Q J Med 2001; 94: 397-398
© 2001 Association of Physicians
Correspondence |
Evidence-based diagnosis of severe aortic stenosis
Assistant Professor of Medicine Mayo Clinic, Rochester, USA
Sir,
The recent article by Das et al.1 describes the difficulties encountered in clinical practice in the diagnosis of aortic stenosis. Recent emphasis on the use of likelihood ratios to emphasize symptoms, signs and diagnostic tests has greatly enhanced appreciation of clinical data.2 The use of likelihood ratios in medical decision-making has been greatly emphasized in an article by Dujardin et al.3 The many challenges of clinical examination include the presence of disease despite negative signs (poor sensitivity), interobserver variability, and variable observer experience, all of which make diagnosis of severe aortic stenosis so challenging.
A recent study4 of the LR+ (positive likelihood ratio, when symptoms are present) and LR- (negative likelihood ratio, when findings are absent) for the physical signs of aortic stenosis found that the presence of the following signs greatly increased the likelihood of aortic stenosis; slow rise of carotid pulse (LR+ 130, LR- 0.62, decreased intensity of second heart sound (LR+ 50, LR- 0.45), late peaking of peak systolic murmur (LR+ 101, LR- 0.31), apical-carotid delay (LR+ infinity, LR- 0.05). Similarly, the absence of systolic murmur (LR- 0.0) or radiation of murmur to the right carotid artery (LR- 0.10), greatly reduced the chance of AS. Combination of clinical variables such as decreased carotid volume, delayed carotid upstroke, decreased or absent S2, murmur loudest at the second right intercostal space and valve calcification could result in a LR+ varying from 0.10 to infinity, depending upon the presence of one or all variables.4 Additionally, a clinical assessment of abnormal murmur by a cardiologist significantly increases the likelihood of cardiac abnormality.
A useful clinical prediction rule is that LR+ >10 confirms the diagnosis, while LR- <0.10 rules out a diagnosis.5 Given the relatively high LR- of clinical signs of aortic stenosis, in patients suspected to have a high prevalence of aortic stenosis, it is necessary to go to echocardiography rather than rely on any one or more clinical signs.
References
1. Das P, Pocock C, Chambers J. The patient with a systolic murmur: severe aortic stenosis may be missed during cardiovascular examination. Q J Med2000; 93:685–8.
2. Sackett DL. A primer on the precision and accuracy of the clinical examination. JAMA1992; 267:2638–44.
3. Dujardin B, Van den Ende J, Gompel AV, Unger J, Stuyft PV. Likelihood ratios: A real improvement for clinical decision making? Eur J Epidemiol1994; 10:29–36.
4. Etchells E, Bell C, Robb K. Does the patient have abnormal systolic murmur? JAMA1997; 277:564–71.
5. Jaeschke R, Gordon H, Guyatt G, Sackett DL. Users' guides to the medical literature. III. How to use an article about a diagnostic test. B. what are the results. JAMA1994; 271:703–7.
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