Phlebography, compression ultrasonography, D-dimer and clinical score: Which approach for which case of suspected deep vein thrombosis (DVT)
Faculty of Medicine and Health Sciences
University Hospital Antwerp
Bologna :Medimond, 2001
14th Congress of the European-Chapter of the, International-Union-of-Angiology, May 23-26, 2001, Cologne, Germany
University of Antwerp
Flebography is the reference gold standard for the exclusion and diagnosis of proximal deep vein thrombosis (DVT) and calf vein thrombosis (CVT). A negative flebogram excludes both proximal DVT and CVT, but due to its invasive nature and associated side effects it has been replaced by compression ultrasonography (CUS). Patients suspicious of DVT are subjected to leg vein compression ultrasonography (CUS) that actually confirms DVT in only 16 to 28% of outpatients in large prospective management studies. CUS has a high positive predictive value of more than 98% for proximal DVT and usually overlooks calf vein thrombosis. Therefore a positive CUS is consistent with proximal DVT irrespective of clinical score. The negative predictive value of CUS for proximal DVT is about 97-98%, on the basis of which repeated CUS testing at day 7 after a negative 1(st) CUS (serial CUS) in outpatients with a 1(st) suspicion on DVT is advocated. Serial CUS testing appears to be ineffective and costly. The diagnostic strategy of DVT can be simplified and improved by the combined use of clinical score, D-dimer testing and CUS. The clinical score is a validated model of complaints, signs and symptoms on the basis of which a pretest clinical probability on DVT can be estimated as low, moderate and high. The safe exclusion of DVT by a rapid sensitive D-dimer test in combination with clinical score and/or CUS requires a negative predictive value of > 99%. The negative predictive value for DVT is determined by the sensitivity of the rapid ELISA D-dimer test and the prevalence of DVT in subgroups of outpatients with suspected DVT. The prevalence of DVT in outpatients with a low, moderate and high clinical score varies widely from 3-10%, 15-30% and > 70% respectively. The combination of low clinical score (prevalence DVT 3-5%) and a negative rapid ELISA D-dimer alone test will have a very high negative predictive value of > 99.9% to exclude DVT without, the need of CUS testing. The combination of both a negative ELISA D-dimer test and a V negative CUS win exclude DVT in patients with a moderate clinical score with a negative predictive value of > 99.5%, thus obviating the need to repeat CUS. The combination of a negative CUS and a negative rapid ELISA D-dimer test safely excludes DVT in patients with suspected DVT irrespective of clinical score. A negative CUS, a low clinical score and a positive ELISA D-dimer but < 1000 ng/ml still exclude DVT with a negative predictive value of > 99% without the need to repeat CUS. Patients with a negative CUS, but a positive ELISA D-dimer, and a moderate or high clinical score are still at risk with a probability on DVT of 3-5% and 20-30% respectively and thus candidates for repeated CUS testing. The rapid ELISA D-dimer first followed by risk-based no or single CUS will be the most cost/effective strategy.