Accuracy of the "Thumb-Palm Test" for Detection of Ascending Aortic Aneurysm

We have noticed, in caring for thousands of patients with ascending aortic aneurysm (AscAA), that the "thumb palm test" is often positive (with the thumb crossing beyond the edge of the palm). It is not known how accurate this test may be. We conducted the thumb-palm test in 305 patients undergoing cardiac surgery with intra-operative transesophageal echocardiography (TEE) for a variety of disorders: ascending aneurysm in 59 (19.4%) and non-AscAA disease in 246 (80.6%) (including CABG, valve repair, and descending aortic aneurysm). The TEE provided a precise ascending aortic diameter. The thumb palm test gave us a discrete, binary positive or negative result. We calculated the accuracy (sensitivity and specificity) of the thumb palm test in determining presence or absence of AscAA (defined as ascending aortic diameter > 3.8cm). Maximal ascending aortic diameters ranged from 2.0 to 6.6 cm (mean 3.48). 93 patients (30.6%) were classified as having an AscAA and 212 (69.4%) as not having an AscAA. 10 patients (3.3%) had a positive thumb-palm test and 295 patients (96.7%) did not. Sensitivity of the test (proportion of diseased patients correctly classified) was low (7.5%), but specificity (proportion of non-diseased patients correctly classified) was very high (98.5%). This study supports the utility of the thumb-palm test in evaluation for ascending thoracic aortic aneurysm. That is to say, a positive test implies a substantial likelihood of harboring an ascending aortic aneurysm. A negative test does not exclude an aneurysm. In other words, the majority of aneurysm patients do not manifest a positive thumb-palm sign, but patients who do have a positive sign have a very high likelihood of harboring an ascending aneurysm. We suggest that the thumb-palm test be part of the standard physical examination, especially in patients with suspicion of ascending aortic aneurysm (e.g. those with a positive family history).