[Validity of clinical tests to confirm or exclude the diagnosis of acute myocardial infarction]

Abstract

Background: To know the clinical usefulness of the diagnostic tests habitually used to diagnose an acute myocardial infarction (MI), in a group of patients in which this diagnosis is clinically highly suspected.

Patients and methods: A cross sectional study was designed. The sample (n = 114) was randomized and selected by term and specific of days from the patients attending the Emergency Service at Elda General Hospital (Alicante, Spain) in a year period. The method we used was is a validity study, making 2 x 2 tables. The clinical outcome was the gold standard and was cross matched with some of the clinical criteria habitually used to diagnose acute myocardial infarction: thoracic pain character, irradiation, ECG findings and CK-MB levels.

Results: Clinical suspicion of MI was confirmed in only 27.8% (IC--95%: 19.3-36.3). The best validity indexes of clinical usefulness to confirm the MI diagnosis were obtained from ECG findings (CP+ = infinity) and CK-MB (CP+ = 24.2 at the end of the observational period and CP = 17.9 at the beginning). The best negative clinical validity indexes were CK values obtained at the end of the observational period (CP- = 0.07) and the ECT findings obtained at the end of the observational period (CP- = 0.10).

Conclusion: Clinical carefulness is essential to avoid a diagnostic mistakes in MI patients, since the symptoms we used as a diagnostic guide do not offer good validity indexes. Changes in ECG or CK-MB levels could confirm the MI diagnosis but normal findings in both tests did not discard this diagnosis. We should keep the possibility of a mistake till the end of the observational period.