D-Dimer and TAT Measurement in Patients with Deep Venous Thrombosis: Utility in Diagnosis and Judgement of Anticoagulant Treatment Effectiveness

COVID-19-Related Factors Associated with Sleep Disturbance and Suicidal Thoughts among the Taiwanese Public: A Facebook Survey

Coronavirus disease 2019 (COVID-19) pandemic has impacted many aspects of people's lives all over the world. This Facebook survey study aimed to investigate the COVID-19-related factors that were associated with sleep disturbance and suicidal thoughts among members of the public during the COVID-19 pandemic in Taiwan. The online survey recruited 1970 participants through a Facebook advertisement. Their self-reported experience of sleep disturbance and suicidal thoughts in the previous week were collected along with a number of COVID-19-related factors, including level of worry, change in social interaction and daily lives, any academic/occupational interference, levels of social and specific support, and self-reported physical health. In total, 55.8% of the participants reported sleep disturbance, and 10.8% reported having suicidal thoughts in the previous week. Multiple COVID-19-related factors were associated with sleep disturbance and suicidal thoughts in the COVID-19 pandemic. Increased worry about COVID-19, more severe impact of COVID-19 on social interaction, lower perceived social support, more severe academic/occupational interference due to COVID-19, lower COVID-19-specified support, and poorer self-reported physical health were significantly associated with sleep disturbance. Less handwashing, lower perceived social support, lower COVID-19-specified support, poorer self-reported physical health, and younger age were significantly associated with suicidal thoughts. Further investigation is needed to understand the changes in mental health among the public since the mitigation of the COVID-19 pandemic.

Organ-on-Chip Recapitulates Thrombosis Induced by an anti-CD154 Monoclonal Antibody: Translational Potential of Advanced Microengineered Systems

Clinical development of Hu5c8, a monoclonal antibody against CD40L intended for treatment of autoimmune disorders, was terminated due to unexpected thrombotic complications. These life-threatening side effects were not discovered during preclinical testing due to the lack of predictive models. In the present study, we describe the development of a microengineered system lined by human endothelium perfused with human whole blood, a "Vessel-Chip." The Vessel-Chip allowed us to evaluate key parameters in thrombosis, such as endothelial activation, platelet adhesion, platelet aggregation, fibrin clot formation, and thrombin anti-thrombin complexes in the Chip-effluent in response to Hu5c8 in the presence of soluble CD40L. Importantly, the observed prothrombotic effects were not observed with Hu5c8-IgG2σ designed with an Fc domain that does not bind the FcγRIIa receptor, suggesting that this approach may have a low potential risk for thrombosis. Our results demonstrate the translational potential of Organs-on-Chips, as advanced microengineered systems to better predict human response.

Thrombin Generation Biomarkers Decline With Parenteral Anticoagulation-An Overlooked Means of Anticoagulation Monitoring?

Anticoagulation therapy is administered to patients to prevent or stop thrombin generation in vivo. Although plasma tests of in vivo thrombin generation have been available for more than 2 decades, they are not routinely used in clinical trials or practice to monitor anticoagulation therapy. We observed a fall in one such marker, the D-dimer antigen, in patients receiving anticoagulation therapy. We therefore conducted a systematic review of the medical literature to document the change in serum biomarkers of thrombin generation following the initiation of anticoagulation therapy. Using a defined search strategy, we screened PubMed and Embase citations and identified full-length articles published in English. Eighteen articles containing serial changes in 1 of 3 markers of thrombin generation (D-dimer antigen, thrombin–antithrombin complexes, and prothrombin fragment 1+2 antigen levels) in the 14 days following the initiation of anticoagulation were identified. Even though the assays used varied considerably, each of the 3 markers of thrombin generation declined in the initial period of anticoagulation therapy, with changes evident as early as 1 day after beginning therapy. These observations provide a rationale for further exploration of these markers as measures of the adequacy of anticoagulation using classic as well as novel anticoagulants. Particular patient groups that would benefit from additional means of monitoring anticoagulation therapy are discussed.

Thrombin-antithrombin III complex tests

PURPOSE

Patients with fractures of the pelvis and/or lower extremities are at a high risk of developing postoperative venous thromboembolism (VTE). The purpose of this study was to determine whether the thrombin-antithrombin III complex (TAT) tests could be used for postoperative screening of VTE in patients with lower limb or pelvic fractures.

