A study of capillary morphology in the digits of patients with acquired clubbing.

We sought to determine the capillary morphology in patients with clubbing to compare it with that in subjects without clubbing. Subjects were placed in the clubbed or nonclubbed groups on the basis of caliper measurements of their index fingers. In each subject, photomicrographs of eight fingers were done focusing on the dorsal skin just proximal to the base of the nail. Each photomicrograph was randomly graded with respect to the presence and extent of plexus formation, the presence of arborized loops, and the presence of splayed loops. Comparison of the plexus score, presence of arborized loops, and presence of splayed loops were significantly different between the clubbed and nonclubbed groups (p less than 0.001 in all three analyses). Only a plexus score of 2 or greater demonstrated a useful degree of sensitivity and specificity (89 and 90%, respectively). We concluded that a significant difference in the morphologic features of the capillaries existed between nonclubbed subjects and those with acquired clubbing.