Normal D-dimer levels in cancer patients with radiologic evidence of pulmonary embolism.

Accurate and expeditious diagnosis and treatment of pulmonary embolism in cancer patients improves patient outcomes. D-dimer is often used to rule out pulmonary embolism. However, this test is less accurate in cancer patients, and it is unclear whether cancer patients with normal D-dimer levels can present with pulmonary embolism. All consecutive patients who presented to The University of Texas MD Anderson Cancer Center in Houston, Texas, USA, between May 2009 and November 2015 who underwent computed tomography pulmonary angiography and plasma D-dimer level measurement were retrospectively reviewed. Patients with suspected pulmonary embolism and normal D-dimer levels were identified. Among the 8023 cancer patients identified, 1156 (14%) had pulmonary embolism. Only 35 patients with pulmonary embolism (3%) had normal plasma D-dimer levels. Twenty-six of these patients had acute pulmonary embolism and the other nine had subacute or chronic pulmonary embolism. Thirteen of the 26 acute cases were in patients with hematological cancer. Most patients (23/35, 66%) had subsegmental or segmental pulmonary embolism. Only one patient had pulmonary embolism in the main pulmonary arteries. Although it is uncommon (3%), cancer patients with radiologic evidence of pulmonary embolism can present with normal D-dimer levels. Recognizing the possibility of this uncommon occurrence is critical in the decision process for ordering diagnostic tests for evaluation of suspected pulmonary embolism.

Effects of storage and thawing conditions on coagulation testing.

INTRODUCTION: Current recommendations for coagulation testing storage and thawing are based on historical studies that were performed using unbuffered 3.8% sodium citrate. We sought to measure the effects of freezing and thawing conditions 3.2% buffered sodium citrate plasma samples that have been stored in vials with either snap or sealed screw tops, frozen in -70 °C freezer or dry ice and thawed either capped or uncapped. METHODS: Shed blood samples were pooled and then aliquoted into four snap top and four screw tops vials. Half the vials were stored in a -70 °C freezer, and half on dry ice for at least 16 h. Afterwards, half the frozen samples were thawed in 37 °C waterbath capped, and other half were thawed capped. After thawing cycles, samples were tested for PT, activated partial thromboplastin time (APTT), fibrinogen, D-dimer, factor assays, von Willebrand factor activity, plasminogen, antithrombin, protein C and lupus anticoagulant. RESULTS: Prothrombin time, APTT, factor X, and lupus anticoagulant testing were affected by all vials, freezing and thawing conditions, whereas fibrinogen, D-dimer, von Willebrand activity or protein C were not affected by any vial, freezing or storage condition. CONCLUSIONS: Storage vials, freezing and thawing condition affect coagulation testing, although these differences may not be clinically significant.

Evaluation of the diagnostic performance of fibrin monomer in disseminated intravascular coagulation.

BACKGROUND: Fibrin-related markers (FRM) such as fibrin monomer (FM) and D-dimer (DD) are considered useful biological markers for the diagnosis of disseminated intravascular coagulation (DIC). However, no studies on the diagnostic performance of different FRMs have been published in Korea. The aim of this study was to evaluate the diagnostic performance of FM for DIC in comparison with DD. METHODS: The reference limit of FM was determined based on plasma sample data obtained from 210 control individuals. To evaluate diagnostic performance, FM data from the plasma samples of 139 patients with DIC-associated diseases were obtained for DIC scoring. FM was measured by immunoturbidimetry using STA-LIATEST FM (Diagnostica Stago, France). Patients were classified according to the DIC score as non-DIC, non-overt DIC, or overt DIC. ROC curve analyses were performed. RESULTS: The reference limit in the control individuals was determined to be 7.80 µg/mL. Patients with DIC-associated diseases were categorized as non-DIC (N=43), non-overt DIC (N=80), and overt DIC (N=16). ROC curve analyses showed that the diagnostic performance of FM was comparable to DD in both non-overt DIC and overt DIC (P=0.596 and 0.553, respectively). In addition, FM had higher sensitivity, specificity, positive predictive value, and negative predictive value than DD for differentiating overt DIC from non-DIC. CONCLUSIONS: This study demonstrated that the diagnostic performance of FM for DIC was comparable to DD. FM might be more sensitive and more specific than DD in the diagnosis of overt DIC, but not non-overt DIC.

Comparison of high specificity with standard versions of a quantitative latex D-dimer test in the assessment of community pulmonary embolism: HaemosIL D-dimer HS and pulmonary embolism.

