Accuracy in diagnosing deep and pelvic vein thrombosis in primary care: an analysis of 395 cases seen by 58 primary care physicians.

BACKGROUND

Ruling out a deep vein thrombosis (DVT) is difficult in general practice because the clinical manifestations of DVT are nonspecific and more often due to other diseases. The aim of diagnostic screening in primary care must be to rule out a DVT with high accuracy in most patients, so that only those who are likely to have a DVT will undergo further testing. In this study, we tested the accuracy of exclusion of DVT by the combination of a clinical score (the Wells score) with either a bedside D-dimer test or selective compression sonography.

METHOD: This cohort study included all patients who presented to the participating primary care physicians and were suspected of having a DVT on the basis of pre-defined inclusion criteria. To rule out DVT, a Wells score was determined for all patients, and all patients additionally underwent either a D-dimer test or selective compression sonography as required by the clinical algorithm. Patients were seen six weeks later in follow-up to determine whether they had actually had a DVT (gold standard). The negative predictive value (NPV) for the exclusion of DVT in this way was determined, as was the NPV of clinical judgment alone, without knowledge of Wells score or D-dimer results.

RESULTS

395 patients were evaluated by 58 primary care physicians for suspected DVT; 59 were ultimately found to have had a definite DVT, and 9 a probable DVT. Exclusion of DVT with the study protocol had an NPV of 99.0% (95% CI, 96.3 to 99.8)-i.e. only one case of DVT in 100 patients was missed (maximum: 4, minimum: 0)-while clinical judgment alone had an NPV of 95.0% (95% CI, 90.7 to 97.7).

CONCLUSION

We recommend the Wells score combined with either a D-dimer test or selective compression sonography according to the algorithm used in this study for use in primary care to rule out DVT. Clinical judgment alone is less effective.