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Troponin i blood level value and its utility in differentiating myocardial infarction from pulmonary embolism

Authors:Eman Badawood, Lama Saleh, Hadeel AlQahtani, Dr.Amr Albanna
Int J Biol Med Res. 2017; 8(1): 5870-5873  |  PDF File

Abstract

Background: Troponin I (Trop-I) is considered the most sensitive cardiac biomarker for diagnosis of acute MI. However, it lacks specificity since it can be elevated with other conditions such as pulmonary embolism and non-coronary cardiac disorders.Our primary objective is to determine the cut-off blood level values of Trop-I that has the best sensitivity and specificity for differentiating MI from PE. Methods: We performed aretrospective chart review of122 patients admitted to King Abdulaziz Medical City-Western Region with diagnosis of MI or PE between October 2012 and March 2014.We included patients with measured Trop-I blood level and excluded patients with end stage renal disease or chronic elevation of Trop-I. The primary outcome was to estimate the sensitivity and specificity of Trop-I at different level in comparison to the clinical diagnosis. Diagnosis of MI was based on the third universal consensus definition of MI, and the diagnosis of PE was based on CT pulmonary angiogram or ventilation perfusion scan. The secondary objectives were to determine any association between Trop-I elevation with left ventricular (LV) dysfunction among MI patients and with right ventricular (RV) dysfunction among PE patients. Data was analyzed using chi-square, t test, or regression analysis as appropriate. Statistical significance was determined using two-tailed p-value of 0.05. Results:Among 122 patients included, 64 were diagnosed to have MI and 58 were diagnosed to have PE. 58% were males with mean age of 61 years. Figure 1 shows the ROC curve, which describes the diagnostic performance of Trop-I for differentiating MI from PE. At Trop-I blood level of 0.05, the sensitivity is 98.4% (95% CI: 91.6 – 100%) and specificity is 84.5% (95% CI: 72.6 – 92.7%). At the level of 0.1, the sensitivity is reduced to 76.6% (95% CI: 64.3 – 86.2%) but with almost perfect specificity of 98.3% (95% CI: 90.8 – 100%). No association was identified between post-MI Trop-I level and echocardiographic finding of ventricular wall motion abnormality (OR, 1.02; 95% CI: 0.98 – 1.05) or LV dysfunction (OR, 1.02; 95% CI: 0.99 – 1.04). There was a strong association between post-PE elevation of Trop-I and RV dysfunction (p-value = 0.002). Conclusion: The blood level of Trop-I may have clinicalimplication in differentiating MI from PE at the initial presentation. Trop-I level is not associated with LV dysfunction among MI patients, but has strong association with RV dysfunction among PE patients.