An assessment of the validity of ICD code 410 to identify hospital admissions for myocardial infarction: The Corpus Christi Heart Project

Background. The identification of myocardial infarction (MI) is typically based on finding events designated by a nosologist with the appropriate International Classification of Diseases (ICD) code, currently code 410. These codes are applied based on review of medical records or death certificates. However, other factors, including reimbursement considerations, may influence the coding process, especially for hospitalizations. Thus, the validity of using ICD code 410 to identify MI must be assessed. Methods. The Corpus Christi Heart Project (CCHP) is a population-based surveillance programme for hospitalized MI. Patients were identified using concurrent ascertainment in coronary care units and retrospective review of medical records. Events were validated as definite or possible MI using data regarding chest pain, electrocardiographic changes and cardiac enzymes. The validity of using ICD code 410 to identify cases of MI was assessed by calculating the sensitivity, specificity, predictive values and efficiency of ICD code 410 versus the CCHP 'gold standard'. Results. Use of ICD code 410 identified 80.9% (401/496) of definite MI, but only 19.0% (243/1280) of possible MI. Only 12.3% (90/734) of discharges with an ICD 410 code received a 'no MI' designation based on the 'gold standard'. The efficiency of ICD code 410 for identifying MI was 92.0% for definite MI and 77.1% for definite and possible MI. Conclusions. The use of ICD code 410 to identify hospitalized cases of MI results in a modestly biased overestimate of the number of definite MI hospitalizations; however, this approach warrants consideration due to the expense of validation procedures.