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Center for Health Services Research in Primary Care and Department of Family and Community Medicine, University of California, Davis, Calif
CORRESPONDING AUTHOR Peter Franks, MD Center for Health Services Research in Primary Care, Department of Family and Community Medicine, University of California, Davis 4860 Y Street, Ste 2300 Sacramento, CA 95817 pfranks{at}ucdavis.edu
| ABSTRACT |
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METHODS We used claims data from an independent practitioner association (IPA)-style managed care organization in the Rochester, NY, metropolitan area from 1996 through 1999. Cross-sectional and panel analyses of up to 4 years of claims data were conducted, involving 335,547 adult patients assigned to the panels of 687 primary care physicians (internists and family physicians). Multivariate analyses, adjusting for age, sex, case mix, and socioeconomic status derived from ZIP codes, examined the relationship between the first year of health insurance and Papanicolaou tests, mammograms in women older than 40 years, physician use, avoidable hospitalization, and expenditures.
RESULTS After multivariate adjustment, the first year of insurance was associated with a higher risk of not getting a mammogram, a higher risk of avoidable hospitalization, greater likelihood of visiting a physician, and higher expenditures, especially for testing. There was no relationship, however, between Papanicolaou test compliance and year of enrollment.
CONCLUSIONS The findings suggest there might be adverse clinical and financial implications associated with changing insurance.
Key Words: Managed care programs/utilization insurance preventive health services health care costs continuity of patient care
| INTRODUCTION |
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Disenrollment can result in loss of continuity with a health care provider and consequent patient-perceived loss of quality of primary care.1 Literature about the effects of continuity is limited.2,59 Mostly observational studies suggest that continuity is associated with increased satisfaction.10,11 Continuity is also associated with a lower risk of hospitalization and emergency department use.1214 Continuity might be associated with improved health behaviors and prevention compliance.1518 There is some circularity in these observational studies, in that patients who prefer continuity might also be more compliant and satisfied with a long-term relationship with a provider. Forrest et al19 found that patients in a point-of-service plan who self-referred to a specialist had less continuity, preferred direct access, and reported problems with their primary care physician. Relatively few other studies, mostly dating from the 1970s, address the possible costs of continuity.2023 From a physicians perspective, increased continuity is associated with greater knowledge about patients, resulting in shorter consultations and less laboratory testing.24 In the only recent randomized trial of the effects of continuity, Wasson et al25 found that male veterans older than 55 years assigned to a continuity group had fewer emergency hospitalizations, shorter hospitalizations, and greater satisfaction than men in a discontinuity group.
The extent to which studies on continuity apply to discontinuity in health insurance is unknown. There are few systematic studies of the effects of insurance change. Some evidence suggests that patients delay follow-up from emergency department visits after changing, and particularly after losing, health insurance.26
As an approach to assessing the possible impact of changing insurance, we compared health care indicators for persons newly enrolled in a health plan with those in subsequent years of being insured in the same health plan. Health care indicators selected were those that could be reliably identified in a claims database. Based on the continuity literature, we hypothesized that persons in their first year would be less likely to be in compliance with preventive procedures and generate higher expenditures as a result of increased laboratory testing. We also hypothesized that persons in their first year in the health plan would have a higher risk of avoidable hospitalization, because they might have had less opportunity to obtain timely ambulatory care.
| METHODS |
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Variables
All variables were derived from the claims data: age, sex, avoidable hospitalization during the year, expenditures during the year, case mix, socioeconomic status derived from patient ZIP codes, and years of enrollment. Women were coded according to whether they had a Papanicolaou test each year, and women older than 40 years were coded according to whether they had a mammogram. All patients were coded according to whether they had any physician visit and whether they had a visit to their primary care physician. The first year of enrollment was defined as the first full year the patient appeared in the data set, excluding the first year of available data (1996, because no reliable flag was available in the data set to indicate whether the patient had been enrolled the previous year). Other variables are defined below.
Avoidable Hospitalization Conditions We used Weissman and Epsteins approach27 to classify hospitalizations as avoidable or not avoidable. Based on previous research,2729 6 medical conditions meet the criteria for avoidable hospitalization conditions that might benefit from timely specialist care: angina, congestive heart failure, hypertension, asthma, chronic obstructive pulmonary disease, and diabetes mellitus. Patients were classified according to whether they were admitted during each of the 4 years for any of the avoidable hospitalization conditions.
Expenditures Total expenditures per panel member per year for each member were calculated from the "allowed amount" variable in the claims files. The allowed amount is the sum of the amount paid, the co-payment, deductible, and amount withheld for the risk pool. The allowed amounts varied across providers, so we standardized prices using the claims data. We also standardized prices for all years to 1996 prices. For physician claims, the standardized prices were the average amounts allowed for each current procedural terminology (CPT-4)30 code and provider specialty. For inpatient hospital claims, the standardized price was the average of allowed amounts by diagnosis-related group. For all other claims, the standardized price was the average of amounts allowed by CPT-4 code, with separate facility and nonfacility categories. Total expenditures for each patient were defined as the sum of the standardized prices for all services listed on the patients claim for the calendar year. In addition to total expenditures, we separated expenditures for inpatient hospital claims, physician encounter claims, and diagnostic testing.
Socioeconomic Status A summary socioeconomic status indicator was derived for each patient based on 1990 census socioeconomic indicators for the patients ZIP code (215 ZIP codes represented). We have previously found, as have others, that measures of socioeconomic status based on ZIP codes are as useful indicators of the health-related effects of socioeconomic status as are smaller areas, such as block groups or individual measures.31,32 The indicators chosen were median household income, percentage white, percentage with at least a high school graduation level of education, and percentage white-collar workers. We used principal components analysis 33 to derive a single socioeconomic status factor explaining as much as possible of the variance in the indicators.
