Rapid D-dimer Test Research Articles

Validation of an immunochromatographic D-dimer test to presumptively identify menstrual fluid in forensic exhibits.

Identifying the biological source of a crime scene stain can be crucial for police investigations in many scenarios. Blood is one of the most common fluids found, and accurate differentiation between peripheral blood and menstrual fluid could provide valuable information regarding the issue of consent in sexual assault cases. For the detection of menstrual fluid, no easy-to-use presumptive test is available to date. Therefore, this study aimed to validate a simple immunochromatographic test for the indication of menstrual fluid, focusing on a D-dimer assay. The Clearview® rapid D-dimer test provides a diagnostic assay for the detection of fibrin degradation products. We validated the sensitivity and robustness of the assay using fresh and dried menstrual fluid samples, body fluid mixtures, diluted samples, and casework swabs. Cross reactivity was tested for saliva, semen, vaginal fluid, and blood. No false positive results were obtained; it was possible to successfully analyze mixtures, highly diluted samples, and casework swabs. The results of this study indicate that the D-dimer assay reliably detects menstrual fluid in forensic exhibits and is easy to implement into the current workflow of body fluid identification.

Evaluation of the value of rapid D-dimer test in conjunction with cardiac troponin I test for early risk stratification of myocardial infarction

We sought to determine the diagnostic value of a D-dimer test for myocardial infarction (MI). The prospective cohort study was carried in the ED of a university hospital. All included patients were tested for D-dimer and cardiac troponin I (cTnI) on ED admission and additional cTnI 6h later. AMI was retrospectively confirmed by employing the ESC-ACC-AHA-WHF 2007 universal definition. The discriminative value of D-dimer test was assessed by ROC curve analysis. Multivariate analysis was used to identify independent risk factors associated with D-dimer elevation other than MI. A total of 178 patients were included in this study. Median D-dimer levels were significantly higher in MI patients. A D-dimer value greater than 200ng/ml was significantly associated with MI. When used alone, the test has a high sensitivity of 91.8% but a low specificity of 23.9%. Combined use of cTnI and D-dimer tests raised the sensitivity to 98.4% and helped early triage a subgroup of low risk patients. However, the test had the downside of 58% false positives. High false positives could be partly explained by the high prevalence of underlying hypercoagulable comorbidities. Diabetes mellitus with chronic renal insufficiency was identified as the strongest risk factor associated with D-dimer elevation in patients without MI. D-dimer test alone has a low diagnostic value for MI. Co-existing hypercoagulable conditions may confound the results. Combining cTnI and D-dimer tests enables early identification a low risk group of patients for MI at the cost of high false positives.

Implementation of a Rapid Whole Blood D-Dimer Test in the Emergency Department of an Urban Academic Medical Center

Overcrowding and prolonged patient length-of-stay (LOS) in emergency departments (EDs) are growing problems. We evaluated the impact of implementing a rapid whole blood quantitative D-dimer test (Biosite Triage, Biosite Diagnostics, San Diego, CA) in our ED satellite laboratory on 252 patients before vs 211 patients after implementation. All patients also underwent testing with the existing central laboratory method (VIDAS D-dimer, bioMérieux, Durham, NC). D-dimer turnaround time (from blood draw to result) decreased approximately 79% (approximately 2 hours vs 25 minutes). The mean ED LOS declined from 8.46 to 7.14 hours (P = .016). Hospital admissions decreased 13.8%, ED discharges increased 7.3%, and the number of patients admitted for observation increased 6.4% (P = .005). No difference in the utilization of radiologic studies was observed (P = .86). At 3 months' follow-up, none of the after-implementation patients with negative D-dimer results were admitted for subsequent venous thromboembolic disease. The rapid D-dimer test was associated with a shorter ED LOS and fewer hospital admissions.