METHODS

We enrolled 133 patients who underwent surgical treatment for fracture of the pelvis or lower extremities. TAT and D-dimer levels were compared in patients with and without VTE. Receiver operating characteristic (ROC) curve analysis was done and the appropriate TAT and D-dimer cutoff levels were determined for VTE screening.

RESULTS

VTE was diagnosed in 41 patients (30.8%). Patients with VTE had significantly higher levels of TAT and D-dimer on postoperative days 1, 3, and 7 than those without VTE, respectively. ROC curve analysis suggested that TAT test at postoperative day 7 had the highest accuracy for predicting postoperative VTE. With the optimal cutoff TAT level of 3.0 ng/mL, sensitivity and specificity were 93.3% and 70.1%, respectively. With the optimal cutoff D-dimer level of 7.4 µg/mL, sensitivity and specificity were 93.3% and 57.0%, respectively.

CONCLUSION

TAT levels measured at postoperative day 7 could be the most useful parameter for screening postoperative VTE. TAT can be used as a screening tool for screening postoperative VTE in patients with lower limb and pelvic fractures.

State-of-the-Art Review: Usefulness of Laboratory Techniques for Evaluating Antithrombotic Efficacy of New Therapeutic Strategies

New drugs and new therapeutic strategies are being introduced for the prevention and the management of cardiovascular and thromboembolic disorders. Extensive clinical studies and large-scale epidemiological investigations are conducted to demonstrate the efficacy of these therapeutic approaches. Laboratory assays are invaluable tools for this exploration. We discuss how the new understanding concerning the regulation of the coagulolytic equilibrium offers novel investigation tools. Parameters reflecting the activities of new drugs targeted to their impact site and presenting few side effects are available. In addition to global clotting methods and chromogenic substrate-based assays, introduction of immunoassays has allowed measurement of most of the molecular markers of hemostatic activation. We recommend use of a panel of markers exploring the endothelial damage, the blood cell involvement, the early coagulant pathways' activation (XIIa and VIIa), the thrombin-formation pathways, the fibrin formation, and the evaluation of the global fibrinolytic capacity. When related to the clinical end points, all these laboratory assays offer useful and reliable monitoring of new drugs. They contribute to the establishment of new therapeutic strategies. Key Words: Hemostasis—Activation—Antithrombotic—Therapy— Laboratory monitoring.

Plasma d-Dimer as a Useful Marker Predicts Severity of Atherosclerotic Lesion and Short-Term Outcome in Patients With Coronary Artery Disease

Increased d-dimer is indicative of a hypercoagulable state and found to be associated with acute coronary syndromes. The present study aimed to evaluate whether plasma d-dimer levels could predict subsequent major clinical events in patients with coronary artery disease (CAD). First, 2209 angiographic-proven patients with CAD were consecutively enrolled. Then, all patients were subjected to follow up for an average of 18 months (ranged from 14 to 1037 days). The relationships of the plasma d-dimer with the severity of CAD and future clinical outcomes were evaluated. We found that plasma d-dimer was higher in patients with prior myocardial infarction (MI) than that in patients with nonprior MI (P = .006). Multivariate linear regression analysis suggested that the plasma d-dimer was linked to the severity of CAD assessed by Gensini score (β = 0.052, 95% confidence interval [CI]: 1.20-6.84, P = .005) even after adjusting for confounding factors. During the follow-up, 42 patients underwent prespecified outcomes. After adjustment for multiple variables in the Cox regression model, the d-dimer levels remained to be a potential predictor of total outcome (hazard ratio = 1.22, 95% CI: 1.09-1.37, P = .001). Therefore, plasma d-dimer levels appeared to be a useful predictor for the severity of CAD and the subsequent major clinical events.

A novel approach for detecting hypercoagulability utilizing thromboelastography

INTRODUCTION

The thromboelastograph is a point-of-care, global hemostasis assay that measures the dynamics of clot formation, including physical properties, over time and is licensed for use in monitoring coagulation during complex surgical procedures. It has more recently been used as a research tool to investigate various bleeding and clotting disorders. Although attempts have been made to use thromboelastography to detect hypercoagulable states, thus far a consistent, reliable approach has not been discovered. The objective of this study was to develop a novel approach utilizing thromboelastography that is sensitive for detecting hypercoagulability.

