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.

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.

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.

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.

Reliability of the health hazard appraisal.

As part of a controlled clinical trial of Health Hazard Appraisal's (HHA) efficacy in stimulating risk reduction, the reliability of the HHA questionnaire was evaluated. Of 203 subjects, only 30 (15%) had no contradictions when comparing the responses of the follow-up with baseline questionnaire. Overall, there was an average of 1.6 contradictions per subject. Failure to control for reliability may account for apparent reduction of risk reported in previous studies of HHA.