Managing suspected venous thromboembolism in a mixed primary and secondary care setting using standard clinical assessment and D-dimer in a noninvasive diagnostic strategy

Venous thromboembolism is a potentially lethal disease if not properly treated. Noninvasive strategies have become an attractive clinical option for effective diagnosis. There has been controversy, however, regarding the use of standard clinical rules in a primary care setting. The objective of the present study was to validate a noninvasive diagnostic strategy in an emergency unit giving assistance to patients with primary and secondary care needs. A total of 291 outpatients (primary and secondary care needs) with suspected venous thromboembolism attending the emergency unit of a general hospital from August 2002 to 2004 were retrospectively evaluated. The diagnostic strategy included assessment of risk for venous thromboembolism and a rapid quantitative enzyme-linked immunosorbent assay D-dimer test. Venous thromboembolism was ruled out in patients with a low-probability or intermediate-probability risk (or an unlikely diagnosis) and a negative D-dimer. The prevalence of venous thromboembolism was 8.2%. Patients with an unlikely diagnosis comprised 93.8% of the evaluations for deep venous thrombosis, and those with a low probability for pulmonary embolism comprised 81.4%. Proportions of patients with venous thromboembolic events observed were 7.2% in patients with an unlikely diagnosis of deep venous thrombosis and 3.0% in those with low probability for pulmonary embolism. The percentage of patients with a thrombotic event excluded using this strategy was 37% (positive predictive value 13%, negative predictive value 100%). In conclusion, this noninvasive clinical strategy is safe for ruling out venous thromboembolism, and excludes the need for imaging tests in about one-third of the patients in the population studied.

Latex-Enhanced Immunoassay D-dimer and Blood Gases Can Exclude Pulmonary Embolism in Low-Risk Patients Presenting to an Acute Care Setting

Pulmonary embolism (PE) is common, and diagnosis is often difficult. Investigation has traditionally required expensive imaging procedures that are frequently nondiagnostic. Consequently, current practice favors noninvasive diagnosis of PE using algorithms combining risk assessment and d-dimer. Despite the proven safety of this approach, concern persists about such strategies to exclude PE, largely due to variable d-dimer sensitivity. The aim of this study was to prospectively assess the safety of a new algorithm combining a novel, rapid d-dimer test (IL Test; Instrumentation Laboratory; Lexington, MA), Pa(O2) measurement, and risk factor assessment in excluding PE in subjects presenting to an acute care setting. All patients aged 18 to 60 years presenting to the emergency department of Christchurch Hospital with suspected PE underwent measurement of d-dimer (IL Test latex-enhanced immunoassay) and Pa(O2), and were assessed for the presence of major clinical risk factors. Those with no risk factors, normal d-dimer findings, and Pa(O2) > or = 80 mm Hg (study arm A) were discharged and followed up by telephone questionnaires over 12 months. Those with elevated d-dimer levels, Pa(O2) < 80 mm Hg, or one or more risk factors (study arm B) were managed as per hospital guidelines. Outcome data were collected on these patients. Our primary outcome was incidence of PE in group A during the first 3-month follow-up period. Three hundred twenty-eight patients were enrolled, of whom 149 were assigned to group A and 179 were assigned to group B. In none of the group A patients was PE diagnosed over the subsequent 3-month period (0%; 95% confidence interval, 0 to 2.1%). PE was diagnosed in 37 group A patients (21%). The latex-enhanced immunoassay d-dimer and normal arterial oxygen pressure levels can safely exclude PE in a low-risk population presenting to an acute care setting. While these results cannot be extrapolated to all patients with suspected PE, they do confirm the safety of this approach in a population with a low underlying risk of PE.

Review: a low clinical probability plus a normal D-dimer test result excludes a diagnosis of deep venous thrombosis

Fancher TL, White RH, Kravitz RL. Combined use of rapid D-dimer testing and estimation of clinical probability in the diagnosis of deep vein thrombosis: systematic review. BMJ 2004;329:821. [OpenUrl][1][Abstract/FREE Full...

Review: a low clinical probability plus a normal d-dimer test result excludes a diagnosis of deep venous thrombosis

Fancher TL, White RH, Kravitz RL. Combined use of rapid d-dimer testing and estimation of clinical probability in the diagnosis of deep vein thrombosis: systematic review. BMJ 2004;329:821.[OpenUrl][1][Abstract/FREE Full Text][2]...

Evidence for Safe Exclusion of Deep Vein Thrombosis (DVT) by a Rapid ELISA D-Dimeer Test at Cut-Off Levels of 500 and 1000 Ng/Ml in 1046 Consecutive Outpatients with Suspected DVT.