MATERIALS AND METHODS

Healthy, adult volunteers provided blood samples that were subjected to pre-analytic modifications from standard thromboelastography methods with the goal of prolonging clot initiation and propagation times. The methods which resulted in the desired changes in a consistent and reliable manner utilized corn trypsin inhibitor, a contact pathway inhibitor, on unactivated blood samples. To demonstrate that these methods are sensitive to detecting hypercoagulability, increasing concentrations of recombinant human thrombin were added as a surrogate for hypercoagulability.

RESULTS

Our methods were able to consistently and statistically significantly change the baseline TEG parameters of R time, K time, and angle in the desired fashion. Additionally, these methods were able to detect increasing concentrations of thrombin.

CONCLUSIONS

We describe a novel approach in which thromboelastography is highly sensitive to detecting increasing concentrations of thrombin in vitro. Further studies are underway to determine if these methods will be sensitive for detecting hypercoagulable states in vivo.

Myeloid cell tissue factor does not contribute to venous thrombogenesis in an electrolytic injury model

INTRODUCTION

Tissue factor (TF) is a potent initiator of the extrinsic coagulation cascade. The role and source of TF in venous thrombotic disease is not clearly defined. Our study objective was to identify the contribution of myeloid cell TF to venous thrombogenesis in mice.

MATERIALS AND METHODS

The mouse electrolytic inferior vena cava model was used to induce thrombosis. The following groups of mice were used (1) TF(flox/flox)LysMCre(+) mice that have reduced TF expression in myeloid cells, (2) TF(flox/flox)LysMCre(-) littermate controls, (3) Wild type mice given a monoclonal anti-mouse TF antibody (1H1) to inhibit TF activity, and (4) Wild type mice given rat IgG. Evaluations at baseline, day 2, and day 6 post thrombosis included thrombus weight, vein wall inflammatory cell migration, vein wall TF mRNA, and plasma D-dimer levels.

RESULTS

Inhibition of TF significantly decreased thrombus weight 2days post venous thrombosis. In contrast, TF(flox/flox)LysMCre(+) had no change in thrombus weight when compared to littermate controls. The absence of myeloid cell TF did not affect infiltration of neutrophils or monocytes into the vein wall. TF mRNA expression in the vein wall decreased at 2days but then returned to baseline levels by 6days post thrombosis. D-dimer levels peaked at 2days post thrombosis in mice with or without myeloid cell TF.

CONCLUSIONS

TF is important in the formation of venous thrombi in the macrovasculature. However, TF expression by myeloid cells does not significantly contribute to venous thrombogenesis in this model.

Fibrin D-Dimer Concentration, Deep Vein Thrombosis Symptom Duration, and Venous Thrombus Volume

Introduction: To determine the relationship between fibrin D-dimer levels, symptom duration, and thrombus volume, consecutive patients with incident deep venous thrombosis (DVT) were evaluated. Methods: In a cross-sectional study design, patient symptom onset was determined by careful patient questioning. Venous thrombosis was confirmed by compression duplex ultrasonography. Thrombus volume was estimated based on patient’s femur length using a forensic anthropology method. Fibrin D-dimer was measured by latex immunoassay. Results: 72 consecutive patients with confirmed leg DVT agreed to participate. The median symptom duration at the time of diagnosis was 10 days. The median D-dimer concentration was 1050 ng/dL. The median thrombus volume was 12.92 cm3. D-Dimer levels correlated with estimated thrombus volume (P < .0006 CI 0.12-0.41; R2adjusted = .15) but not symptom duration, patient’s age, or gender. Conclusions: Despite varying symptom duration prior to diagnosis, fibrin D-dimer remains a sensitive measure of venous thrombosis and correlates with thrombus volume.

