Objective: Clubbing can be a paraneoplastic manifestation of bronchogenic carcinoma. We assessed a new digital index of clubbing and used it to determine the prevalence of clubbing for different cell types of lung cancer.
Methods: Clubbing was assessed by measurement of the thickness of both the base of the nailbed (distal phalangeal depth--DPD) and the distal interphalangeal depth (IPD) of the index finger in a control group compared to patient groups with either chronic obstructive lung disease, or lung cancer.
Results: Of the 55 normal subjects, no patient had a DPD/IPD ratio of more than 1.05 on either hand, while 11% of the patients with COPD had a ratio of more than one. For the cancer patients, 33% had a ratio greater than one, with 30 of 109 (37%) having a ratio > 1.05 (chi(2) = 17.6, p < 0.0001). There was no difference in the prevalence of clubbing between the 33 squamous cell patients, the 43 adenocarcinoma patients, and the 33 small cell lung carcinoma patients included.
Conclusions: Measurement of the interphalangeal and distal phalangeal distance demonstrated that one-third of patients with lung cancer had evidence of clubbing. The type of bronchogenic carcinoma did not appear to affect the proportion of patients with clubbing.