National probability samples in studies of low-prevalence diseases. Part I: Perspectives and lessons from the HIV cost and services utilization study.

OBJECTIVE: To examine the trade-offs inherent in selecting a sample design for a national study of care for an uncommon disease, and the adaptations, opportunities and costs associated with the choice of national probability sampling in a study of HIV/AIDS. SETTING: A consortium of public and private funders, research organizations, community advocates, and local providers assembled to design and execute the study. DESIGN: Data collected by providers or collected for administrative purposes are limited by selectivity and concerns about validity. In studies based on convenience sampling, generalizability is uncertain. Multistage probability sampling through households may not produce sufficient cases of diseases that are not highly prevalent. In such cases, an attractive alternative design is multistage probability sampling through sites of care, in which all persons in the reference population have some chance of random selection through their medical providers, and in which included subjects are selected with known probability. DATA COLLECTION AND PRINCIPAL FINDINGS: Multistage national probability sampling through providers supplies uniquely valuable information, but will not represent populations not receiving medical care and may not provide sufficient cases in subpopulations of interest. Factors contributing to the substantial cost of such a design include the need to develop a sampling frame, the problems associated with recruitment of providers and subjects through medical providers, the need for buy-in from persons affected by the disease and their medical practitioners, as well as the need for a high participation rate. Broad representation from the national community of scholars with relevant expertise is desirable. Special problems are associated with organization of the research effort, with instrument development, and with data analysis and dissemination in such a consortium. CONCLUSIONS: Multistage probability sampling through providers can provide unbiased, nationally representative data on persons receiving regular medical care for uncommon diseases and can improve our ability to accurately study care and its outcomes for diseases such as HIV/AIDS. However, substantial costs and special circumstances are associated with the implementation of such efforts.

Epidemiology of carotid endarterectomy among Medicare beneficiaries: 1985-1996 update.

BACKGROUND AND PURPOSE: This article describes changes in the rate and outcome of carotid endarterectomies among Medicare beneficiaries. METHODS: We analyzed International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes as shown on Medicare bills to calculate carotid endarterectomy frequency, rate, and perioperative mortality by patient demography and hospital characteristics. RESULTS: After initially peaking at 61273 procedures (20.6 per 10000 beneficiaries) in 1985, the frequency of carotid endarterectomy among Medicare beneficiaries declined to 46571 (14.3 per 10000) in 1989 and then rose to 108275 (28.6 per 10000) in 1996. Patients were predominantly aged 65 to 74 years, male, and white; surgery occurred mainly in large, urban, nonprofit, and teaching hospitals. Perioperative mortality declined from 3.0% in 1985 to 1.6% in 1996. CONCLUSIONS: The frequency and rate of carotid endarterectomy showed prompt response to reports from clinical trials. Perioperative mortality both improved and converged over time but did not attain the rates reported by the trials. Patients aged 85+ years suffered twice the average perioperative mortality.

Medications used for paediatric HIV infection in the USA, 1991-1992.

Medications constituted the third largest health care expenditure for children infected with the human immunodeficiency virus (HIV). Previous literature had not investigated volume or cost of pharmaceuticals consumed by individual patients. The US Agency for Health Care Policy & Research (AHCPR) therefore sponsored the AIDS Cost & Services Utilization Survey (ACSUS) to measure utilization of health care services, including medications. Starting in 1991, it surveyed 100 children with AIDS and 41 HIV-infected children (via adult proxies) six times at quarterly intervals and collected their outpatient bills. These children reported using 5,634 prescriptions and had 5,026 bills. Children with AIDS reported more prescriptions than HIV-infected children. On the basis of CD4 counts and age, 14.2% of children had indications for antiretrovirals, but did not receive them; and 17.7% warranted PCP prophylaxis but did not receive it. Outpatient bills averaged $2,325 and inpatient bills averaged $7,725 per year. These amounts projected nationally to $48.2 million annually, mostly paid by Medicaid.

Pediatric human immunodeficiency virus infection. Recent evidence on the utilization and costs of health services.