The use of D-dimer in specific clinical conditions: a narrative review

The use of D-dimer in combination with a clinical decision rule has been widely investigated in pulmonary embolism and deep venous thrombosis. Although it has been shown to be safe in excluding venous thromboembolism, the clinician is often faced with specific situations in which the use of D-dimer is controversial. We review the best available evidence on these patients. We conclude that it is not safe to use D-dimer testing in patients with symptoms of a venous thromboembolism for over 14 days, patients receiving therapeutic heparin treatment and patients with suspected deep venous thrombosis during oral anticoagulant therapy. In these populations the levels of D-dimer can be lower then expected giving rise to false-negative results. It is safe to use D-dimer testing in combination with a clinical decision rule in patients of all ages, patients presenting with a suspected recurrent venous thromboembolism or inpatients with suspected pulmonary embolism. As patients with recurrent venous thromboembolism, elderly patients and inpatients have higher levels of D-dimer, D-dimer testing has a low specificity and the need for additional radiological testing is increased.

Diagnostic accuracy of the Triage® D-dimer test for exclusion of venous thromboembolism in outpatients

BACKGROUND

We evaluated the diagnostic performance of the Triage D-dimer test, a new fast quantitative point-of-care whole blood D-dimer assay and compared it with the Vidas D-dimer assay.

MATERIALS AND METHODS

The study population comprised 319 outpatients for whom D-dimer testing was requested in order to rule out venous thromboembolism (VTE). Routine testing consisted of a plasma ELISA D-dimer analysis (Vidas). For all included patients, an additional EDTA whole blood D-dimer test (Triage) was performed. Patients were classified by reference imaging or by follow-up of the medical record. Accuracy indices, receiver operating characteristics and the kappa coefficient for agreement were calculated using the cutoff values recommended by the manufacturer.

RESULTS

Prevalence of VTE was 14%. Sensitivity and specificity for VTE were 98% (95%CI: 88-100) and 34% (95%CI: 28-40) for Vidas and 91% (95%CI: 78-97) and 42% (95%CI: 36-48) for Triage, respectively. The differences in sensitivity and specificity between both D-dimer assays were statistically significant (McNemar, p<0.0001). ROC-curve analysis yielded an area under the curve of 0.83 (95%CI: 0.76-0.89) for the Vidas and 0.81 (95%CI: 0.74-0.88) for the Triage (p=0.396). The kappa coefficient for agreement between Vidas and Triage was 0.75 (95%CI: 0.68-0.79).

CONCLUSIONS

The Triage and Vidas D-dimer tests show comparable diagnostic accuracy. Vidas showed a significant higher sensitivity. Our findings strongly suggest lowering the cutoff for the Triage D-dimer test from 400 to 350 ng/mL. In this way specificity lowers from 42 to 38%, but, more importantly, sensitivity increases from 91 to 95%.

Valeur des D-dimères lors des thromboses veineuses superficielles des membres inférieurs

OBJECTIVE

The negative predictive value of D-dimer (DD) assay in patients with venous thromboembolic disease is well established for deep vein thrombosis and pulmonary embolism. Little is known about the value of DD assay in patients with superficial thrombophlebitis (ST). The purpose of this study was to assess the value of DD assay in patients with ST of the lower limb.

METHOD

The study group was composed of 100 consecutive patients, irrespective of age. Patients with clinical manifestations suggestive of ST of the lower limbs with positive duplex color Doppler evidence confirming the diagnosis and DD assay results (Vidas D-Dimer Exclusion) within 24 hours were included in the study. Patients with thrombosis in another site in addition to the superficial vein of the lower limb, those taking anticoagulants for more than 48 hours, and those with a condition known to potentially elevate DD levels were excluded. The volume of the thrombus was determined echographically and reported as mean diameter and length.

