A comparative evaluation of C-reactive protein as a short-term prognostic marker in severe unstable angina--a preliminary study.

ABSTRACT

OBJECTIVE: The present study was done to evaluate the short-term prognostic significance of C-reactive protein (CRP) in unstable angina (UA) and to compare it with other known prognostic markers of UA, as there is a paucity of data from our country. METHODOLOGY: This prospective study comprised of 44 UA patients (Braunwald Class II A, B) with age < 65 years, along with 40 age and sex matched healthy controls. Patients with h/o myocardial infarction (MI) in the preceding 1-month and evidence of infection, inflammation or neoplasm were excluded from the study. Complete clinical evaluation was done and presence of any prognostic variables of UA was noted (including Brauriwald high-risk variables). Apart from biochemical investigations and ECG, CRP was measured at the time of admission in the study group and controls using Microwell ELISA assay. Standard treatment protocol was followed for all patients and they were closely monitored during hospital stay and subsequently for 4 weeks for occurrence of any adverse cardiac events. RESULTS: There was a statistically significant difference in the mean level of CRP between study group (6.12 +/- 6.134 mg/L) and controls (1.52 +/- 0.751 mg/L); p = 0.000. Among the 44 patients, 19 (43%) experienced any one or more outcome measures. Of the three variables (i.e. ongoing chest pain, ST depression > or = 1 mm and CRP > or = 4 mg/L) which showed statistical significance on univariate analysis with respect to adverse outcome measures (p = 0.001, 0.027 and 0.000 respectively), only CRP > or = 4 mg/L and ST depression > or = 1 mm showed independent prognostic significance on multiple logistic regression analysis (p = 0.000 and 0.002 respectively). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and relative risk (RR) for CRP > or = 4 mg/L were 78.9%, 96%, 93.75%, 85.74% and 6.56 (95% CI; 2.62 - 16.4) and that for ST depression > or = 1 mm were 89.47%, 64%, 65.38%, 88.89% and 5.88% (95% CI 1.54 - 22.38), respectively. Trop T could be done in eight patients only. CONCLUSION: CRP > or = 4 mg/L by ELISA is an independent predictor of adverse cardiac outcome in severe UA in the short-term follow up and, hence, is useful for risk stratification of these patients. CRP has a higher specificity, PPV and overall RR for prediction of an outcome than ST segment depression, although it is less sensitive.