Outpatient diagnostic errors: unrecognized hyperglycemia.

Context: To estimate the prevalence of unrecognized diabetes in a large managed care organization (MCO).

Design: Retrospective data analysis.

Patients And Setting: All patients over age 30 enrolled in the (staff-model) MCO of Duke University Medical Center between April 1996 and March 1999.

Data Sources: Merged database of MCO administrative, billing, and laboratory files and selected medical records. CASE DEFINITIONS: We identified all patients with abnormal test results suggestive of diabetes (i.e., hemoglobin [Hb] A1c > or = 7.0% or plasma glucose > or = 200 mg/dL) on one or more occasions. Patients were considered to have recognized diabetes if they had an ICD-9 diagnostic code for diabetes in the administrative database or a diagnosis mentioned in their medical record (on the basis of medical record review of a random sample of 30% of patients with abnormal test results and no ICD-9 code). Patients with unrecognized diabetes did not have an ICD-9 code or a medical record diagnosis.

Results: 1426 patients had laboratory tests suggestive of diabetes. Of these patients, 1122 (79%) had an ICD-9 diagnostic code for diabetes in the administrative database. Forty-six of the remaining 304 patients without ICD-9 codes had mention of diabetes on medical record review; thus, we estimate that as many as 258 (18% of patients with laboratory tests suggestive of diabetes) had unrecognized diabetes. When this estimate was restricted to findings that are most suggestive of diabetes (high HbA1c or two high plasma glucose tests), 124 (9%) patients had unrecognized diabetes.

Conclusions: A substantial proportion of patients in an MCO have laboratory values suggestive of diabetes with no evidence that their providers have recognized this condition.