An investigation of the specificity value of cTns in diagnosis and exclusion of AMI

Abstract

Objective: The specificity of cTns has not been so satisfactory. The objective of this study is to define a cut point of cTns and CK-MB in diagnosis of AMI. Methods: Measure the serum cTnI, cTnT, and CK-MB of the continuous patients who were admitted in our hospital in three months. 334 cases were collected. They were divided into 6 groups: 30 cases in AMI group, 90 in angina pectoris, 56 in heart failure, 41 in cardiac arrhythmia, 97 in hypertensive, and 20 in uremia. The sensitivity, specificity and the accuracy of cTnI, cTnT and CK-MB were analyzed. Results: The serum cTns and CK-MB concentration in AMI patients were significantly higher than other groups (P<0.05) but the value of them in other groups had overlap with the AMI group. The sensitivity, specificity and accuracy of cTnI for diagnosing AMI were 100%, 81.3% and 82.9% by exceeding the cut off point of 0.14 ng/mL (95th percentile reference value). They were 96.7%, 89.1% and 89.8% by cTnI exceeding twice the cut off point (0.28 ng/mL). The sensitivity, specificity and accuracy of cTnT for diagnosing AMI were 96.7%, 99.6% and 87.4% by exceeding the cut off point; and 93.3%, 99.4% and 99.5% by cTnT exceeding twice the cut off point. The CK-MB were 50%, 85.5% and 82.3% by exceeding the cut off point; and 43.3%, 99.3% and 94.3% by CK-MB exceeding twice the cut off point. Conclusion: cTnI and cTnT both had high sensitivity in diagnosing AMI, but the specificity of cTnT was higher than cTnI. The sensitivity of CK-MB was not high, but the specificity of CK-MB was as high as cTnT. Our result suggests that cTns should have two critical values, one for diagnosis of AMI and another is for excluding non-ischemia damage of myocardium.