Coding of Acute Myocardial Infarction

Clinical and Policy Implications

Abstract

Study Objective: To evaluate the appropriateness of diagnostic coding of acute myocardial infarction across teaching and nonteaching hospitals.

Design: Retrospective review of a random sample of medical records to find evidence of the occurrence and active treatment of acute myocardial infarction during the admission. Setting: Five tertiary teaching, five other teaching, and five nonteaching hospitals in metropolitan Boston.

Cases: Random sample of hospital admissions assigned a discharge diagnosis of acute myocardial infarction between October 1984 and September 1985.

Measurement and Main Results: Of the 1003 cases reviewed, 260 did not meet the clinical criteria for acute myocardial infarction. At tertiary hospitals, 175 (41.7%) failed to qualify, compared with 25 (9.1%) at nonteaching facilities. In a large fraction of the disqualified cases, the patients had been admitted to exclude the diagnosis of acute myocardial infarction; although explicitly "ruled out," an acute myocardial infarction code was assigned. Sixty-six cases from teaching hospitals did not qualify because the patient had been admitted only for coronary angiography after an uneventful postmyocardial infarction course. Almost one-third of these patients had had their infarcts from 5 to 8 weeks before the angiography admission.

Conclusions: Cases with an inappropriate discharge diagnosis of acute myocardial infarction may be concentrated in teaching hospitals. This finding could have implications for Medicare's diagnosis-related group payment system and governmental and other research efforts that use these data for such purposes as drawing inferences about the quality of hospital care.

Article and Author Information

  • From the Boston University Medical Center, Boston, Massachusetts. For current author addresses, see end of text.

  • Grant Support: Partial support by a grant from the Health Care Financing Administration, Office of Research, under Cooperative Agreement #18-C-98856/1-02.

  • Current Author Addresses: Drs. Iezzoni and Moskowitz: Health Care Research Unit, Section of General Internal Medicine, Boston University School of Medicine, Boston, MA 02118.

    Ms. Sickles: Quality Assurance, and Dr. Levine: Section of Cardiology, University Hospital, Boston, MA 02118.

    Dr. Sawitz: Harvard Community Health Plan, 111 Grossman Drive, Braintree, MA 02184.

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