Q J Med 2003; 96: 687-688
© 2003 Association of Physicians
Correspondence |
A cost-effective objective approach to aid diagnosis of deep-vein thrombosis (DVT) and pulmonary embolism (PE)
Sir,I read with interest the article by Iles et al.,1 which is the first study to show the effect of clinical experience on the inter-rater variability of the Geneva and Wells scores (and empirical judgement) in the diagnosis of pulmonary embolism (PE). The Geneva and Wells scores are clinical pre-test probability (PTP) scores derived from large trials that reliably predict the diagnosis of PE. I agree with the authors’ view that these scoring systems must be accurate and must be reliable. Their study was to check the inter-rater variability of the three methods, as one measure of reliability is inter-rater variability.
It is often assumed that less experienced doctors are not as capable of determining the PTP of PE. Iles et al. concluded that this was due to clinicians being more conservative in assessing risks.1 This contradicts the Geneva study group’s original evaluation, where they found the accuracy of the empirical assessment was similar to that of the PTP score.2 Moreover, the Geneva score tended to identify the patients with high probability more accurately than empirical evaluation.
The Wells score4 relies heavily on the clinician's judgement as to whether another diagnosis is as likely, or more likely, than PE. Moreover, its complexity renders it difficult to apply in practice. In contrast, the Geneva score is simple and completely standardized.2 The Wells score, however, may be preferred when a suspected PE occurs in a hospital in-patient rather than at the emergency department.2
It was heartening to see that the inter-rater variability of both the Geneva and the Wells scores were not affected by the experience of the assessing clinician in the Iles study, as the majority of the patients in an emergency setting will be managed initially by the most junior doctors. This compares well with the Italian study where assessment was carried out by a limited number of highly specialized pulmonary physicians.3
The Geneva score is based on clinical, arterial blood gas analysis, and chest X-ray findings.2 This allows a standardized and accurate diagnosis of an important subset of patients with low likelihood of PE. Wells et al. have shown that a low PTP and a negative D-dimer test has a NPV of 98% when excluding PE.4 It is not acceptable to miss a DVT in any patient. The NPV of any test or combination of tests must approach 100%.
Flanagan et al. recently reported the utility of computed strain gauge plethysmography as a satisfactory first-line investigation for the diagnosis of DVT.5 Digital photoplethysmography has also been shown to be a very safe tool in this regard.6,7 Both studies showed a NPV of 97%. Applying Bayes’ rule, it is possible that by using the Geneva score, D-dimer and possibly plethysmography for diagnosing DVT and or PE, the negative predictive value may approach 100%. As plethysmography is cheap, this may become the most cost-effective approach to diagnosing DVT.8
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Royal Gwent Hospital Newport email: ranjitsinharay{at}hotmail.com
References
1. Iles S, Hodges AM, Darley JR, Frampton C, Epton M, Beckert LEL, Town GI. Clinical experience and pre-test probability scores in the diagnosis of pulmonary embolism. Q J Med 2003; 96:211–15.
2. Wicki J, Perneger TV, Junod AF, Bounameaux H, Perrier A. Assessing clinical probability of pulmonary embolism in the emergency ward: a simple score. Arch Intern Med 2001; 161:92–7.
3. Miniati M, Prediletto R, Formichi B, et al. Accuracy of clinical assessment in the diagnosis of pulmonary embolism. Am J Respir Crit Care Med 1999; 159:864–71.
4. Wells PS, Anderson DR, Rodger M, Ginsberg JS, Kearon C, Geut M, Turpie AGG, Bormanis J, Weitz J, Chamberlain M, Bowie D, Barnes D, Hirsh J. Derivation of a simple model to categorize patients probability of pulmonary embolism: Increasing the model’s utility with the SimpliRED D-dimer. Thromb Haemost 2000; 83:416–20.[ISI][Medline]
5. Flanagan DEH, Creasy T, Thomas P, Cavan D, Armitage M. Computer-assisted venous occlusion plethysmography in the diagnosis of acute deep vein thrombosis. Q J Med 2000; 93:277–82.
6. Sinharay R, Strang G, Bird D. Cost effective strategy for a safe diagnosis of DVT at a district general hospital. Postgrad Med J 2003; 79: 363.
7. Tan YK, da Silva AF. Digital Photoplethysmography in the Diagnosis of Suspected Lower Limb DVT: Is It Useful? Eur J Vasc Endovasc Surg 1999; 18:71–9.[CrossRef][ISI][Medline]
8. Sinharay R. Pleuritic chest pain and hypoxia—a diagnostic dilemma. Br J Cardiol 2002; 9:589.
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