BACKGROUND: D-dimer assays are sensitive but have poor specificity. False positive results lead to extra imaging and hospital admissions. OBJECTIVES: To make a pilot comparison of the diagnostic accuracy of the standard quantitative latex HemosIL D-dimer assay with a newer HemosIL D-dimer HS version designed to have improved specificity. PATIENTS / METHODS: Consecutive patients presenting from the community to an Emergency Department that were investigated for suspected pulmonary embolism using a D-dimer test were included in the study. Standard and D-dimer HS tests were performed. Pulmonary Embolism was diagnosed on the basis of imaging studies or post-mortem at any time from presentation to 90 days thereafter. RESULTS: The prevalence of Pulmonary Embolism was 4.5% (18/402). The sensitivity, specificity, negative predictive value, and positive predictive value for the standard quantitative D-dimer test was 100% (81.5 - 100.0), 49.2% (44.1 - 54.3),100% (98.1 - 100.0), and 8.5% (5.1 - 13.0), respectively, and 100% (81.5 - 100.0), 58.3% (53.2 - 63.3),100% (98.4 - 100.0), and 10.1% (6.1 - 15.5), for the D-dimer HS test. There were 35 (16%) fewer 'false positives' using the D-dimer HS assay compared with the standard assay. CONCLUSIONS: D-dimer HS has superior specificity to the standard quantitative D-dimer test without any loss of sensitivity. The generation of fewer false positive results should lead to less unnecessary diagnostic imaging; the use of which is associated with increased hospital admissions and length of stay. The HS assay may therefore have significant health economic benefits.

Human-derived D-dimer for external quality assessment: results of four surveys in Ontario.

External quality assessment (EQA) of D-dimer assays has been limited by a lack of standardized human-derived testing material. In 2006 and 2007, the Quality Management Program--Laboratory Services, Toronto, Canada, investigated the use of commercially prepared lyophilized human plasma spiked with human-derived D-dimer components manufactured by Affinity Biologicals, Hamilton, Canada. Four surveys were performed. Participants reported the level or presence of D-dimer using quantitative or qualitative methods. Participants performing quantitative testing provided their unit of measure and reference interval. Results were considered correct if they fell within the range appropriate for each sample (normal/negative or abnormal/positive). Overall, survey results were excellent, with 4.0% (95% confidence interval [CI], 1.3%-9.1%), 0.8% (CI, 0.0%-1.5%), 2.3% (CI, 0.5%-6.6%), and 2.3% (CI, 0.4%-6.6%) of participants reporting an incorrect result in the first, second, third, and fourth surveys, respectively. A commercially prepared D-dimer is a suitable material for EQA testing.

Diagnostic value of D-dimer in outpatients with suspected deep venous thrombosis receiving oral anticoagulation.

D-dimer has proved a useful diagnostic tool for the exclusion of deep venous thrombosis (DVT). The objective of this paper was to evaluate the diagnostic performance of a diagnostic algorithm combining clinical probability and D-dimer in outpatients receiving oral anticoagulant treatment (OAT) similar to those regularly applied to nonanticoagulated individuals. We enrolled 70 outpatients on OAT who presented with clinically suspected DVT; a standard diagnostic algorithm including clinical evaluation using the modified Wells score and a quantitative immunoturbidimetric D-dimer assay (STA Liatest D-Di; Diagnostica Stago, Asniéres sur Seine, France) was used. A 3-month follow-up period was applied for those patients in whom DVT was initially excluded. The prevalence of DVT was 18.5% (13/70); four of the diagnoses were made during the 3-month follow-up period. The sensitivity, specificity and negative predictive value of D-dimer were 69.2% (95 confidence interval, 42.4-87.3), 47.4% (95% confidence interval, 35.0-60.1) and 87.1% (95% confidence interval, 71.1-94.9), respectively. In conclusion, D-dimer is of limited value in outpatients on OAT presenting with clinically suspected DVT and should be omitted in such individuals; these patients should always undergo compression venous ultrasound, and repeat ultrasonography within 1 week might be warranted in cases with an initial negative examination.

Developmental haemostasis. Impact for clinical haemostasis laboratories.

