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Prenatal care and HIV infection.

Recent use of zidovudine (ZDV) to reduce vertical transmission of HIV disease in newborns has demonstrated varied, but in some studies, dramatic results, with reports of reduction from approximately 8% to 25%. With this potential of efficacy in saving lives, knowledge of access to prenatal care for HIV-infected pregnant women is urgent. The current study used face-to-face and phone survey methods and employed a 77-item questionnaire to assess barriers to prenatal care in two groups of HIV-positive and HIV-negative women (n = 106). All participants had a child(ren) under 4 years of age and were currently enrolled in a primary care or family HIV clinic. Results showed that HIV-positive women had specific concerns regarding access of perinatal care that included disclosure and fear of anger from health care providers. Barriers such as transportation, insurance and child care, among others, were not predictive of the level of prenatal care received, but results may be biased by the small number of women who had not received adequate care and the general selection process from women who were currently attending clinics. A high level of prenatal care was recorded across both cohorts. Misconceptions about vertical transmission and ZDV efficacy were demonstrated, including that more than 80% of all participants stated there was a greater than 50% chance of a pregnant untreated HIV-positive woman transmitting the virus; the documented transmission rate for untreated birth mothers is 20% to 25%. In addition, HIV-negative women showed little knowledge about vertical transmission and the use of ZDV, putting this group at risk in the future. Better educational methods to more women about perinatal HIV transmission and ADV could be imperative in significantly improving reduction of vertical transmission.

Adult↗

Impact of abciximab versus tirofiban on hospital length of stay for PCI patients.

The purpose of this retrospective study was to examine in a naturalistic setting the effect of abciximab versus tirofiban on hospital length of stay for patients undergoing percutaneous coronary intervention (PCI). Retrospective data were obtained from HCIASach's Clinical Pathways Database on 5,560 PCI patients who were administered either abciximab or tirofiban. Multivariate analysis was used to control for a wide range of factors (GPIIb/IIIa selection, patient demographics, insurance provider, health conditions, admission information, and hospital characteristics) that may influence hospital length of stay. Estimation was conducted via a two-stage sample selection model. After controlling for high-risk indications and sources of selection bias, results indicate that receipt of abciximab was associated with significantly shorter lengths of hospital stays compared to tirofiban (1.01 fewer days; p < 0.001). In a subgroup analysis of patients having an acute myocardial infarction (AMI; n = 2,593), receipt of abciximab was also found to be associated with significantly shorter hospital stays compared to tirofiban (0.60 fewer days; p < 0.001). Results of this study indicate that patients who are administered abciximab versus tirofiban have significantly shorter hospital stays. This reduction in length of stay may imply potential cost offsets for PCI patients who receive abciximab.

Abciximab↗

Sex differences in patient acceptance of cardiac transplant candidacy.

BACKGROUND: The overwhelming majority of cardiac transplant recipients are men. This can be partially explained by the earlier age at which heart failure develops in men. However, an underrepresentation of women also may reflect physician referral or selection biases or differences in patients' access to or acceptance of heart transplantation. METHODS AND RESULTS: We investigated whether sex bias occurred in the transplant candidate selection process at a single cardiac transplant center. We prospectively evaluated 386 individuals < 70 years of age (295 men, 91 women) referred for management of moderate to severe heart failure and/or cardiac transplant evaluation. Age, race, sex, heart failure type, New York Heart Association class, left ventricular ejection fraction, peak exercise oxygen consumption, disease duration, resting hemodynamic measurements, comorbidity index score, health insurance coverage, and estimated household income were recorded. For patients not accepted for transplantation, the reason for rejection was also obtained. Univariable and multivariable (logistic regression) analyses were performed comparing men and women and patients accepted and those not accepted for cardiac transplantation. Female sex was independently associated with rejection for cardiac transplantation (odds ratio, 2.57; P = .01). However, the reason for rejection (odds ratio, 2.57; P = .01). However, the reason for rejection was more likely to be patient self-refusal for women than for men (29% versus 9%), and female sex was independently associated with patient self-refusal (odds ratio, 4.68; P = .003). When patients who refused transplant were reclassified as accepted for transplant, female sex was no longer associated with nonacceptance. However, lower patient income was associated with nonacceptance for transplant. CONCLUSIONS: We found no evidence of sex bias in the selection of cardiac transplant recipients at our center. These findings suggest that the underrepresentation of women among cardiac transplant recipients may result, in part, from a sex difference in treatment preference, with a decreased willingness of women to undergo transplantation. The reasons for the difference in acceptance rates between men and women need to be elucidated.