Case Mix Case-mix adjustment was based on the ambulatory care groups (ACG) system.34 We used the ambulatory diagnostic groups (ADGs) of the ACG system because we have found,35 as have Salem-Schatz et al,36 that ADGs explained more of the variation in resource use than the ACG indicators. Based on the diagnoses in the claims data accumulated by the patient each year, a dummy indicator was derived for each ADG.
Analyses
The analyses were conducted at the level of the patient. To account for the nesting of patients within year and within physician, the analyses were conducted using the generalized estimating equations approach,37 and an exchangeable working correlation structure for the nested observations was implemented using SUDAAN.38 All analyses were adjusted for patient age (mean age minus age), age squared, sex, and ZIP-codederived socioeconomic status. In addition, case-mix adjustment was used for analyses of avoidable hospitalization risk and expenditures. Year of enrollment (1 through 4) was included as a series of dummy variables, with year 4 as the reference year. Analyses were conducted with and without adjustment for year (1997 through 1999), which exhibited some collinearity with year of enrollment. The results were broadly similar, and reported results include adjustment for year. Logistic regression analyses were used for Papanicolaou testing, mammogram testing, avoidable hospitalization, any primary care physician visit, and any physician visit.
To better reflect the effect sizes of the associations of being newly insured with the dependent variables, the odds ratios obtained from the logistic regression analyses were transformed to relative risks, using the method of Zhang and Yu.39 Expenditures were transformed using logarithms to normalize their distributions and analyzed with ordinary linear regression. Retransformed results are reported as percent changes in costs associated with being newly insured compared with being insured for at least 4 years. The large number of covariates involved in analyses using the ADG case-mix adjustment, together with the large number of observations, precluded analyzing the entire data set. Thus, for analyses involving adjustment for ADGs, only 1 year of a possible 4 that each patient was enrolled was randomly selected once only for inclusion in the analysis.
| RESULTS |
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| DISCUSSION |
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The absence of effect for Papanicolaou tests contrasts with the effect for mammograms. It might be that Papanicolaou tests are a more established part of womens health care, a routine that they carry with them from one insurance status (or no insurance) to the next more easily than getting mammograms. Mammograms might require more encouragement from physicians and the managed care organization, encouragement that requires some time to yield benefits.
Consistent with our hypothesis, avoidable hospitalizations were associated with being new to the insurance plan. The results are also congruent with the observations of Burstin et al, 26 who found newly insured persons delayed follow-up after emergency department visits. Because avoidable hospitalizations are relatively rare events, they might be of limited use in monitoring the possible adverse effects of being in a new health insurance plan. Although avoidable hospitalizations have been proposed to be included in Health Plan Employer Data and Information Set as a measure to assess quality of care, there is controversy about its validity.41
The higher adjusted expenditures in newly insured patients might reflect either decreased efficiency of care delivery or appropriate catch-up in care, especially for those without previous health insurance. Because we could not distinguish between persons switching health plans and those not previously insured, we were unable to develop a reliable algorithm for the claims data that would allow distinction between these two possibilities. More detailed analyses, including primary data collection, are required to assess these hypotheses. The net effects per enrollee are probably underestimated, because the analyses included only those with some expenditures, and newly enrolled persons were also more likely to visit a physician and generate at least some expenditures. In addition, waiting periods for patients new to the insurance plan are likely to result in some deferred care.
This study has a number of limitations. First, while the use of these claims data reduce biases associated with self-report, they do not allow separation of those who are previously uninsured from those previously insured with a different health plan. Thus, for persons facing forced discontinuity as a result of changes in insurance coverage, one might expect the adverse effects to be reflected in unnecessary additional evaluations as patient and physician get to know each other. For persons newly acquiring insurance, the increased utilization might be appropriate and reflect catch-up care and investigations.
Second, we found significant sociodemographic and clinical differences between those enrolled in their first year compared with those enrolled in subsequent years. Although we adjusted for these differences, it is possible that other unmeasured confounders could explain the results.
Third, the findings could have the questionable generalizability. At the time of the study, the Rochester area was dominated by 2 managed care organizations, with very little penetration of the market by for-profit managed care organizations. There might be relatively little disruption in continuity, because many providers were involved in both managed care organizations.
Finally, a limited array of prevention measures and the only one indirect indicator of chronic disease management (avoidable hospitalization) were examined. It is plausible that disruption of care for chronic disease has the most profound adverse effect on health care.42
Despite these limitations, this study represents a step toward examining possible costs of changing insurance status. Depending on the measure examined, we observed adverse effects (less prevention, higher costs, more avoidable hospitalizations) that lasted up to 3 years from enrollment in the health plan. These findings are consistent with the observations of Hjortdahl that it took 1 to 5 years for the primary care physicians sense of medical responsibility for and knowledge about their patients to reach adequate levels also reflected in resource use.24,43 Together with studies showing decreased patient satisfaction with forced health plan switches,4 the findings suggest that there are likely pervasive adverse consequences of the frequent rebidding of insurance contracts by employers. Given the relative stability of the health care insurance market in Rochester, it is likely that these findings represent an underestimate of possible effects in more competitive insurance environments with more frequent insurance changes. Further analyses in these other settings are needed.
| ACKNOWLEDGMENTS |
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| FOOTNOTES |
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Received for publication September 11, 2002. Revision received December 9, 2002. Accepted for publication December 20, 2002.
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