Determining the predictive value of Read/OXMIS codes to identify incident acute myocardial infarction in the General...

To determine (1) the positive predictive value (PPV) of multiple Read/OXMIS codes to identify incident acute myocardial infarction (AMI) cases in General Practice Research Database (GPRD); (2) the ability to capture the correct timing of the clinical event.

A random sample of 238 records (from 155 general practitioner (GP) practices) with AMI codes, between 1 January 1997 and 31 December 2004, was selected from GPRD. Questionnaires were sent to the GPs to verify the diagnosis and timing of code-identified incident AMI events and collect supporting information. We calculated the PPV of the AMI codes as the proportion of code-identified AMIs that the GPs confirmed as AMI cases. Two physicians from Food and Drug administration (FDA), blinded to the GP response, reviewed the supporting hospital records returned by GPs for 98 AMI cases.

A total of 217 questionnaires were completed (91% response rate). The PPV of the AMI codes was 93% (201/217). Thirty one (15%) cases had a different event date than the one recorded in the electronic medical records (EMR); 28 (90%) of the dates were within 15 days. One GP indicated that a patient had a previous AMI, 110 days before the codes that captured the AMI diagnosis. A total of 159 (79%) AMI cases were hospitalized; hospital records were provided for 98 patients. Physician review of the hospital records found that 96% of these records had enough information for classification, but not independent diagnosis, of AMI.

Information in GPRD is sufficient to identify incident AMI cases and determine the event date with reasonable accuracy.