Female↗

Use of insurance claims databases to evaluate the outcomes of ophthalmic surgery.

This article reviews methodological issues in research using Medicare claims data and reviews how those issues affect the interpretation of study results. Although studies using Medicare claims data can improve our knowledge of surgical outcomes, the ability to infer that one type of surgery or one surgeon is better than another is limited by such factors as bias due to inaccurate record keeping, confounding of treatment effects by other covariates, effect modification due to factors associated with treatment, and selective loss of follow-up of patients. Five studies on the outcomes of cataract surgery and capsulotomy are reviewed, providing illustrations of methodological strengths and weaknesses of this type of research.

Aged↗

Medicare beneficiary decision making about health insurance. Implications for a voucher system.

A two-phase study involving focus group interviews and a survey of 2,016 Medicare beneficiaries was conducted to examine beneficiary decision making about health insurance under a hypothetical Medicare voucher program. Some of the major findings were that: beneficiaries lack important information about Medicare and health insurance in general; plans with physician restrictions, no restrictions on hospitals, and benefits for custodial long-term care at home or in nursing homes are most preferred when prices are roughly equal to actuarial costs; plan features often interact rather than combined additively to affect choices; price sensitivity is small in comparison with sensitivity to other plan features; price sensitivity is particularly small for plans with custodial long-term care benefits; Medicare would not experience substantial selection bias in a voluntary system containing a wide range of plans preferred by beneficiaries; physician-restricted plans would experience favorable selection; plans with long-term custodial care benefits would experience some adverse selection which might be handled by modest price adjustments in view of the relatively low price elasticity of preferences.

Community Participation↗

Which physicians limit their Medicaid participation, and why.

OBJECTIVE: This study identifies factors differentiating Medicaid participating physicians who accept all Medicaid patients from those limiting their Medicaid participation. DATA SOURCES: Data come from periodic telephone surveys of random samples of physicians conducted by the American Medical Association (AMA). STUDY DESIGN: Surveys conducted in 1990-1993 were pooled to form a sample of 4,188 Medicaid-participating office-based physicians. Respondents were classified as accepting all Medicaid patients or as limiting their Medicaid participation. Descriptive statistics are used to examine differences between these groups with respect to selected personal, practice, community, and reimbursement variables. Logistic regression analysis is used to identify factors associated with physicians accepting all Medicaid patients or limiting their Medicaid participation in some way. DATA COLLECTION METHODS: Survey data were supplemented with 1990 census data, 1990 AMA Physician Masterfile data, and 1989 data on physician payment levels. PRINCIPAL FINDINGS: Less than half of Medicaid-participating physicians and only about one-third of participating primary care physicians accept all Medicaid patients. Higher Medicaid fees are associated with physicians participating fully, but the marginal effects of changes in fees on the probability of physicians participating fully is small. CONCLUSIONS: Increases in Medicaid reimbursement aimed at primary care physicians or those in underserved areas may convert limited participants into full participants and, in so doing, improve the access of Medicaid eligibles to care. The increases in payment level needed to increase the proportion of physicians participating fully would be substantial, however, and may not be politically feasible.

Data Collection↗

Unbiased estimation of relative reproductive success of different groups: evaluation and correction of bias caused by parentage assignment errors.

Parentage assignment is widely applied to studies on mating systems, population dynamics and natural selection. However, little is known about the consequence of assignment errors, especially when some parents are not sampled. We investigated the effects of two types of error in parentage assignment, failing to assign a true parent (type A) and assigning an untrue parent (type B), on an estimate of the relative reproductive success (RRS) of two groups of parents. Employing a mathematical approach, we found that (i) when all parents are sampled, minimizing either type A or type B error insures the minimum bias on RRS, and (ii) when a large number of parents is not sampled, type B error substantially biases the estimated RRS towards one. Interestingly, however, (iii) when all parents were sampled and both error rates were moderately high, type A error biased the estimated RRS even more than type B error. We propose new methods to obtain an unbiased estimate of RRS and the number of offspring whose parents are not sampled (zW(z)), by correcting the error effects. Applying them to genotypic data from steelhead trout (Oncorhynchus mykiss), we illustrated how to estimate and control the assignment errors. In the data, we observed up to a 30% assignment error and a strong trade-off between the two types of error, depending on the stringency of the assignment decision criterion. We show that our methods can efficiently estimate an unbiased RRS and zW(z) regardless of assignment method, and how to maximize the statistical power to detect a difference in reproductive success between groups.

