A Case of Clubbing

I saw a patient in the rapid referral GIM clinic this patient was referred for digital clubbing. He was a younger patient who had never been seriously ill. He mentioned in his past he had been worked up for a "leaky valve". Reviewing the chart showed he had mild aortic insufficiency. During his current workup he had seen a cardiologist who did not believe that this issue would be able to explain his symptoms. The patient felt well and had no symptoms he could mention, but told me that his nails had visibly changed shape in the past few months. His main concern was curiosity about what was going on and worry about possible serious issues. I began my physical exam, and realized that while I had been exposed to clubbing as a concept, my knowledge base was not deep in this area. I was able to appreciate an abnormality in the morphology of the patients nails, but didn't have a firm grasp of definitive physical exam maneuvers to rule in or rule out true clubbing. I checked for the Schamroth Sign (which was negative), but not much beyond that. I brought this up to my preceptor who I was glad helped point me to the JAMA Rational Clinical Exam article on clubbing. I was surprised to learn that there is no gold standard test for clubbing, and that the diagnosis is made mostly on clinical exam with techniques that are not very well established. Additionally, studies have shown that interobserver agreement is only fair to moderate. One of the most helpful measures is the phalangeal depth ratio between the distal phanalgeal depth (DPD) and the interphalangeal depth (IPD) which in disease free populations rarely exceeds 1.0. This is best measured with calipers - if there are no calipers reversal of the usual IPD>DPD to IPD<DPD can be useful. Another useful measure is the nail-fold angle, which rarely exceeds 180 degrees in disease free subjects. I learned that clubbing can be a manifestation of significant disease (including cardiac, pulmonary, and various malignancies) so despite the difficulties establishing definitive physical exam criteria it is an important finding to look for. I appreciated this opportunity to develop my physical exam skills and engage in point-of-care learning during this encounter in the clinic.

- MH