Introduction.A normal compression ultrasonography (CUS) safely excludes proximal deep vein thrombosis (DVT) with a negative predictive value of 97% indicating the need to repeat CUS testing within one week. In 3 studies, the rapid ELISA D-dimer assay at a cut-off of 500 ng/ml did have a sensitivity of 100% for the exclusion of venographically documented distal and proximal DVT irrespective of clinical score. To test this hypothesis we performed a large prospective study in outpatients with suspected DVT.Methods. CUS and a rapid ELISA D-Dimer test (VIDAS, BioMérieux L'Etoile, France) were performed in patients with suspected DVT. A negative CUS with a D-Dimer result of <500 ng/ml exclude DVT, and with a D-Dimer result of >500 ng/ml was followed by a second CUS within one week.Results. The prevalence of DVT 1046 consecutive out patients with suspected DVT was 23,4%. The first CUS was positive in 228 with a rapid ELISA D-Dimer of >500 ng/ml in 227 and of <500 ng/ml in one case, indicating a sensitivity of 99,6% irrespective of clinical score. The first CUS was negative in 818. The rapid ELISA D-dimer test Was <500 ng/ml in 297 of which 296 had a negative first CUS indicating a negative predictive value of 99.7% at a specificity of 37% irrespective of the clinicl score. The negative predictive value of a negative CUS plus a rapid ELISA D-Dimer result of less than 1000 ng/ml is 99.5% at a specificity of 67,9% irrespective of clinical score. The prevalence of DVT in patients with negative first CUS and a ELISA D-Dimer of >1000 ng/ml was 5.6% as documented by CUS repeat within on week.Conclusion.A normal rapid ELISA D-dimer test, <500 ng/ml, in outpatients with suspected DVT safely excludes DVT irrespective of clinical score. After a negative rapid ELISA result (<500 ng/ml), CUS is still indicated for safety reasons in patients with suspected DVT and persistent symptoms in search for an alternative diagnosis, or for a rare case of DVT. A negative CUS plus and ELISA D-Dimer result of <1000 ng/ml safely exclude DVT without the need to repeat CUS in 2/3 of patients with a negative first CUS.

Combined use of rapid D-dimer testing and estimation of clinical probability in the diagnosis of deep vein thrombosis: systematic review

Objective To summarise the evidence supporting the use of rapid D-dimer testing combined with estimation of clinical probability to exclude the diagnosis of deep venous thrombosis among outpatients.Data sources Medline...

Rapid D-dimer test combined a clinical model for deep vein thrombosis. Validation with ultrasonography and clinical follow-up in 383 patients.

An optimal approach to the diagnosis of deep vein thrombosis (DVT) in lower limbs in the emergency department is still unknown. In this prospective cohort study, we aimed to evaluate the accuracy of the widely available plasma D-dimer test (VIDAS) and establish the usefulness of combining D-dimer testing with a clinical model to reduce the need for serial ultra-sonographies and improve the diagnostic strategy of DVT. We performed a cohort study in 383 consecutive outpatients referred to the emergency department of Hospital La Princesa, with clinical suspicion of DVT. The patients were stratified into three pre-test probability categories using an explicit clinical model (Wells score), and underwent a quantitative automated ELISA D-dimer assay (VIDAS D-Dimer bioMérieux). Patients were managed according to the diagnostic strategy based on clinical probability and compression ultrasonography (CU). Patients for whom DVT was considered a high pre-test probability with negative ultrasonographic findings in the initial CU, returned the following week for repeat ultrasonography. All patients with DVT excluded did not receive anticoagulant therapy, and were followed up for three months to monitor the development of venous thromboembolic complications. DVT was confirmed in 102 patients (26.6%): 95 in the initial test, four in the second test, and three who developed venous thromboembolic complications in the three-month follow-up period. The calculated D-dimer cut-off level was 1 micro g/ml. One hundred patients (98%) with DVT had positive D-dimer. D-dimer had a sensitivity of 98% and a negative predictive value of 98.6%. Among the high-probability patients with positive D-dimer tests and initial negative CU, 9.75% had DVT on repeat CU at one week. The study results suggest that the addition of VIDAS D-dimer to this diagnostic algorithm could improve the management of patients with suspected DVT in daily practice. A diagnostic approach of DVT based on D-dimer (cut-off > or =1 microg/ml) as the first diagnostic tool for the exclusion of DVT, and the clinical probability model as the tool that identifies those patients requiring a second ultrasonography is useful and suitable for daily medical practice.

The clinical usefulness of D-dimer testing in cancer patients with suspected deep venous thrombosis.

