It is our institution’s practice to remove all appendixes even if there were no macroscopic features of acute appendicitis intraoperatively. GDC-0068 cost This is guided by existing data, which revealed that up to 33% of macroscopically normal appendixes have features of inflammation on histology.12 The range of AS for which patients were least likely to benefit from CT evaluation was determined by identifying AS ranges that had positive likelihood ratios not significantly different from those of CT scans. Likelihood ratios were

selected as the parameter for comparison because they were independent of disease prevalence and depended only on the intrinsic ability of the diagnostic test to distinguish between diseased and nondiseased individuals. The pairwise comparisons of predictive values and likelihood ratios are based on the methods described by Moskowitz and Pepe (2006)13 and Nofuentes and Castillon (2007),14 respectively. The above statistics were sub-analyzed by sex because the performance of the AS has been shown to vary according to sex.15 Statistical analyses were performed using Statistical Package for the Social Sciences (SPSS) Version 17. Performance measures, including sensitivity, specificity, positive and negative AP24534 purchase predictive values, and diagnostic likelihood

ratios were calculated and compared using the BDT comparator program.16 A p value of less than 0.05 was considered to indicate statistical significance. The study was carried out under the approval of the Centralized Institutional Review Board of the Singapore Health Services. There were 450 patients admitted for suspected appendicitis from August 2013 to March 2014. One hundred patients were not evaluated with CT scans and were excluded from the study. Altogether, 350 patients underwent CT evaluation. There were no cases of missed diagnosis in these patients, who were all evaluated with CT scans. There were 134 males (38.3%) and 216 females (61.7%). The overall

Adenosine median age of the patients was 33 years (range 15 to 82 years): 32 years for males and 33 years for females. Among the 350 patients who presented with suspected appendicitis and were evaluated with CT scans, the overall prevalence of appendicitis was 44.3% in the total study population; 37.5% in females and 55.2% in males (Fig. 1). Nineteen (5.4%) of the CT scans were deemed equivocal, 11 in females and 8 in males. Surgery was performed for 168 patients (48%), of whom 40, 126, and 2 underwent open appendectomy, laparoscopic appendectomy, and laparotomy, respectively. The overall negative appendectomy rate was 7.7%. The number of patients within each AS cut off category is illustrated in Table 2. The sensitivity, specificity, positive and negative predictive values, and positive likelihood ratio of the various AS cut-off values compared with CT scan are illustrated in Table 3. Sub-analysis of the positive likelihood ratios of the various AS values stratified by sex and compared with CT scan are illustrated in Table 4.