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Measuring finger clubbing.

Measuring finger clubbing.
Measuring finger clubbing.

The ratio of the anteroposterior diameter of the finger at the nail bed (a–b) to that at the distal interphalangeal joint (c–d) is a simple measurement of finger clubbing. It can be obtained readily and reproducibly with calipers. If the ratio is > 1, clubbing is present. Finger clubbing is also characterized by loss of the normal angle at the nail bed.