Little is known about the diagnostic value of a D-dimer test in cancer patients with clinically suspected deep venous thrombosis (DVT). To evaluate the clinical utility of a whole blood rapid D-dimer test (SimpliRED) in cancer patients compared with noncancer patients. In consecutive patients with suspected lower limb DVT, a D-dimer test and ultrasonogram were performed. Cancer status was recorded at presentation. If the D-dimer test and ultrasonogram results were normal, DVT was considered absent. If the D-dimer result was abnormal, ultrasonography was performed again 1 week later. Anticoagulant therapy was only instituted in those patients with an abnormal ultrasonography result. All patients were followed up for 3 months to record subsequent thromboembolic events. The accuracy of the D-dimer test was assessed, and the efficiency and safety of withholding additional ultrasonography in cancer patients with normal results on both D-dimer and ultrasonography was compared with noncancer patients. A total of 1739 consecutive patients were studied, 217 (12%) of whom had cancer. The negative predictive value of the D-dimer test was 97% in both cancer and noncancer patients. In 63 (29%) of all 217 cancer patients, the D-dimer and ultrasonography results were normal at referral; therefore, the diagnosis of DVT was refuted and anticoagulant treatment was withheld. In these 63 patients, one thromboembolic event occurred during follow-up (1.6%; 95% confidence interval, 0.04%-8.53%). The negative predictive value of a whole blood D-dimer test in cancer patients seems as high as in noncancer patients. In a substantial proportion of cancer patients, the diagnosis can likely be refuted at referral, based on normal D-dimer test and ultrasonogram results. Furthermore, it seems safe to withhold anticoagulant therapy in these patients.

Clinical prediction of deep venous thrombosis using two risk assessment methods in combination with rapid quantitative D-dimer testing

Purpose The optimal approach to diagnosing deep venous thrombosis is not entirely clear. In this prospective cohort study, we aimed to evaluate the yield of two methods of assessing the pretest probability of deep venous thrombosis—the treating physician’s implicit assessment and the Wells score, a validated prediction rule that incorporates signs, symptoms, and the presence or absence of an alternative diagnosis—used in isolation and in combination with D-dimer measurement. Subjects and methods We studied 278 patients who were referred for suspicion of deep venous thrombosis. All patients were stratified into groups of low, moderate, or high risk of deep venous thrombosis on the basis of the clinical assessment and Wells score, and underwent rapid quantitative D-dimer testing (with a cutoff of 500 μg/mL), ultrasound examination, and follow-up for the occurrence of venous thromboembolism. Results Eighty-two patients (29%) had a deep venous thrombosis. The accuracy of both methods was good (area under the receiver operating characteristic curve = 0.72), despite only fair agreement at the level of individual patients (weighted kappa = 0.31; 95% confidence interval [CI]: 0.23 to 0.40). The negative predictive value of D-dimer measurement was 96% (95% CI: 91% to 100%). When restricted to patients with low pretest probability, the negative predictive value of D-dimer measurement was 100% (95% CI: 96% to 100%) with the use of the Wells score and 96% (95% CI: 88% to 100%) with the physician’s assessment. Our results were unchanged in analyses restricted to patients with proximal deep venous thrombosis or outpatients. Conclusion Clinical assessment to stratify a patient’s likelihood of having deep venous thrombosis should be taught to physicians.

Validation of the Canadian Clinical Probability Rule and Use of Bedside D-Dimer Testing in the Diagnosis of Acute Venous Thrombosis in an Emergency Room Setting

