Age-specific and sex-specific differences in diagnostic accuracy of high-resolution ultrasonography for acute appendicitis

Objective: To evaluate the diagnostic capability of high-resolution ultrasonography (HRUS) for clinically suspected acute appendicitis in patients of different sex and age presenting with acute right lower quadrant pain at the Emergency Department of Tri-Service General Hospital, Taipei, Taiwan. Materials and methods: The study included 734 consecutive patients (366 males and 368 females) in whom acute appendicitis was clinically suspected and evaluated using HRUS between January 1997 and November 1999. Patients were classified into two groups by sex, and further classified into four age groups (I = 0-17 yr; II = 18-45 yr; III = 46-60 yr; IV = > 60 yr) for categorical analysis. We retrospectively reviewed and compared the patients' HRUS images with their operative findings and histologic results to evaluate the overall age-specific and sex-specific diagnostic ability of HRUS for acute appendicitis. The chi-square test was used for categorical data analysis. Comparative analysis of our data with previously published data on the correlation between the prevalence of acute appendicitis and sonographic diagnosis of acute appendicitis was performed using linear regression. Results: The overall accuracy, sensitivity, specificity, positive and negative predictive rates were 89%, 87%, 90%, 89% and 88%, respectively. Age-specific analysis revealed a statistically significant difference in diagnostic accuracy between age groups II and III among women (85% vs 96%, respectively; p <0.05). Sex-specific analysis of age group II showed higher sensitivity (90% vs 77%; p <0.05) and positive predictive values (89% vs 77%; p <0.05) in women than in men, respectively. In age group III, the accuracy of HRUS was higher in men than in women (96% vs 84%, respectively; p <0.05). The negative predictive value and overall diagnostic accuracy were negatively correlated to the prevalence of acute appendicitis. Conclusion: The value of HRUS for the diagnosis of acute appendicitis varied among different age and sex groups. The prevalence of acute appendicitis was negatively correlated with the negative predictive value and overall diagnostic accuracy of HRUS for acute appendicitis.