Developmental haemostasis is a concept, now universally accepted, introduced by Andrew et al. in the late 1980's. However, coagulation analysers and reagents have changed significantly over the past 15 years. Coagulation testing is known to be sensitive to changes in individual reagents and analysers. We hypothesised that the reference ranges developed by Andrew et al. may not be appropriate for use in a modern coagulation laboratory. Our study was designed to determine whether a current day coagulation testing system (STA Compact analyser and Diagnostica Stago reagent system) was sensitive to age-related changes in coagulation assays. This is the first large scale study since Andrew et al. to determine the age associated numerical changes in coagulation proteins. Our results confirm the concepts of developmental haemostasis elucidated by Andrew et al. However, our results clearly demonstrate that the absolute values of reference ranges for coagulation assays in neonates and children vary with analyser and reagent systems. The results confirm the need for coagulation laboratories to develop age-related reference ranges specific to their own testing systems. Without this, accurate diagnosis and management of neonates and children with suspected bleeding or clotting disorders is not possible. Finally we present age related reference ranges for D-dimers, TFPI, and endogenous thrombin potential, previously not described.

The performance of quantitative D-dimer assays in laboratory routine.

Assessment of D-dimer in plasma is routinely used for the exclusion of venous thrombosis and the monitoring of hypercoagulability. Little information is available about the performance of D-dimer assays in clinical laboratories examined by external quality assessment schemes. We obtained results from 423 laboratories measuring plasma pools from patients with elevated D-dimer levels mixed with human normal plasma. The results from five samples were reported containing D-dimer from the lower normal range up to a 20-fold increased level. In addition, information about the assignment of a cut-off point and the medical need to apply these assays was obtained by standardized questionnaire. Participants reported results and additional information from 20 different assays. Lack of standardization regarding the calibration concepts obstructs comparability of results. Results in one sample varied up to 20-fold between the assays applied. In addition, a high variability was reported around the cut-off values introduced for the exclusion of venous thrombosis and pulmonary embolism. As a consequence, generally accepted cut-off values cannot be established. For cut-off assignment, 62% of participants used the kit insert but also 14% used local validation. In conclusion, standardization or at least harmonization of D-dimer assays is necessary to ensure comparability of D-dimer plasma levels measured in clinical routine.

D-dimer testing for deep venous thrombosis: a metaanalysis.

BACKGROUND: The use of D-dimer assays as a rule-out test for deep venous thrombosis (DVT) is controversial. To clarify this issue we performed a systematic review of the relevant literature. METHODS: We identified eligible studies, using MEDLINE entries from February 1995 through October 2003, supplemented by a review of bibliographies of relevant articles. Studies reporting accuracy evaluations comparing D-dimer test results with lower extremity ultrasound or venography in symptomatic patients with suspected acute DVT were selected for review. Two reviewers critically appraised each study independently according to previously established methodologic standards for diagnostic test research. Those studies judged to be of highest quality were designated Level 1. RESULTS: The 23 Level 1 studies reported data on 21 different D-dimer assays. There was wide variation in assay sensitivity, specificity, and negative predictive values, and major differences in methodology of reviewed studies. A multivariate analysis of assay performance, controlling for sample size, DVT prevalence, reference standard, and patient mix, found few differences among the assays in effect on test performance as measured by diagnostic odds ratio. Increasing prevalence of DVT was associated with poorer test performance (P = 0.01), whereas the choice of venography as the reference standard was associated with better test performance (P <0.005). CONCLUSIONS: Explanations for the wide variation in assay performance include differences in biochemical and technical characteristics of the assays, heterogeneity and small size of patient groups, and bias introduced by choice of reference standards. Assay sensitivity and negative predictive value were frequently <90%, uncharacteristic of a good rule-out test. General use of D-dimer assays as a stand-alone test for the diagnosis of DVT is not supported by the literature.

D-dimer: establishing a laboratory assay for ruling out venous thrombosis.

Patients with venous thrombosis (DVT or PE) have elevated D-dimer, a break-down product of cross-linked fibrin. The determination of D-dimer levels is both a diagnostic and a cost savings tool to rule out VTE. The assay can be used to eliminate those individuals without VTE, but with low or moderate clinical suspicion. The D-dimer assay is inexpensive, automated, has a rapid turnaround time, and uses standard blue-top tubes. After appropriate validation, the assay can be 100 percent sensitive in ruling out DVT or PE, but it will not confirm the presence of VTE as numerous other diseases and procedures can increase levels. The assay should not be used routinely on inpatients or surgery patients. Caution should be used when interpreting results from patients on anticoagulation therapy, since lower D-dimer levels may be found. If properly used, the D-dimer assay can save a healthcare facility significant money by eliminating imaging studies on patients with low or moderate suspicion of DVT or PE.