PURPOSE: To validate the Canadian clinical probability tool and utility of bedside rapid D-dimer testing using SimpliRed® among patients with suspected acute deep-vein thrombosis (DVT) in an emergency room setting. METHODS: Consecutive patients with clinically suspected DVT in a leg and no past history of symptomatic DVT were evaluated in the UC Davis emergency room by emergency room staff using the clinical probability tool developed by Wells and colleagues [Lancet,1997; 350:1795], which was provided on a one page form. After completing the form, each patient underwent venous ultrasound (US) imaging, whole blood D-dimer testing using SimpliRed®, and D-dimer measurement using a sensitive ELISA technique. All patients were followed for 3 months. Diagnosis of thromboembolism required objective confirmation of DVT using US or venography, or confirmation of pulmonary embolism using a high-probability lung scan or pulmonary arteriography. RESULTS: Of 102 patients who were evaluated, 17 (17%) were diagnosed as having DVT initially; none of the 85 in whom DVT was excluded developed thromboembolism within 3 months. Ten of 17 (59%, CI 36%–82%) who met criteria for ‘high-probability’, 6 of 44 (13%, CI 5%–21%) with ‘intermediate probability’ and 1 of 41 (2.4%, CI 0.5%–7%) with ‘low probability’ had objectively confirmed DVT. This compares to published values of 49%, 14% and 3%, respectively, from two Canadian emergency rooms. Forty-one of the 102 (40%) patients had an ‘alternate diagnosis as likely or greater than DVT’, which lowered the probability of DVT by one or more levels in 35 (85%) cases. Thirty-eight of the 41 (93%) patients with an ‘alternate diagnosis’ did not have DVT; the 3 who did have DVT were thought to have cellulitis (n = 2) or knee hyperextension (n = 1). The negative predictive value of the SimpliRed rapid D-dimer test was 100%, 100% and 71% (5 of 7) in the low, intermediate and high probability groups. Both ‘false negative’ SimpliRed® tests had normal levels of D-dimer using a sensitive ELISA method, and careful re-review of the US studies revealed findings consistent with subacute or chronic DVT. CONCLUSION: The Canadian probability tool for DVT appears to be a valid instrument in our emergency department. Similarly, we documented the high negative predictive value of bedside D-dimer (SimpliRed®) testing among patients classified as ‘low’ or ‘intermediate’ probability for having DVT, as reported in the literature. Radiographic misinterpretation of subacute or chronic DVT as acute DVT may partially explain the lower negative predictive value of SimpliRed® testing in patients with high clinical probability of having DVT.

A negative d-dimer result and low risk clinical status effectively ruled out DVT in symptomatic patients

(1999) J Vasc Surg 30, 929; Aschwanden M, Labs KH, Jeanneret C, et al. . The value of rapid d-dimer testing combined with structured clinical evaluation for the diagnosis of...

Rapid ELISA D-dimer testing in the exclusion of venous thromboembolism in hospitalized patients.

The clinical diagnosis of deep-vein thrombosis (DVT) and pulmonary embolism (PE) is known to be unreliable. Until now, no biological marker has been found to confirm thrombosis, but help can be gained from a biological marker ruling out the diagnosis of DVT or PE, i.e., the sensitive measurement of D-dimer (DD) species. This article summarizes our experience in introducing a rapid D-dimer test (ELISA VIDAS D-dimères test, bioMérieux) in a collaborative strategy for thrombosis diagnosis during 9 consecutive months involving 1,131 measurements. The efficacy of the DD test was very different according the type of patient, and departments where the DD test provides a real diagnostic benefit were identified. High clinical probability for thrombosis was encountered in 32 patients and radiology was carried out, although D-dimer was negative: none of these patients was found to have a thrombosis after radiologic examination. However, extensive progress must be made in test prescription to reduce the excessive rate of positive D-dimer tests (78%) and positive measurements that are not followed up by radiology (42%).

Exclusion and diagnosis of pulmonary embolism by a rapid ELISA D-dimer test and noninvasive imaging techniques within the context of a clinical model.

A negative rapid ELISA D-dimer test alone in out-patients with a low to moderate clinical probability (CP) on pulmonary embolism (PE) is predicted to safely exclude pulmonary embolism. The combination of a negative rapid ELISA D-dimer test and a low to moderate CP on PE followed by compression ultrasonography (CUS) for the detection of deep vein thrombosis (DVT) is safe and cost-effective as it reduces the need for noninvasive imaging techniques to about 50% to 60% of outpatients with suspected PE. A high probability ventilation-perfusion (VP) scan or a positive spiral CT consistent with PE and the detection of DVT by CUS are currently considered to be clear indications for anticoagulant treatment. Subsequent pulmonary angiography (PA) is the gold standard diagnostic strategy to exclude or diagnose PE in suspected outpatients with a negative CUS, a positive rapid ELISA D-dimer test, and a nondiagnostic VP scan or negative spiral CT to prevent overtreatment with anticoagulants. However, the willingness of clinicians and the availability of resources to perform PA is restricted, a fact that has provided an impetus for clinical investigators to search for alternative noninvasive strategies to exclude or detect venous thromboembolism (VTE). Serial CUS testing for the detection of DVT in patients with a low to moderate CP on PE and a nondiagnostic VP scan or negative spiral CT is predicted to be safe and will reduce the need for PA to less than 10% or even less than 5%. This noninvasive serial CUS strategy restricts the need for invasive PA to a minor group of patients (< 5%) with the combination of a low CP on PE and high probability VP scan or the combination of a nondiagnostic VP scan or negative spiral CT and a high CP on PE. Prospective evaluations are warranted to implement and to validate the advantages and the disadvantages of the various combinations of noninvasive strategies and to compare serial CUS testing versus PA in randomized clinical management studies of outpatients with suspected pulmonary embolism.

