SENSITIVITY AND SPECIFICITY OF THE INITIAL WORKING DIAGNOSIS IN ACUTE MYOCARDIAL-INFARCTION - IMPLICATIONS FOR THROMBOLYSIS

Diagnosing acute myocardial infarction promptly allows all eligible patients to be considered for thrombolysis. Objective evidence from the first electrocardiograph may be inadequate and often the doctor must base his immediate management on limited information; an incorrect initial working diagnosis might deny some patients the benefits of thrombolysis or expose others to inappropriate, expensive and potentially harmful treatment. We were interested to find out how accurate our junior doctors were in their assessment of patients admitted with a suspected MI. All patients entered onto the Nottingham Heart Attack Register admitted with suspected acute MI from 1982 to 1986 and 1989 were identified. The initial working diagnosis on admission was obtained from the patient case record. A final diagnosis was assigned according to strictly defined criteria using 'cardiac' enzyme and electrocardiographic results. Sensitivity and specificity of the initial working diagnosis was calculated. Using the initial working diagnosis as a 'screening' test, we found that, while our doctors successfully identified patients with myocardial ischaemia, they were less good at recognizing acute MI - an admission diagnosis of 'MI' carried a sensitivity of 55% and specificity of 88%. This may explain the low utilization of thrombolysis in the Nottingham hospitals. In the first full year since thrombolysis became available, we estimated that we might have exposed 65 patients to the risks of thrombolysis inappropriately and we might have missed treating 244 patients.