OBJECTIVE: To measure the utilization and costs of pediatric human immunodeficiency virus (HIV)-related health care services. DESIGN: Cohort survey. SETTING: Eight outpatient departments serving large numbers of HIV-infected children in five standard metropolitan areas with high prevalence of HIV-infected children. PATIENTS: One hundred forty-one HIV-seropositive children older than 15 months of age or children whose clinical conditions meet the definition of acquired immunodeficiency syndrome (AIDS) at any age who visited the selected providers during the second quarter of 1991. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Quarterly interview survey (via adult proxies) of health care services utilization during each preceding 3-month period, repeated six times between March 1991 and August 1992. Charge data were abstracted from inpatient, outpatient, home health care, and pharmacy bills. RESULTS: Children with AIDS averaged 1.4 hospitalizations, 16 inpatient days, two emergency department visits, 18 ambulatory care visits, 15 professional home health care visits, and one dental visit per year, generating an estimated $37,928 in annual charges. The HIV-infected children used fewer services, with annual charges of $9382. CONCLUSIONS: We found lower utilization than reported in prior research on pediatric HIV and similar unit costs after inflation adjustment. Increasing experience in clinical management and expanded ambulatory care may have contributed to reductions in inpatient services utilization and total costs since the mid-1980s.

Correlates of medical service utilization among people with HIV infection.

OBJECTIVE: To examine factors affecting the use of inpatient, outpatient, and emergency room services by people with HIV infection. DATA SOURCES AND STUDY SETTING: Study participants are adults with HIV infection receiving services at major providers of medical care in ten U.S. cities. Six interviews were conducted over an 18-month period (March 1991 to September 1992). DATA COLLECTION METHODS: Data on service utilization, personal background characteristics, insurance status, and functional status are based on self-report. Disease stage is based on medical record data. STUDY DESIGN: This is an observational study using a panel survey design. Linear and Poisson regression analyses were conducted to determine the effects of need, enabling, and predisposing factors on the dependent variables of ambulatory visits, emergency room visits, inpatient admissions, and average length of inpatient stay. Analyses use 1,449 respondents who completed the second and third interviews. Independent variables were measured as of the second interview, while dependent variables were measured in the third and fourth interview periods. PRINCIPAL FINDINGS: Service utilization was higher among respondents with AIDS than among those at earlier stages of HIV infection. Functional limitations, experienced pain, and negative mood each were associated with increased service use, over and above disease stage. Black respondents reported more hospital admissions and longer lengths of inpatient stays than white respondents. Lack of insurance was related to reduced service use. The effects of disease stage and functional limitations were reduced among people with public, compared to private, insurance. CONCLUSIONS: While disease stage affects use of medical care, the experience of adverse HIV-related conditions, such as pain or functional limitations, has an additional effect on service use. Persistent racial differences in utilization remain to be explained. Lack of insurance impedes use directly and also modifies the effects of disease stage and functioning.

AIDS treatment costs during the last months of life: evidence from the ACSUS.

OBJECTIVE: The volume and cost of services consumed by persons with AIDS (PWAs) during their last months of life are examined in this study. DATA SOURCES: This study utilizes data from the AIDS Costs and Service Utilization Survey (ACSUS). The ACSUS is the most comprehensive survey of medical services that are consumed by persons with HIV. STUDY DESIGN: This study is restricted to persons with AIDS who survived the fifth time period (an approximately three-month period in the early spring and summer of 1992). The types and costs of services consumed during the fifth time period by PWAs who did survive (609) and who did not survive (79) the sixth time period are compared. DATA COLLECTION: The ACSUS consists of six interviews over an 18-month period from Spring 1991 to Fall 1992. PRINCIPAL FINDINGS: Decedents were hospitalized more than four times as many days and experienced more than four times the number of home health visits as survivors. Both the average length of stay (19.3 days for decedents and 10.3 for survivors) and the frequency of hospitalization during the fifth time period (.70 for decedents and .28 for survivors) were higher for decedents than survivors. The levels of outpatient care (including emergency room care) and of prescription drug use were similar for decedents and survivors. CONCLUSIONS: This study shows that the cost of treating decedents is more than three times the cost of treating survivors.

Epidemiology of carotid endarterectomies among Medicare beneficiaries.

