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Clubbing: Kathryn A. Myers, MD, EdM, FRCPC, discusses the clinical examination for clubbing.
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Clubbing: Kathryn A. Myers, MD, EdM, FRCPC, discusses the clinical examination for clubbing.
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Language: EN.
Segment:0 .
>> I'm Joan Stephenson, editor of JAMA's "Medical News and Perspectives" section. Today we'll be hearing from Doctor Kathryn Myers about clubbing, a topic discussed in Chapter 14 of the "Rational Clinical Examination." Welcome to the podcast Dr. Myers, and please introduce yourself to our listeners. >> Thank you very much. I'm Dr. Katherine Myers. I'm a professor of medicine in the department of medicine at Western University, and that's in London, Ontario, Canada. >> Dr. Myers, what is clubbing, and why is detecting it during the clinical examination important?
>> Digital clubbing is characterized by the enlargement of terminal segments of the fingers or the toes that results from a proliferation of the connective tissue between the nail matrix and the distal phalanx. Although clubbing can be a benign hereditary condition, the diagnostic implications in an adult are such that its detection should prompt some consideration of the underlying ideology. And the list of diagnoses that can be associated with clubbing is quite long.
These include neoplastic intrathoracic diseases such as bronchogenic carcinoma, suppurative intrathoracic diseases such as lung abscess, bronchiectasis, and empyema, as well as diffuse pulmonary disease. Over and above pulmonary disease, it's associated with gastrointestinal diseases such as inflammatory bowel disease and cirrhosis, as well as cardiac diseases. And in pediatrics, cyanotic congenital heart disease is a common cause of clubbing. Also infective endocarditis is associated with clubbing.
>> In pediatric patients, what conditions may clubbing signify? >> Unlike the adult population, in the pediatric population clubbing usually represents the progression of a well-established disease such as cystic fibrosis, or uncorrected cyanotic congenital heart disease. >> What is the prevalence of clubbing among adult populations, and on what evidence are these prevalence estimates based? >> The probability of clubbing depends on the underlying illness and the population studied.
In one study of hospitalized in-patients on a general medical ward, one investigator used digital photography to measure nail fold angles as an estimate of clubbing. In this population, the hyponychial angle was used as an abnormal indicator and a criterion for clubbing. And, using that criterion, the prevalence of clubbing was 8.9%. Within that medical population, the disease conditions associated with clubbing were broken down.
And the most common association was pneumonia with a prevalence of 23%, followed by HIV disease and cirrhosis at 16% each. A number of other conditions were noted to be associated with clubbing, including hepatitis, bronchogenic carcinoma, and pulmonary hypertension. >> Dr. Myers, is there a reference standard available to verify a diagnosis of clubbing? >> Several quantitative measures have been used to detect clubbing in a number of research studies.
These include shadowgrams to measure nail fold angles, and special devices called [inaudible] to also measure nail fold angles. Plaster finger casts have been used to look at the width and depth of fingers. None of these is practical at the bedside, and so the pragmatic gold standard is the clinical examination where estimation of nail fold angles and depth ratios can be used to look at the presence or absence of clubbing.
>> Can you please describe the differences between a finger that appears normal and one that appears clubbed? >> Inspection of the fingers for clubbing can reveal a number of abnormalities in both the nail fold angles and in the shape, depth, and width of the terminal part of the finger. In addition to the obvious changes in shape that you see with advanced and established clubbing, a close inspection of the cuticle of the nail may reveal shiny and smooth appearance in that area.
And this is described as a lilac hue of the nail fold. And this is caused by the increased vascularity in the connective tissue at that nail fold. There are a number of other ways to inspect the fingers including looking at nail fold angles and the phalangeal depth ratio. First, the nail fold angles are two angles. One called the profile angle which was popularized many years ago by Lovibond. He noticed that in normal fingers, the nail projects from the nail bed at an angle of about 160 degrees.
In patients with clubbing, this angle approaches a straight line or 180 degrees. The hyponychial angle has also been proposed as a more reliable sign than the profile angle in the assessment of clubbing, but it's harder to estimate at the bedside. In the normal finger, the distal phalangeal depth should be smaller than the interphalangeal depth. In clubbing, as connective tissue starts to deposit and expand the pulp in the terminal phalanx, this ratio becomes reversed.
Although the phalangeal depth ratio was originally described and measured using plaster casts and shadowgrams, it can be measured at the bedside with calipers, and the calipers should touch but not compress the tissue at the distal phalanx and the interphalangeal joint. This ratio should not be above one. And if it is above a one, it suggests clubbing is present. Another very popular sign performed at the bedside is called Schamroth sign. This was reported by Schamroth in 1976.
This clinical sign incorporates two of the clinical features of clubbing. Normally fingers create a diamond-shaped window when the dorsal surfaces of the terminal phalanx of similar fingers are opposed. In the clubbed finger, the diamond becomes obliterated because of the loss of the profile angle, and they increase in the soft tissue at the cuticle. >> Dr. Myers, how accurate is the clinical examination for clubbing? >> Because of the lack of an objective diagnostic criterion standard, accuracy of the physical examination for clubbing is difficult to determine.
Determination of the accuracy to detect clubbing has also been confounded in a number of studies by incorporation bias. This results when the clinical examination itself performs part, or all, of the diagnostic criterion standard. An alternative approach is to consider the accuracy of the presence of clubbing as a marker of underlying disease. Since so many patients with clubbing have pulmonary disease, one relevant clinical question is whether clubbing separates those with COPD from those who have clubbing associated with pulmonary malignancy.
Baughman looked at this question by measuring the phalangeal depth ratio in patients with COPD, pulmonary malignancy, and controls. He used calipers to measure the PDR or phalangeal depth ratio. What he found was that none of the control subjects had a PDR in excess of one. In those patients who had a PDR above one, 40 had lung cancer and five had COPD alone, for a likelihood ratio positive of 3.9. The likelihood ratio negative was 0.7 and as these data confirm, although a normal PDR does not rule out lung cancer, an abnormal ratio implies an increased probability of disease.
Kitis looked at the association of clubbing with the activity of inflammatory bowel disease in 327 patients, and he used shadowgraph-measured hyponychial angles as his gold standard. What he found was that the likelihood ratios for clubbing as a marker of active Crohn's disease was 2.8, and for ulcerative colitis, 3.7. These both indicate that more active inflammatory bowel disease is associated with a modest likelihood ratio positive with clubbing.
>> Is there anything else you would like to tell our listeners about the clinical examination for clubbing? >> I would start by quoting Samuel West who said that clubbing is one of those phenomena with which we are all so familiar, that we appear to know more about it than we really do. Although there's no published evidence that tells us the diagnostic yield or the optimal strategy for investigating a patient with clubbing, a thorough history and physical examination should be performed in any patient where the phalangeal depth ratio is above one, or the profile angle exceeds a straight line or 180 degrees.
Since pulmonary disease is one of the most common underlying causes of clubbing, patients should have a chest x-ray at a minimum. But further investigation should be guided by the history and physical examination since the differential diagnosis of clubbing is so broad. >> Thanks very much, Dr. Myers, for this helpful view of clubbing and its significance. Additional information about this topic is available in Chapter 14 of the "Rational Clinical Examination." This has been Joan Stephenson of JAMA, talking with Dr. Kathryn Myers about clubbing for JAMAevidence.
