Statistical analysis The data were analyzed by using SPSS version 15.0 (SPSS, Chicago, IL, USA). Categorical variables are reported as percentages, and normally distributed data are expressed as mean±SD. Statistical comparisons between two groups performed with Student's t-test for normally distributed data, Mann-Whitney U test for non-normally distributed data, and chi-square test for all numerical and categorical values. The positive predictive value (PPV) for SBI of at least one abnormal criteria and the NPV for SBI of the low-risk criteria, in combination, were calculated by the standard statistical formula. All patients were evaluated according to the Boston, Philadelphia, Rochester and Sisli Etfal protocols, and the results were compared for sensitivity, specificity, NPV, PPV, and accuracy values. For predicting SBI, the serum levels of CRP and WBC count were subjected to receiver operating characteristics (ROC) curve analysis. The results were considered to be significant if analysis yielded p<0.05.