Extensive debates exist in the literature on the indications, effectiveness, and risks of carotid endarterectomy. However, no investigations analyze the procedure's epidemiology. Medicare paid for essentially all carotid endarterectomies on patients over 65 years old, more than two thirds of all such surgery. Accordingly, we identified all 1985 to 1989 Medicare bills for ICD-9-CM code 38.12. This report found an average annual decrease of 6.4% in the frequency of carotid endarterectomies. Higher proportions and incidence rates occurred among 65- to 79-year-old people, men, and whites. Larger, urban, and nonprofit hospitals performed the procedure more often. The number of hospitals performing this procedure has increased over time. Mortality rates within 30 days decreased from 3.0% of procedures in 1985 to 2.5% in 1989. Higher than average death rates occurred among older, male, and black patients, and in low volume hospitals. Clinical trials undertaken in large, urban, teaching, high-volume institutions reported only 1% deaths. The institutions actually performing carotid endarterectomies differ from the clinical trials in their demography and perioperative mortality rates. This difference in community practice may limit the applicability of the clinical trials.

Diagnosis related group coding accuracy of the peer review organizations.

Congress created the peer review organizations (PROs), in part, to check the accuracy of diagnosis related groups (DRGs) billed to Medicare. This study determined the accuracy of the peer review organizations' abstraction of DRGs during federal fiscal year 1985. A two-stage cluster design sampled 7050 medical records from 239 hospitals stratified by size. Credentialed medical record professionals used blinded techniques with reliability checks to abstract the ICD-9-CM codes and select the correct DRGs. Physicians reviewed medical records whose abstracted DRG differed from the DRG paid by the fiscal intermediary. The peer review organizations reported abstracting 1715 of these discharges. The peer review organization selected the correct DRG in 75.6 percent of the 1715 abstractions, a significantly lower proportion than the 80.3 percent paid accurately by the fiscal intermediaries. Upcoding compounded the peer review organizations' errors.

Medicare reimbursement accuracy under the prospective payment system, 1985 to 1988.

BACKGROUND: Hospital reimbursement by Medicare's prospective payment system depends on accurate identification and coding of inpatients' diagnoses and procedures using the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). A previous study showed that 20.8% +/- 0.5% (mean +/- SE) of hospital bills for 1985 contained errors that changed their diagnosis related group (DRG) and that a significant 61.6% +/- 1.3% of errors overreimbursed the hospitals. This DRG "creep" improperly increased net reimbursement by 1.9%, +308 million when projected nationally. The present study updated our previous study with 1988 data. METHODS: The Office of Inspector General, US Department of Health and Human Services, obtained a simple random sample of 2451 hospital charts for Medicare discharges from 1988. The American Medical Record Association reabstracted the ICD-9-CM codes on a blinded basis, grouped them to DRGs, and determined the reasons for discrepancies. RESULTS: Coding errors declined to 14.7% +/- 0.7% in 1988, and a nonsignificant 50.7% +/- 2.6% of DRG errors overreimbursed the hospitals. Projected nationally, hospitals did not receive a significant overreimbursement. Physician misspecification of the narrative diagnoses underreimbursed the hospitals, while billing department resequencing overreimbursed them. CONCLUSIONS: The attestation requirement may have deterred DRG creep due to attending physician upcoding, but the peer review organizations' sentinel effect and educational activities have not eliminated hospital resequencing.

The accuracy of Medicare's hospital claims data: progress has been made, but problems remain.

BACKGROUND: Health care databases provide a widely used source of data for health care research, but their accuracy remains uncertain. We analyzed data from the 1985 National DRG Validation Study, which carefully reabstracted and reassigned ICD-9-CM diagnosis and procedure codes from a national sample of 7050 medical records, to determine whether coding accuracy had improved since the Institute of Medicine studies of the 1970s and to assess the current coding accuracy of specific diagnoses and procedures. METHODS: We defined agreement as the proportion of all reabstracted records that had the same principal diagnosis or procedure coded on both the original (hospital) record and on the reabstracted record. We also evaluated coding accuracy in 1985 using the concepts of diagnostic test evaluation. RESULTS: Overall, the percentage of agreement between the principal diagnosis on the reabstracted record and the original hospital record, when analyzed at the third digit, improved from 73.2% in 1977 to 78.2% in 1985. However, analysis of the 1985 data demonstrated that the accuracy of diagnosis and procedure coding varies substantially across conditions. CONCLUSIONS: Although some diagnoses and all major surgical procedures that we examined were accurately coded, the variability in the accuracy of diagnosis coding poses a problem that must be overcome if claims-based research is to achieve its full potential.

