Clinical assessment of suspected deep vein thrombosis: comparison between a score and empirical assessment.

OBJECTIVES: To assess the accuracy and agreement of two methods of clinical evaluation: a formal score based on a number of items of fixed value (the so-called Wells' score), and an empirical assessment based on a predefined list of items that can be weighted individually. Clinical probability is essential to manage suspected deep vein thrombosis (DVT) and should be assessed before any diagnostic test.

DESIGN: An open, nonrandomised, one-centre study.

SETTING: One centre in Switzerland (a university hospital delivering primary-tertiary care).

SUBJECTS: Two hundred and seventy outpatients with a prevalence of DVT of 21.1% (final diagnosis), out of an initial population of 328 patients, of which 52 had to be excluded because of a history of DVT (score not applicable) or because of insufficient clinical information (n = 6).

RESULTS: Agreement between the two assessment tools was poor (kappa value of 0.32), but accuracy was excellent, with a prevalence of DVT of 1.3%, 18.1%, and 100% (empirical assessment), and 3.2%, 19.4%, and 73.9% (Wells' score), for a low, intermediate or high clinical probability estimate, respectively. The main differences between the two methods were that (i) the empirical method performed slightly better in categorizing patients in the high probability class, and (ii) Wells' score categorized more patients in the low probability class. When applied to two validated diagnostic strategies, the empirical assessment required slightly fewer phlebograms in both strategies, and Wells' score required fewer repeat ultrasonograms (in the strategy that requires this procedure).

CONCLUSIONS: Clinical probability assessment can be done with a similar accuracy either empirically or using a score. Institutions should incorporate clinical probability assessment with either method depending upon their diagnostic strategy for suspected DVT.