Animals↗

Barriers to clinical trials. Part III: Knowledge and attitudes of health care providers.

The role of clinical trials is becoming extremely important for our understanding of the effects of different therapeutic modalities of cancer treatment and the value of their interactions. Participation of patients in clinical trials remains disappointingly low, with less than 3% of the estimated 1.17 million patients with newly diagnosed cancers entering the studies. Several physician-based factors hinder accrual of patients--(1) lack of awareness of or access to clinical trials, (2) physician bias that the trial therapy is not as good as the "standard therapy" even though the standard therapy may provide a response rate of less than 20%, (3) physician's concern about losing patients to follow-up, (4) the complexity of the clinical trial(s), which requires excessive amount of time to discuss, implement, and follow-up the patient, (5) the lack of equitable compensation for the physician's time and effort, and (6) excessive costs of laboratory and radiologic tests that are not paid by the agency or group sponsoring the study, particularly in Phase I and II trials. These factors are confounded by the lack of institutional review boards in several community hospitals, associated with a complex and lengthy procedure to institute such a board. The article presents recent surveys dealing with attitudes and practices of health care providers toward clinical trials. The National Cancer Institute, the American Cancer Society, and other societies, groups, and agencies, including the health insurance industry, should continue to encourage and support clinical trials.

Attitude of Health Personnel↗

Clinical perceptions of the risk of vertebral artery dissection after cervical manipulation: the effect of referral bias.

BACKGROUND CONTEXT: The growing recognition of cervical manipulation as a treatment of neck pain and cervicogenic headaches has lead to increased interest in potential complications that may result from this treatment approach. Recent surveys have reported that many neurologists will encounter cases of vertebral artery dissection that occur at various times after cervical manipulation, whereas most practitioners of spinal manipulation are of the opinion that these events are extremely rare. We asked the question whether these differences in perception could be explained in part by referral or selection bias. PURPOSE: To assess the effect of referral bias on the differences in perceived incidence of vertebral artery dissection after cervical manipulation between neurologists and chiropractors in Canada. STUDY DESIGN: This study was a retrospective review of cases where neurological symptoms consistent with cerebrovascular ischemia were reported by chiropractors in Canada. METHODS: An analysis of data from a chiropractic malpractice insurance carrier (Canadian Chiropractic Protective Association [CCPA]) and results of a survey of chiropractors was performed to determine the likelihood that a vertebral artery dissection after cervical manipulation would be reported to practicing chiropractors. This was compared with the likelihood that a neurologist would be made aware of such a complication. RESULTS: For the 10-year period 1988 to 1997, there were 23 cases of vertebral artery dissection after cervical manipulation reported to the CCPA that represents 85% of practicing chiropractors in Canada. Based on the survey, an estimated 134,466,765 cervical manipulations were performed during this 10-year period. This gave a calculated rate of vertebral artery dissection after manipulation of 1:5,846,381 cervical manipulations. Based on the number of practicing chiropractors and neurologists during the period of this study, 1 of every 48 chiropractors and one of every two neurologists would have been made aware of a vascular complication from cervical manipulation that was reported to the CCPA during their practice lifetime. CONCLUSIONS: The perceived risk after cervical manipulation by chiropractors and neurologists is related to the probability that a practitioner will be made aware of such an incident. The difference in the number of chiropractors (approximately 3,840 in 1997) and neurologists (approximately 4,000 in 1997) in active practice and the fact that each patient who has a stroke after manipulation will likely be seen by only one chiropractor but by three or more neurologists partly explains the difference in experience and the perception of risk of these two professions. This selection or referral bias is important in shaping the clinical opinions of the various disciplines and distorts discussion on the true incidence of these complications of cervical manipulation. The nature of this study, however, describes the likelihood that a clinician will be made aware of such an event and cannot be interpreted as describing the actual risk of stroke after manipulation.

Bias↗

The biopsychosocial characteristics of people seeking treatment for obesity.

