Diagnostic value of high sensitivity C-reactive protein in differentiating unstable angina from myocardial infarction

BACKGROUND: Differentiating between unstable angina and myocardial infarction (MI) is clinically important as they require different treatments. High sensitivity C-reactive protein (hs-CRP) has recently been recognized as prognostic factor in acute coronary syndrome. Since this biomarker may indicate the prognosis of heart disease, identifying its diagnostic value will be clinically important. This study investigated the diagnostic value of the level of hs-CRP in differentiating MI from unstable angina. METHODS: Blood samples were obtained from all patients with suspected MI or unstable angina at the time of referral. The patients were put in one of the two groups based on final diagnosis. The exclusion criteria were infectious diseases, immune system diseases, history of a recent surgery or trauma, kidney failure, liver failure, cancers, and use of anti-inflammatory drugs. Data was entered in SPSS and analyzed by independent t-test, Mann-Whitney U and chi-square or Fisher's exact test. ROC curve was used to determine hs-CRP cut-off point. The sensitivity and specificity were calculated at the cut-off point. RESULTS: Overall, 60 patients (30 patients with MI and 30 patients with unstable angina) were studied. Hs-CRP level was 3.68 ± 0.86 mg/l in patients with MI and 2.35 ± 1.30 mg/l in patients with unstable angina (P < 0.001). The best cut-off point for differentiating unstable angina from MI was hs-CRP levels equal to or greater than 3.27 mg/l. At this cutoff point, the sensitivity and specificity were both 77%. CONCLUSION: Patients with MI had higher levels of hs-CRP than subjects with unstable angina. Hs-CRP levels equal to or higher than 3.27 mg/l are more likely to be associated with MI. It is recommended to test this biomarker in all patients with acute coronary syndrome.