Predicting Abdominal Aortic Aneurysm

Abstract

To the Editor.— — I agree with Beede et al 1 that available data do not support abdominal palpation as a screening tool for abdominal aortic aneurysm (AAA). However, their article is of limited value in assisting clinicians with the decision to order abdominal ultrasonography when AAA is suspected. There is a major flaw in the methods used by the authors. Only patients with clinical suspicion of AAA were included. If one assumes that the gold standard is abdominal ultrasonography and the reference test is clinical suspicion, then no patients without clinical suspicion were included. Thus, it is impossible to construct a 2 × 2 table, calculate truepositive, false-negative, false-positive, and true-negative rates, and impossible to derive positive predictive values. It would have been more meaningful to include an equal number (117) of age- and gender-matched subjects, without a clinical suspicion of AAA, from the Rochester Epidemiology Group. As discussed