BACKGROUND: To determine prospectively the characteristics of obese patients allowed to select either a medically supervised weight-reduction treatment program or a surgical treatment program, both offered at the same location. METHODS: This was a cohort study at a university medical center where patients, who self-referred themselves for weight loss treatments, were introduced to two different programs before they were allowed to start either program. Four hundred forty-three patients with a mean body mass index (BMI) of 45.6 +/- 0.5 (85 men, 358 women) self-selected either a combined supplemented fast with behavior modification (DIET, n = 208) or gastric bypass surgery (SURG, n = 235). Three hundred forty of these patients had private insurance (PI,) and 103 were receiving Medicaid/Medicare (publicly funded, PF). Each patient completed a semistructured psychiatric interview, obesity questionnaire, Profile of Mood Status (POMS), Beck Depression Inventory (BDI), Minnesota Multiphasic Personality Inventory (MMPI), and Hollingshead Index. RESULTS: Three distinct groups of patients emerged on the basis of their insurance reimbursement patterns (employed versus disabled or indigent) and biopsychosocial factors. The disabled and/or indigent group receiving PF usually chose SURG (n = 89) because their insurance program covered it, but 14 disabled patients receiving Medicare chose DIET (together labeled the PF:DS group). The PI patients were divided into two groups: SURG (PI:S), n = 146, and DIET (PI: D), n = 194, respectively, based on their program selection. These three groups differed significantly in their biopsychosocial patterns. The PF:DS subjects appeared to have the strongest degree of biologic influence, followed by the PI:S and PI:D subjects. The pattern of social influences was consistent with the pattern of biologic influences and the selection bias created in forming the PF and PI groups. The pattern of psychologic influences, however, did not appear to follow the pattern of biologic and social influences. PF:DS had the strongest psychologic loading, but PI:D had a stronger degree of psychopathologic impairment than PI:S. CONCLUSIONS: The significant differences in the biopsychosocial characteristics of these three groups of obese patients need to be considered by policy-makers when they design and review treatment studies and decide what treatment programs should be offered in medical insurance programs.

Adult↗

Differences in drug treatment services based on profit status.

The goal of this article is to examine whether profit status affects the provision of seven "core" drug treatment services and nine "auxiliary" treatment services. Data on the type of services provided by 8,606 treatment providers obtained from the National Survey of Substance Abuse Treatment Services (N-SSATS) collected by the Substance Abuse and Mental Health Services Administration (SAMHSA) in 2000 were used for this study. The types of services offered by the providers were modeled to be a function of the drug treatment providers' (DTP) profit status, DTP organizational and financial characteristics, staff's characteristics, clients' characteristics, and regional variables. A total of 16 logistic regressions were estimated. For-profit DTPs were found to be more likely to offer only two core services and were less likely to offer eight auxiliary services. However, after correcting for sample selection bias many differences in the supply of services between for-profit and nonprofit providers disappeared.

Adolescent↗

Institutional variability in a minimal risk, population-based study: recognizing policy barriers to health services research.

OBJECTIVE: To describe (1) the institutional variability in study approval and willingness to obtain federal assurance documents for a federally supported, minimal risk health services research project conducted during the implementation of the Privacy Rule and federalwide assurances, and (2) the potential impact of such policy on selection of research subjects and generalizability of study results. DATA SOURCES: Primary data collection from 2001 to 2004. STUDY DESIGN: We provide a descriptive analysis of a prospective, observational, out-of-hospital study. STUDY SETTING: Twenty-seven pediatric receiving hospitals were approached for participation in a study validating a decision rule to identify seriously injured children involved in motor vehicle crashes in Los Angeles County. Two federal research policies, the Privacy Rule and the requirement for federalwide assurances, were implemented during the project. DATA COLLECTION: All 27 hospitals were sent an identical research protocol requesting approval to review charts of children transported to their facility. The research protocol included strict confidentiality protections, was noninterventional, did not alter the standard of care at the scene or at the hospital, and met requirements for waivers of both informed consent and the Health Insurance Portability and Accountability Act. Because the project was federally supported, all participating hospitals were required to have a federalwide assurance. The hospitals receiving the research protocol were the unit of analysis and outcomes included: approval of the research protocol, total number of days to study approval, and successfully obtaining a federalwide assurance. PRINCIPLE FINDINGS: Overall, 6 of 27 (22 percent) hospitals refused to participate in the study, all of which were community hospitals. The median time from submitting an application to study approval was 118 days (interquartile range 34-254, range 12-960 days) and time to study approval differed when hospitals were categorized by type and the presence of an institutional review board (p=.053). No institutional review resulted in a change in the basic study protocol, although one hospital required paramedic consent. Following intensive efforts to secure federalwide assurances, 12 of 27 hospitals (44 percent) possessed the necessary assurance to conduct the study. If all patients transported to hospitals that failed to obtain such an assurance were omitted, the sample size would have been reduced by 62 percent and would have excluded all children transported to community hospitals. CONCLUSIONS: There is substantial institutional variability in approval of a minimal risk observational study and in willingness to obtain a federalwide assurance, particularly among community hospitals. Federal research policy involving patient privacy and institutional assurances may be contributing to this variability, which can adversely affect selection of research subjects, disrupt population-based study design, and threaten the generalizability of study results.

