Positive Predictive Value of the Thumb-Palm Test for General Population Screening of Ascending Aortic Aneurysm

An important consideration in evaluating the clinical utility of a screening test is the positive predictive value, or the post-test probability that a patient with a positive finding actually has the related disease condition.2 Although the authors note that their estimated positive predictive value of 70% is skewed upward because of a disease-enriched population, multiple news sources have since recommended broad use of the thumb-palm test. A recent systematic review and meta-analysis estimated the prevalence of thoracic aortic aneurysm as 0.07% and 0.76% in non–autopsy- and autopsy-based population studies, respectively.3 We used non–autopsy-based studies to estimate instantaneous prevalence and autopsy-based studies to estimate lifetime cumulative risk (Table 1). Because the study by Blumel et al1 specifically addresses ascending aneurysms and only 60% of thoracic aortic aneurysms are found in the ascending region,4 we adjusted prevalence estimates accordingly to 0.042% for baseline prevalence and 0.46% for lifetime cumulative prevalence, which represent pretest probabilities. Population Pretest probability Post-test probability Thoracic aortic aneurysm Ascending aortic aneurysm Ascending aortic aneurysm General population (nonautopsy studies)3 0.07% 0.042% 0.096% General population (autopsy studies)3 0.76% 0.46% 1.0% Intracranial aneurysm5 7.5% 4.5% 10% Abdominal aortic aneurysm6 19% 12% 26% Table 1 Pretest and post-test probabilities of an ascending aortic aneurysm after a positive thumb-palm test in various populations