Quantitation of digital clubbing children. Measurements of casts of the index finger.

Abstract

Casts of the left index finger were made in 267 normal infants, children, and adults, as well as in 146 infants and children with various diseases (45 with cystic fibrosis, 40 with heart disease, 45 with asthma, and 16 with other types of pulmonary disease). Measurements were made of each cast to obtain a simple but specific quantifiable parameter of clubbing. Measurements included fingernail-skinfold angle, longitudinal fingernail radius, lateral fingernail radius, distal phalangeal­ interphalangeal depth ratio, and distal phalangeal-interphalangeal width ratio. The best measure of dubbing of those studied was distal phalangeal-interphalangeal depth ratio, which in normal children is independent of age, sex, height, and weight, and best discriminates between normal subjects and patients with diseases commonly associated with digital dubbing, such as cystic fibrosis and cyanotic congenital heart disease. Mean (±SD) normal distal phalangeal-interphalangeal depth ratio was 0.895 ± 0.041. A value for distal phalangeal-interphalangeal depth ratio exceeding 1.0 (corresponding to 2.5 SD greater than the normal mean) was observed in only one of 267 normal subjects, but in 62 of 68 casts from patients with cystic fibrosis. Errors in accuracy and precision are introduced by measuring distal phalangeal-interphalangeal depth ratio by simpler methods on living fingers. Finger casting is an excellent means of studying serial changes in the degree of clubbing in the same patient.