Academic Medical Centers↗

Early ultrasound dating of pregnancy: selection and measurement biases.

Can using early ultrasound examinations to date pregnancy introduce information bias in perinatal research? Our purpose was to identify determinants of early ultrasound examinations and to compare early ultrasound to menstrual history dating. Between January 1987 and June 1989, 1159 white, largely middle class, prenatal patients were contacted for a prospective observational study. 876 (76%) agreed to participate. Of these 764 (87%) met the eligibility criteria for this analysis, namely singleton pregnancy, delivered after 20 weeks (spontaneous or induced, vaginal or c-section), with prenatal chart abstracted. Selection factors for early ultrasound identified in multivariate analysis were: bleeding in early pregnancy, OR = 1.9 (1.0, 3.5), attendance at health maintenance organization OR = 7.2 (3.4, 15), no insurance or Medicaid only OR = 0.3 (0.1, 0.6), and increasing time from last menstrual period to first prenatal visit in weeks OR = 0.89 (0.85, 0.93). In conformity with previous results, ultrasound dating of pregnancy led to a higher estimate of preterm delivery (10 vs 7.6%), a higher estimate of term delivery (87.2 vs 82.7%) and a lower estimate of postterm delivery (2.8 vs 9.7%) than dating by menstrual history, p < 0.001. Selection factors and measurement issues, such as those described here, could introduce bias and should be carefully considered in the design, analysis and interpretation of perinatal research.

Female↗

Criteria for selection of patients for bariatric surgery.

International criteria for bariatric surgery and bariatric surgeons have been well-defined in terms of the current state of the art and are presented together with weight tables and a list of co-morbidities of morbid obesity. The bariatric surgeon should make the primary judgement concerning bariatric surgery using these criteria as guidelines only, not strict rules; others who use these criteria should govern themselves in a like, fair-minded, fashion. Medical insurers' and their agents' criteria, if excessively restrictive relative to the guidelines, may reflect an ingrained prejudice against the morbidly obese, manifesting itself in an unfair, unethical and immoral bias. It is the essence of humane and equitable behaviour on the part of all concerned that the morbidly obese receive non-discriminatory, appropriate treatment, care and medical insurer coverage for their disease and its comorbidities.

Body Weight↗

The productivity of mental health care: an instrumental variable approach.

