Diagnostic codes for sudden cardiac death and ventricular arrhythmia functioned poorly to identify outpatient events in EPIC's General Practice Research Database

Purpose To examine the validity of OXMIS/Read diagnoses of hospitalization for sudden cardiac death and ventricular arrhythmia (SD/VA) for use in studies of arrhythmogenic effects of outpatient medications in the General Practice Research Database (GPRD). Methods We identified putative occurrences of hospitalization for SD/VA inpatients receiving outpatient prescriptions for cisapride, domperidone, or metoclopramide. We then administered a questionnaire to general practitioners (GPs) caring for these patients, requested hospital discharge consult letters, and examined the positive predictive value (PPV) of diagnostic codes in identifying outpatient events precipitating hospitalization. Results We identified 84 putative events, 38 (45%) of which occurred in patients cared for by GPs participating in the follow-up scheme. Thirty of 38 questionnaires (79%) were completed. The PPV for the occurrence of any SD/VA was 93% (95% CI, 78-99%). However, the PPV for SD/VA occurrence in an outpatient setting precipitating a hospitalization was only 23% (95% CI, 10-42%). The majority of inpatient diagnostic codes reflected events occurring after hospital admission, not precipitating it. Conclusions While computerized codes for SD/VA agreed well with physician diagnosis, they operated poorly to identify events occurring in an outpatient setting. Studies of SD/VA in the GPRD should verify events on a case-by-case basis. Copyright (C) 2008 John Wiley & Sons, Ltd.