RESULTS

Sixty-two women and 38 men were included. Mean age (+/- 5) was 58 years +/- 13.48 (range 18-90; median: 57). The ST involved the Great saphenous (n=74), the small saphenous (n=11) or another vein (n=15). Mean thrombus volume was 4453 mm(3) +/- 7101 (range 94-38484; median: 1751). Mean DD level was 829 ng/ml +/- 516.72 (range 100-2567; median: 715.5). DD assay was negative (<500 ng/ml) in 32 patients (32%) and positive in 68 (68%). For these three items, there was no significant difference between ST with and without varicose veins. DD assay was always positive (>or=500 ng/ml) in all patients aged over 70 years (n=22). In patients aged less than 70 years (n=78), DD assay was positive in 46 (59%) and negative in 32 (41%). DD level was positively correlated with thrombus volume in patients aged less than 70 years (P<0.0001). ROC analysis, sensitivity as a function of specificity by thrombus volume for the entire population, determined the usefulness of a negative DD assay. Considering the critical threshold at 5914 mm(3), sensitivity was 1.0 (95CI 0.89-1.0), with 0.29 specificity (95CI 0.19-0.42), 1.00 negative predictive value and 0.75 positive predictive value. However, the thrombus volume was less than this threshold value in three of the nine cases of ST with extension to the terminal portion of the saphenous.

CONCLUSION

A positive DD assay was observed in 68% of patients with ST, with no significant difference with or without varicose veins. The test was positive in all patients aged over 70 years and in 59% of those aged under 70 years. There was a correlation between DD level and thrombus volume, yielding a threshold volume (5914 m(3)) above which all DD tests were positive. Nevertheless, this threshold volume was too great to include all ST extending to the terminal portion of the saphenous. Measurement of DD level is thus not contributive to the diagnosis of ST.

[D-dimer levels in venous thromboembolism]

Venous thromboembolism (VTE) is associated with substantial morbidity and mortality. The clinical signs and symptoms are unspecific, widely varying from asymptomatic to sudden death. The diagnostic algorithm of VTE is an evolving field, in which D-dimers (DD) determination has been used as one of the preferred screening tests. Clinical management studies are clarifying the role of DD in the diagnostic paradigm of VTE. Published reports support the use of plasma DD determination in patients with a low clinical probability of VTE. Patients with moderate or high clinical probability of VTE show a higher probability of false negative plasma DD values. This fact forces the clinician to use more complex diagnostic test in order to either confirm or exclude VTE. A variety of different qualitative and semi-quantifiable assays are available for plasma DD determination. There is a wide variation in performance and there are discrepancies in the comparability of the different assays. Therefore, in order to both appropriately incorporate plasma DD determination in the diagnostic strategies of VTE and to reduce unnecessary investigations, clinicians should ensure that they are familiar with the diagnostic performance of the assay used in their own institution allowing a safer and cost-effective procedure.

Changes in coagulation-fibrinolysis marker and neutrophil elastase following the use of tourniquet during total knee arthroplasty and the influence of neutrophil elastase on thromboembolism

BACKGROUND

To clarify in detail the mechanism underlying the development and exacerbation of deep venous thrombosis (DVT) and/or pulmonary thromboembolism (PTE), we focused on the following factors: the thrombin-antithrombin III complex (TAT), D-dimer and neutrophil elastase (NE). We basically investigated whether NE played an important role in the development of PTE I a mice model.

METHODS

Nineteen rheumatoid arthritis (RA) and six osteoarthritis (OA) patients underwent total knee arthroplasty (TKA) with tourniquet, and 13 RA and 12 OA patients underwent TKA without tourniquet in each group. The blood levels of TAT, D-dimer and NE were measured before surgery, immediately after and during the days following surgery. For the induction of experimental PTE due to coagulation of platelets, adenosine diphosphate (ADP) was administrated, and human NE with ADP was also administrated for the development of DVT and/or PTE.

RESULTS

The rates of increase in the mean TAT, D-dimer and NE levels in the group with tourniquet were statistically higher than those in the group without tourniquet after surgery. The mortality of the mouse due to PTE increased from 43 to 67% following ADP and human NE administration compared to a single ADP administration. Histological changes of the lungs in the mice receiving NE and ADP injections were characterized by a diffuse and extensive accumulation of platelets and fibrin in alveolar capillaries and other microvessels.

CONCLUSION

We suggest that during TKA, the use of tourniquet induces local release of a large amount of NE from neutrophils, inducing the development of DVT and/or PTE and their exacerbation.

Can causes of false-normal D-dimer test [SimpliRED] results be identified?