BACKGROUND: Like many other medical technologies and treatments, there is a lack of reliable evidence on treatment effectiveness of mental health care. Increasingly, data from non-experimental settings are being used to study the effect of treatment. However, as in a number of studies using non-experimental data, a simple regression of outcome on treatment shows a puzzling negative and significant impact of mental health care on the improvement of mental health status, even after including a large number of potential control variables. The central problem in interpreting evidence from real-world or non-experimental settings is, therefore, the potential "selection bias" problem in observational data set. In other words, the choice/quantity of mental health care may be correlated with other variables, particularly unobserved variables, that influence outcome and this may lead to a bias in the estimate of the effect of care in conventional models. AIMS OF THE STUDY: This paper addresses the issue of estimating treatment effects using an observational data set. The information in a mental health data set obtained from two waves of data in Puerto Rico is explored. The results using conventional models - in which the potential selection bias is not controlled - and that from instrumental variable (IV) models - which is what was proposed in this study to correct for the contaminated estimation from conventional models - are compared. METHODS: Treatment effectiveness is estimated in a production function framework. Effectiveness is measured as the improvement in mental health status. To control for the potential selection bias problem, IV approaches are employed. The essence of the IV method is to use one or more instruments, which are observable factors that influence treatment but do not directly affect patient outcomes, to isolate the effect of treatment variation that is independent of unobserved patient characteristics. The data used in this study are the first (1992-1993) and second (1993-1994) wave of the ongoing longitudinal study Mental Health Care Utilization Among Puerto Ricans, which includes information for an island-wide probability sample of over 3000 adults living in poor areas of Puerto Rico. The instrumental variables employed in this study are travel distance and health insurance sources. RESULTS: It is very noticeable that in this study, treatment effects were found to be negative in all conventional models (in some cases, highly significant). However, after the IV method was applied, the estimated marginal effects of treatment became positive. Sensitivity analysis partly supports this conclusion. According to the IV estimation results, treatment is productive for the group in most need of mental health care. However, estimations do not find strong enough evidence to demonstrate treatment effects on other groups with less or no need. The results in this paper also suggest an important impact of the following factors on the probability of improvement in mental health status: baseline mental health status, previous treatment, sex, marital status and education. DISCUSSION: The IV approach provides a practical way to reduce the selection bias due to the confounding of treatment with unmeasured variables. The limitation of this study is that the instruments explored did not perform well enough in some IV equations, therefore the predictive power remains questionable. The most challenging part of applying the IV approach is on finding "good" instruments which influence the choice/quantity of treatment yet do not introduce further bias by being directly correlated with treatment outcome. CONCLUSIONS: The results in this paper are supportive of the concerns on the credibility of evaluation results using observation data set when the endogeneity of the treatment variable is not controlled. Unobserved factors contribute to the downward bias in the conventional models. The IV approach is shown to be an appropriate method to reduce the selection bias for the group in most need for mental health care, which is also the group of most policy and treatment concern. IMPLICATIONS FOR HEALTH CARE PROVISION AND USE: The results of this work have implications for resource allocation in mental health care. Evidence is found that mental health care provided in Puerto Rico is productive, and is most helpful for persons in most need for mental health care. According to what estimated from the IV models, on the margin, receiving formal mental health care significantly increases the probability of obtaining a better mental health outcome by 19.2%, and one unit increase in formal treatment increased the probability of becoming healthier by 6.2% to 8.4%. Consistent with other mental health literature, an individual's baseline mental health status is found to be significantly related to the probability of improvement in mental health status: individuals with previous treatment history are less likely to improve. Among demographic factors included in the production function, being female, married, and high education were found to contribute to a higher probability of improvement. IMPLICATION FOR FURTHER RESEARCH: In order to provide accurate evidence of treatment effectiveness of medical technologies to support decision making, it is important that the selection bias be controlled as rigorously as possible when using information from a non-experimental setting. More data and a longer panel are also needed to provide more valid evidence. tion.

Journal Article↗

Potential impact of the HIPAA privacy rule on data collection in a registry of patients with acute coronary syndrome.

BACKGROUND: Implementation of the Health Insurance Portability and Accountability Act (HIPAA) Privacy Rule has the potential to affect data collection in outcomes research. METHODS: To examine the extent to which data collection may be affected by the HIPAA Privacy Rule, we used a quasi-experimental pretest-posttest study design to assess participation rates with informed consent in 2 cohorts of patients eligible for the University of Michigan Acute Coronary Syndrome registry. The pre-HIPAA period included telephone interviews conducted at 6 months that sought verbal informed consent from patients. In the post-HIPAA period, informed consent forms were mailed to ask for permission to call to conduct a telephone interview. The primary outcome measure was the percentage of patients who provided consent. Incremental costs associated with the post-HIPAA period were also assessed. RESULTS: The pre-HIPAA period included 1221 consecutive patients with acute coronary syndrome, and the post-HIPAA period included 967 patients. Consent for follow-up declined from 96.4% in the pre-HIPAA period to 34.0% in the post-HIPAA period (P<.01). In general, patients who returned written consent forms during the post-HIPAA period were older, were more likely to be married, and had lower mortality rates at 6 months. Incremental costs for complying with the HIPAA Privacy Rule were $8704.50 for the first year and $4558.50 annually thereafter. CONCLUSIONS: The HIPAA Privacy Rule significantly decreases the number of patients available for outcomes research and introduces selection bias in data collection for patient registries.

Acute Disease↗

Do HMOs make a difference? Data and methods.

This paper describes the common data source and methods used in this study. Data come from the Community Tracking Study Household Survey, a nationally representative survey of individuals conducted in 1996-1997. Focusing on the privately insured, nonelderly population, the study examines the effect of health maintenance organizations (HMOs) on access, service use, and consumer assessments, as well as how these effects differ across population subgroups. Multivariate models control for population characteristics and location differences between HMO and non-HMO enrollees. Tests for endogeneity of plan type (selection bias) indicated that this did not pose a threat to the analysis.

Adolescent↗