Strategies for the safe and effective exclusion and diagnosis of deep vein thrombosis by the sequential use of clinical score, D-dimer testing, and compression ultrasonography.

Patients with suspected deep vein thrombosis (DVT) are subjected to leg vein compression ultrasonography (CUS) that confirms DVT in only 20 to 30% of patients. A positive CUS is consistent with DVT irrespective of clinical score. The sequential use of a simple clinical score assessment, a rapid sensitive enzyme-linked immunosorbent assay (ELISA) D-dimer test and CUS to safely exclude DVT is promising. The clinical score is a validated clinical model of complaints, signs, and symptoms, on the basis of which a pretest clinical probability for 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 or CUS necessitates a negative predictive value of more than 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 to 10%, 15 to 30% and more than 70%, respectively. A negative rapid ELISA D-dimer and a low clinical score (prevalence DVT 3 to 5%) will have a very high negative predictive value of more than 99.5% to exclude DVT without the need of CUS testing. A negative ELISA D-dimer test and a first-negative CUS safely exclude DVT in patients with a moderate clinical score with a negative predictive value of more than 99.5%, therefore obviating the need to repeat CUS. The use of a rapid ELISA D-dimer testing in patients with a high clinical score is not recommended. A negative CUS, a low clinical score, and a positive ELISA D-dimer, even less than 1000 ng/mL exclude DVT with a nega tive predictive value of more than 99%. Patients with a negative CUS, but a positive ELISA D-dimer, and a moderate or high clinical score have a probability of DVT of 3 to 5% and 20 to 30%, respectively, and are thus candidates for repeated CUS testing. The proposed sequential use of the clinical score assessment, a rapid ELISA D-dimer test, and CUS will be the most cost-effective diagnostic strategy for DVT because of a significant reduction of CUS examinations and gain of time for the patient and physician in charge.

Rapid ELISA Assay for Plasma D-Dimer in the Diagnosis of Segmental and Subsegmental Pulmonary Embolism

To assess the accuracy of a rapid ELISA D-dimer assay for the exclusion of pulmonary embolism (PE) in patients suspected of PE, using pulmonary angiography alone as reference method rather than a diagnostic strategy including lung scintigraphy and leg vein ultrasonography. In 342 patients who were examined by pulmonary angiography to diagnose or exclude PE, the accuracy of the quantitative rapid VIDAS D-dimer test for the exclusion of PE was evaluated retrospectively. D-dimer levels were assayed in frozen samples collected during the diagnostic work-up at the time of pulmonary angiography while on treatment with unfractionated heparin for 1-2 days. Mean plasma D-dimer concentrations were increased in patients with angiographic evidence of PE (P <0.0001). The sensitivity of D-dimer for segmental PE was 98%, its accuracy in excluding segmental PE was 99%, higher than the respective figures for subsegmental PE (76% and 94%; P <0.01, both). For both forms of PE combined the sensitivity was 90% and the negative predictive value 94%. The sensitivity and negative predictive values reported here, are low compared with previous studies using the same rapid ELISA D-dimer assay. This probably reflects an overlooking of mild cases of subsegmental PE in previous studies, although a reduction of D-dimer levels by the heparin pretreatment may have contributed to part of the discrepancy. Prospective studies are needed to clarify this issue.