BACKGROUND

To simplify the diagnostic strategy of patients suspected for venous thromboembolism, the use of D-dimer tests has been advocated. Very important for the safety of such diagnostic strategies would be the capacity to recognise false-normal D-dimer results, in order to prevent inadequately withholding anticoagulant treatment in patients who actually have the disease. Insight in the causes of false-normal D-dimer results would therefore be necessary. We hypothesised that certain patient characteristics are associated with relatively low plasma D-dimer levels and, therefore, could increase the risk of false-normal results.

METHODS

Consecutive patients with an objectively confirmed venous thromboembolic event and an independently obtained false-normal SimpliRED D-dimer test result were included in the study. For each patient, two controls with objectively confirmed venous thromboembolism and an adequate abnormal D-dimer result were selected. Baseline patient characteristics, obtained by standardised questionnaires, were compared between the two groups of patients.

RESULTS

In total, 686 patients had a venous thromboembolic event and 47 of these patients had a false-normal SimpliRED result. Therefore, the overall sensitivity of the SimpliRED test for venous thromboembolism was 94% (95% CI: 92-95%). Although the prevalence of certain clinical characteristics was significantly higher in patients with a false-normal D-dimer result than in the controls [odds ratios for (LMW)heparin treatment and symptoms lasting more than 10 days: 5.1 (95% CI: 1.5-18.7) and 3.2 (95% CI:1.4-7.4), respectively], the prevalence of these characteristics was also high in the control group with an adequate abnormal D-dimer. Combining two or more of these characteristics had a low prevalence and did not further improve the ability to identify those patients with a false-normal D-dimer test at presentation.

CONCLUSIONS

Although these findings clearly indicate an association between certain baseline clinical characteristics and the occurrence of a false-normal SimpliRED test, the clinical utility for these characteristics is limited.

Low molecular weight heparin (dalteparin) is equally effective as unfractionated heparin in reducing coagulation activity and perfusion abnormalities during the early treatment of pulmonary embolism

Little is known about the differences between unfractionated heparin (UFH) and low molecular weight heparin (LMWH) with regard to their effects on coagulation activity during treatment for pulmonary embolism. The objective of this study was to compare UFH and LMWH (dalteparin) in the early treatment of pulmonary embolism in terms of control of coagulation markers and perfusion abnormalities. Thirty-seven patients with acute pulmonary embolism were randomized to receive intravenous UFH or subcutaneous dalteparin, each accompanied by acenocoumarol. Daily blood samples were obtained for the measurement of thrombin generation (fragments 1 and 2 [F1+2], thrombin-antithrombin (TAT) complexes and fibrin monomers [FMs]) and fibrinolysis (d-dimer concentrations and clot-lysis times). Ventilation-perfusion scintigraphies were performed, and with the data they yielded, percentage of vascular obstruction scores (PVOs) were calculated on days 0 and 5. The international normalized ratio was within the therapeutic range in both groups on day 3. F1+2 and TAT complexes rapidly normalized, without differences between the groups (P =.5 and.4, respectively). FM levels did not decrease and, in fact, showed an increase in the UFH group from day 3 on (P <.05 between groups). d-Dimer levels decreased over time, with no differences between groups (P =.6). Clot-lysis times were shorter in the UFH group (P <.05). PVOs on days 0 and 5 were not different (P =.5 and.8, respectively), but the decrease in PVOs over time was greater in the dalteparin group (P =.04). These results show that dalteparin is at least as effective as UFH in reducing coagulation activity and perfusion abnormalities in the early treatment of pulmonary embolism.

Limitations of D-dimer testing in unselected inpatients with suspected venous thromboembolism

PURPOSE

To determine the utility and limitations of D-dimer testing for the evaluation of venous thromboembolism in hospitalized patients.

METHODS

We performed D-dimer testing by four different methods in unselected inpatients undergoing radiologic evaluation for possible venous thromboembolism. We included patients with a history of malignancy, recent surgery, thrombosis, and anticoagulation treatment. C-reactive protein levels were assayed as a measure of inflammation.

RESULTS

Of 45 patients with radiographically proven proximal deep venous thrombosis or pulmonary embolism, 43 had elevated D-dimer levels by enzyme-linked immunosorbent assay (ELISA) (sensitivity, 96%); the specificity of the test was 23% (36/157). The qualitative non-ELISA tests had higher specificities, but their sensitivities were <70%. Nineteen patients (42%) with thrombosis had false-negative D-dimer tests by at least one assay. The specificity of the tests decreased with increasing duration of hospitalization, increasing age, and increasing C-reactive protein levels. D-dimer testing had little or no utility in distinguishing patients with thrombosis from those without in patients who had been hospitalized for more than 3 days, were older than 60 years, or had C-reactive protein levels in the highest quartile.