Good quality care increases hospital profits under prospective payment.

This study shows that, contrary to popular belief, the prospective payment system discourages skimping on medically indicated care. The quality of care on a nationally representative sample of Medicare discharges underwent judgmental review using implicit criteria. The reviewing physicians identified hospitalizations that omitted medically indicated services and diagnoses overlooked because of this skimping. After deduction for the cost of the omitted services and probability of negative diagnostic tests, good quality care would have increased hospital profits a significant 7.9 percent. As the specificity of diagnosis and intensity of treatment increase, the DRG payment rises faster than the cost of providing medically indicated services.

Qui tam: suing physicians who make false claims.

The 1986 False Claims Act Amendments authorize private citizens to sue on behalf of the U.S. government to recover federal funds from fraudulent recipients. The "relator" receives a share of any proceeds from a successful lawsuit. Originally enacted because of defense procurement scandals, this statute also applies to federal payments for health care (for example, Medicare, Medicaid, Civilian Health and Medical Program for Uniformed Services payments; veterans benefits; and research grants). Physicians can expect qui tam litigation to increase in the future.

Accuracy of Medicare reimbursement for cardiac arrest.

Diagnosis related group (DRG) 129 consists exclusively of discharges having a principal diagnosis of International Classification of Diseases, Ninth Revision, Clinical Modification code 427.5 (cardiac arrest). It excludes patients with more specific diagnoses (eg, myocardial infarction and arrhythmia) or patients admitted for a different reason and who subsequently experience cardiac arrest. This study used a one-stage sample design to select all DRG 129 discharges from random hospitals, stratified by their annual number of DRG 129 bills. Using blinded techniques, medical records specialists reabstracted the International Classification of Diseases codes for 857 medical records. For the bills that were not coded DRG 129 on reabstraction, physicians classified the incorrect bills by clinical situation and reason for error. Diagnosis related group 129 had significantly higher rates of coding errors and upcoding than other DRGs. Of discharges erroneously billed to DRG 129, 42.1% of the patients entered the hospital for heart disease other than cardiac arrest and 55.2% died after entering the hospital for other diseases. Attending physicians need to distinguish between the "immediate cause" of death for the death certificate and the "principal diagnosis" for reimbursement purposes.

Accuracy of diagnostic coding for Medicare patients under the prospective-payment system.

Reimbursement of hospitals by Medicare under the prospective-payment system is based on patients' diagnoses as coded at discharge. During the period October 1984 through March 1985, we studied the accuracy of the coding for diagnosis-related groups (DRGs) in hospitals receiving Medicare reimbursement. We used a two-stage cluster method to sample 7050 medical records from 239 hospitals that were stratified according to size. Using blinded techniques with reliability checks, medical-record specialists reabstracted the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes to assign correct DRGs to discharged patients. The correct DRGs were then compared with those originally assigned by the physician and the hospital administration. The study revealed an error rate of 20.8 percent in DRG coding. Errors were distributed equally between physicians and hospitals. Small hospitals had significantly higher error rates. Previous studies had found that errors occurred randomly, so that half the errors benefited the hospital financially and half penalized the hospital. The present study found that a statistically significant 61.7 percent of coding errors favored the hospital. These errors caused the average hospital's case-mix index--a measure of the complexity of illness of the hospital's patients--to increase by 1.9 percent. As a result, hospitals received higher net reimbursement from Medicare than was supportable by the medical records. We conclude that "creep" does occur in the coding of DRGs, resulting in overpayment to hospitals for patients covered by Medicare.

Determination of energy change associated with dissolution of a solid.

The dissolution of a solid immersed in a solvent was considered as a consecutive process, consisting of a primary surface interaction leading to the production of a new surface at the solid-liquid interface, solvation of the solid at the interface, and transfer of the solvated solid into the bulk of the solution. The energy changes involved in each step were studied for the dissolution of m-tolylacetamide in hexane and heptane. An energy diagram was constructed according to the proposed dissolution mechanism. The heats of dissolution determined from the energy diagram agreed well with those obtained experimentally.