Negative D-dimer Test Research Articles

Sensitivity and specificity of a rapid whole-blood assay for D-dimer in the diagnosis of pulmonary embolism.

Patients with suspected pulmonary embolism often have nondiagnostic lung scans and may present in circumstances where lung scanning is unavailable. Levels of D-dimer, a fibrin-specific product, are increased in patients with acute thrombosis; this may simplify the diagnosis of pulmonary embolism. To determine the sensitivity and specificity of a whole-blood D-dimer assay in patients with suspected pulmonary embolism and in subgroups of patients with low pretest probability of pulmonary embolism or nondiagnostic lung scans. Prospective cohort. Four tertiary care hospitals. 1177 consecutive patients with suspected pulmonary embolism. All patients underwent an assessment of pretest probability by use of a standardized clinical model, a D-dimer assay, ventilation-perfusion lung scanning, and bilateral compression ultrasonography. Patients in whom pulmonary embolism was not initially diagnosed were followed for 3 months. Accordingly, patients were categorized as positive or negative for pulmonary embolism. Of the 1177 patients, 197 (17%) were classified as positive for pulmonary embolism. Overall, the D-dimer assay showed a sensitivity of 84.8% and a specificity of 68.4%. In 703 patients (3.4%) with a low pretest probability of pulmonary embolism, the likelihood ratio associated with a negative D-dimer test result was 0.27, resulting in a posterior probability of 1.0% (95% CI, 0.3% to 2.2%). In 698 patients with nondiagnostic lung scans (previous probability, 7.4%), the likelihood ratio associated with a negative D-dimer test result was 0.36, resulting in a posterior probability of 2.8% (CI, 1.4% to 4.8%). A normal D-dimer test result is useful in excluding pulmonary embolism in patients with a low pretest probability of pulmonary embolism or a nondiagnostic lung scan.

The cost-effectiveness of diagnostic strategies in patients with suspected pulmonary embolism.

The cost-effectiveness of various diagnostic strategies in patients with clinically suspected pulmonary embolism (PE) was analysed using a modelling approach. In 451 consecutive patients with clinically suspected PE data on the performance of diagnostic tests were collected prospectively in two large teaching hospitals in Amsterdam, The Netherlands. The ventilation-perfusion lung scan was used as the primary diagnostic test in all patients. In patients with a non-diagnostic lung scan result the performance of a clinical decision rule, a D-dimer test, and ultrasonography of the leg veins was evaluated with pulmonary angiography as the gold standard. It was estimated that the strategy recommended by a 1992 Dutch consensus meeting costs about Dfl 4400 per patient and that 97.02% of the patients can be expected to survive the first 6 months after the primary PE. The nation-wide annual costs for the diagnosis and treatment of patients by this strategy were estimated at 163 million Dutch Guilders. Subsequently, the costs and effects of alternative strategies were evaluated in a modelling approach, and compared with those of the consensus strategy. One strategy was selected that produces the best results in terms of survival and leads to considerable savings as compared with the consensus strategy. In this strategy subsequently a ventilation-perfusion scan, a clinical decision rule, a D-dimer test, a pulmonary angiography and leg ultrasonography are performed. Patients with a high probability ventilation-perfusion scan, an abnormal angiography or leg ultrasound test are treated, whereas treatment is withheld in patients with a normal ventilation-perfusion scan, a normal clinical decision rule, a negative D-dimer test, a normal angiography, or a normal leg ultrasound test. This strategy will have to prove its value and usefulness in clinical practice in a subsequent prospective validation phase.

Evaluation of a New Rapid Quantitative D-dimer Assay in Patients with Clinically Suspected Deep Vein Thrombosis

The sensitivity and specificity for deep vein thrombosis (DVT) of a new rapid, quantitative and precise (total imprecision < 10%) D-dimer assay suitable for individual measurements (VIDAS D-DIMER, bio-Mérieux, France) were evaluated in a consecutive series of 103 in- and out-patients submitted to serial compression ultrasonography (C-US) for the clinical suspicion of DVT (n = 66) or of DVT recurrence (n = 37) and symptoms lasting from 1 to 15 days. DVT was found in 22 patients at baseline testing and no patient with an initially negative C-US developed vein incompressibility at follow up. The time elapsed from the onset of symptoms was negatively associated with D-dimer levels both in patients with and in those without DVT. In the entire series of patients, the sensitivity of a positive D-dimer test ( > or = 1.0 microgram/ml) for the presence of DVT was 96% (21/22 patients, 95% confidence interval 75-100%) with a specificity of 75% (64-84%), a negative predictive value of 98% (90-100%), a positive predictive value of 51% (35-67%), and an overall accuracy of 80% (70-87%). A normal D-dimer value (0.22 microgram/ml) was observed in one patient with DVT and symptoms lasting from 15 days. The approach of withholding C-US testing in patients with symptoms lasting from less than 11 days and D-dimer levels below the cut-off value was compared to serial C-US testing alone in a cost-effectiveness analysis subdividing the 66 patients with a first episode according to their clinical pretest probability of DVT. Thrombosis was detected in 6.7% of the patients in the low probability group (n = 15), 16.7% of the patients in the moderate probability group (n = 24), 51.9% of the patients in the high probability group (n = 27) and 8.1% of patients with suspected DVT recurrence. Calculated cost-savings for each DVT diagnosed ranged from 5% in the high pretest probability group to 55% in the low pretest probability group and to 77% in patients with suspected DVT recurrence. The safety of avoiding C-US testing in symptomatic patients with a negative D-dimer test should be evaluated in clinical management studies.

Assessment of D-dimer measurement by ELISA or latex methods in deep vein thrombosis diagnosed by ultrasonic duplex scanning

In 100 consecutive patients with clinically suspected deep vein thrombosis (DVT) of the legs, plasma D-dimer measurements based on an enzyme linked immunosorbent assay (ELISA) and on latex agglutination (Diagnostica Stago) were compared to the results of real time B mode ultrasound imaging combined with Doppler examination, which in a previous study has proved to be a very accurate method competitive with venography for the diagnosis of DVT. Forty five patients had DVT identified with the ultrasonic tests. We have obtained for ELISA and latex tests of D-dimer respectively: accuracy: 60%, 56%; sensitivity: 98%, 98%; specificity: 29%, 22%; predictive value of a positive test: 53%, 50% and predictive value of a negative test: 94%, 92%. These results confirmed those of previous studies using ELISA or latex assays, with venography as a reference test. We conclude that a negative D-dimer test, defined by a value lower than 0.5 μg/ml, excludes the diagnosis of DVT in 94% of cases by ELISA method and in 92% of cases by latex method. A reduction of venography or other objective testing of the venous circulation could be obtained if these methods were not performed in the case of a negative D-dimer test. However the safety of withholding anticoagulant therapy in out patients with negative tests needs confirmation in a prospective trial.