Effect of age on the performance of single detector helical computed tomography in suspected pulmonary embolism

The prevalence of pulmonary embolism increases with age, but reduces the diagnostic yield of ventilation-perfusion lung scan age. Helical computed tomography (hCT) is widely used to diagnose pulmonary embolism, and should be less susceptible to the influence of age. We studied the influence of age on the performance of hCT to verify that hypothesis. We analyzed a database of 299 consecutive outpatients suspected of pulmonary embolism, in whom pulmonary embolism was diagnosed according to accepted criteria, and who were all submitted to a helical CT We divided the patient population into tertiles, corresponding to the following age categories: less than 59 years (group 1), 60 to 75 years (group 2), and over 75 years (group 3). Sensitivity and specificity of hCT were calculated in each age category. Overall sensitivity was 70% (95% CI: 62 to 78) and specificity was 91% (95% CI: 86 to 95). Sensitivity was 81% (95% CI: 64 to 93) in group 1, 63% (95% CI: 46 to 78) in group 2, and 67% (95% CI: 52 to 80) in group 3. The corresponding values for specificity were 92% (95% CI: 82 to 97) in group 1, 86% (95% CI: 75 to 94) in group 2 and 96% (95% CI: 87 to 100) in group 3. Positive predictive values ranged from 75% to 94% and negative predictive values from 77% to 94%. Our data suggest that age does not have a marked influence on the diagnostic performances of hCT in clinically suspected pulmonary embolism.