Combination of a clinical risk assessment score and rapid whole blood D-dimer testing in the diagnosis of deep vein thrombosis in symptomatic patients

Purpose: The clinical diagnosis of deep vein thrombosis (DVT) is unreliable in more than 50% of cases, and, in recent years, plasma D-dimer assays have been used to predict the presence of DVT with high sensitivity and negative predictive values. This study investigated the use of a rapid whole blood test that could be performed and interpreted by the bedside in addition to a clinically derived risk assessment score (RAS) to determine whether a practical and cost-effective clinical model could be developed for the diagnosis and exclusion of DVT in symptomatic patients. Methods: Two hundred consecutive patients who were referred to the vascular laboratory with clinically suspected DVT underwent the following procedures: (1) clinical assessment and stratification into low, moderate, or high risk for DVT on the basis of an RAS related to history, symptoms, and physical examination findings; (2) rapid (5-minute) whole blood D-dimer testing with a semi-qualitative agglutination technique on a fingerprick blood sample; and (3) color flow duplex ultrasound scanning with standard criteria for the diagnosis of proximal and calf DVT. Results: Forty-six patients (23%) had acute DVT on duplex ultrasound scanning. Of these cases, 28 (61%) had proximal DVT and 18 (39%) were confined to the calf. A total of 88 patients were classified as low risk, 67 were classified as moderate, and 45 were classified as high risk on the basis of the RAS method. Of the patients who were classified at low risk, 4.5% (4/88) had DVT, as compared with 17.9% (12/67) in the moderate clinical risk group and 66.7% (30/45) in the high risk group. Isolated calf DVT was found in 30% (9/30), 50% (6/12), and 75% (3/4) of the high, moderate, and low risk groups, respectively. The sensitivity (8.7%, 26.1%, 65.2%), specificity (45.5%, 64.3%, 90.3%), positive predictive value (4.5%, 17.9%, 66.7%), and overall accuracy rate (37%, 55.5%, 84.5%) of the low, moderate, and high risk groups, respectively, in the diagnosis of DVT increased significantly with increasing risk score stratification. The sensitivity, specificity, positive and negative predictive value, and overall accuracy of the rapid D-dimer test for all DVT were 91.3%, 81.9%, 60%, 96.9%, and 84%, respectively, with a 100% sensitivity and negative predictive value for proximal DVT. A combination of the RAS and D-dimer identified a low risk group with a negative D-dimer as having less than a 1% likelihood of DVT and a high risk group with positive D-dimer as having a likelihood of more than 90%. Conclusion: A combination of clinical assessment and rapid D-dimer testing provides an effective means of excluding proximal DVT in symptomatic patients. The application of a clinical diagnostic model on the basis of these parameters has the potential for saving a large proportion of unnecessary duplex scans with the associated time and costs. (J Vasc Surg 1999;30:794-804.)

The value of rapid D-dimer testing combined with structured clinical evaluation for the diagnosis of deep vein thrombosis

Purpose: Large studies have shown that most cases referred for duplex sonography for suspected deep vein thrombosis (DVT) have normal scan results. For medical and economic reasons, a preselection procedure, which allows the detection of true-negative cases before duplex scanning, is required; this procedure should be characterized by a high sensitivity and a high negative predictive value. Methods: In 343 patients (398 lower extremities) with suspected DVT, the DVT probability was clinically assessed, and a whole blood D-dimer agglutination test and a duplex scan were performed. The diagnostic sensitivities of the D-dimer test alone, a high clinical DVT probability alone, and the combination of both were evaluated. Results: The sensitivity values for the D-dimer test to diagnose proximal and distal DVTs were 88.7% and 80.9%, the negative predictive values (NPV) were 96.3% and 97.9%, and the specificity and the positive predictive value (PPV) were 54.8% and 49.6% and 26.6% and 8.2%, respectively. The sensitivities of the clinical DVT probability assessment for the diagnosis of proximal and distal DVTs were 83.9% and 66.7%, respectively; the corresponding NPVs were 94.9% and 96.5%, respectively. The specificity was 56.1% and 50.8%, and the PPVs were 26.1% and 7.0%, respectively. The combined use of the results of the clinical probability assessment and the D-dimer test resulted in sensitivities for proximal and distal DVTs of 98.4% and 90.5%, NPVs of 99.3% and 98.6%, a specificity of 43.4% and 38.4%, and PPVs of 24.3% and 7.6%, respectively. Conclusion: The combined use of a clinical DVT probability assessment scheme and the D-dimer test largely avoids false negative results, has a high sensitivity and NPV, helps to reduce the costs of DVT diagnosis, and may, in the future, be useful as a preselection procedure before duplex sonography. (J Vasc Surg 1999;30:929-35.)