The association between digital clubbing and a host of diseases has
been recognized since the time of Hippocrates. Although the features of advanced
clubbing are familiar to most clinicians, the presence of early clubbing is
often a source of debate.
To perform a systematic review of the literature for information on
the precision and accuracy of clinical examination for clubbing.
The MEDLINE database from January 1966 to April 1999 was searched for
English-language articles related to clubbing. Bibliographies of all retrieved
articles and of standard textbooks of physical diagnosis were also searched.
Studies selected for data extraction were those in which quantitative
or qualitative assessment for clubbing was described in a series of patients.
Sixteen studies met these criteria and were included in the final analysis.
Data were extracted by both authors, who independently reviewed and
appraised the quality of each article. Data extracted included quantitative
indices for distinguishing clubbed from normal digits, precision of clinical
examination for clubbing, and accuracy of clubbing as a marker of selected
The profile angle, hyponychial angle, and phalangeal depth ratio can
be used as quantitative indices to assist in identifying clubbing. In individuals
without clubbing, values for these indices do not exceed 176°, 192°,
and 1.0, respectively. When clinicians make a global assessment of clubbing
at the bedside, interobserver agreement is variable, with κ values ranging
between 0.39 and 0.90. Because of the lack of an objective diagnostic criterion
standard, accuracy of physical examination for clubbing is difficult to determine.
The accuracy of clubbing as a marker of specific underlying disease has been
determined for lung cancer (likelihood ratio, 3.9 with phalangeal depth ratio
in excess of 1.0) and for inflammatory bowel disease (likelihood ratio, 2.8
and 3.7 for active Crohn disease and ulcerative colitis, respectively, if
clubbing is present).
We recommend use of the profile angle and phalangeal depth ratio as
quantitative indices in identifying clubbing. Clinical judgment must be exercised
in determining the extent of further evaluation for underlying disease when
these values exceed 180° and 1.0, respectively.