239.9/10,000). SHR ranges from 0.01 to 1.85. "Hospital admissions due to ACSC" is a valid indicator to assess global performance of Primary Health Care and it identifies a part of hospital activity that is amenable to be cared for at Primary Health Care level and therefore potentially avoidable.

The Meaning of Ambulatory Care Sensitive Admissions: Urban and Rural Perspectives

Ambulatory care sensitive admission rates have been proposed as measures of access to health care. To test this, admissions for ambulatory care sensitive conditions (ACSC) were analyzed by multiple linear regression. The percentage of population below 200 percent of the federally defined poverty level, the percentage of black people, and the number of primary care providers per 1,000 population were found to be positively associated with ACSC admissions. Population density was negatively associated with ACSC admissions. There was no association between the location of the ZIP code in a health professional shortage area and ACSC admissions. Proximity to the hospital was found to be positively associated with ACSC admissions but was examined only in the most rural ZIP code group. The significant independent variables and the direction of their effects were the same across all ZIP code groups. The analysis suggests that high ACSC admissions may be a reflection of deficits in one or more of the following areas: primary care availability, accessibility, or appropriateness. In-depth study is needed to determine the relative importance of these factors in a given geographical area. There also may be environmental and social factors external to the health care system that contribute to ACSC admissions. The findings suggest that ACSC should be used cautiously as a measure of primary care system needs, and in conjunction with other health, demographic, or service utilization data.