CONCLUSION

In unselected inpatients, D-dimer testing has limited clinical utility because of its poor specificity. This is particularly true for older patients, those who have undergone prolonged hospitalization, and those with markedly elevated C-reactive protein levels. In some patient subsets, a negative non-ELISA D-dimer test cannot discriminate between inpatients with and without thrombosis.

Thrombus precursor protein, endogenous thrombin potential, von-Willebrand factor and activated factor VII in suspected deep vein thrombosis: is there a place for new parameters?

Because of its high negative predictive value, D-Dimer is an important parameter in the exclusion of deep vein thrombosis (DVT) but it produces a high number of false-positive results. We therefore evaluated different blood parameters in 74 consecutive patients with suspected DVT, whose final diagnosis was based on the results of Duplex ultrasound or venography. DVT was diagnosed in 52.7%. While D-Dimer, thrombin-antithrombin complexes, prothrombin fragment 1+2, von-Willebrand factor and thrombus precursor protein were significantly increased in patients with DVT, there was no influence concerning endogenous thrombin potential and activated factor VII. There was no significant correlation between the thrombus extension or the duration of symptoms with any of these parameters. D-Dimer showed the best sensitivity (94.9%) to specificity (45.7%) ratio and neither the sole nor the additional evaluation of any other investigated parameter increased its diagnostic performance. We, therefore, conclude that the determination of D-Dimer remains the 'gold standard' in the laboratory testing of patients with suspected DVT.

Usefulness of a semiquantitative D-dimer test for the exclusion of deep venous thrombosis in outpatients

PURPOSE

The D-dimer test is used commonly in diagnostic strategies to reduce the need for ultrasonography in patients suspected of having deep venous thrombosis. We studied several clinical and laboratory variables that might limit the accuracy of a semiquantitative D-dimer test.

SUBJECTS AND METHODS

In this retrospective cohort study, 704 outpatients suspected of having deep venous thrombosis underwent a semiquantitative D-dimer test and ultrasonography. The performance of the D-dimer test was calculated in patients using anticoagulants (n =61), patients with previous thrombosis (n =127), and patients with malignancy (n =47), including 39 patients with more than one of these characteristics. The 508 remaining patients were considered to be the reference group.

RESULTS

A total of 254 patients (36%) had evidence of deep venous thrombosis. The D-dimer test had a sensitivity of 99% (174/176; 95% confidence interval [CI]: 96% to 100%) and a negative predictive value of 98% (98/100; 95% CI: 93% to 100%) in the reference group. The sensitivity of the D-dimer test in patients using oral anticoagulants was 75% (6/8; 95% CI: 35% to 97%; P =0.01 compared with the reference group). Test sensitivity was 96% (51/53; 95% CI: 87% to 100%) in patients with previous thrombosis, and 100% (29/29; 95% CI: 88% to 100%) in patients with cancer. However, 553 (79%) of all patients, including 43 of the cancer patients (91%), had an abnormal D-dimer test.

CONCLUSION

The semiquantitative D-dimer test in this study has a high sensitivity and negative predictive value in the exclusion of deep venous thrombosis, except perhaps among patients using oral anticoagulants. D-dimer tests in patients with cancer and in patients over 70 years old may not be worthwhile, because the tests are usually positive.

Decrease in sensitivity of D-dimer for acute venous thromboembolism after starting anticoagulant therapy

D-dimer testing is useful for the exclusion of acute venous thromboembolism (VTE). Anticoagulant therapy is expected to reduce D-dimer levels in patients with thrombosis and, consequently, it may not be safe to use D-dimer levels to exclude VTE after anticoagulant therapy has been started. The objectives of this study were to estimate the decrease in D-dimer levels after 24 h of heparin therapy and, applying this estimate to the results of a recent study, to calculate the expected reduction in sensitivity. Using pre-defined criteria, we first performed a literature review to determine whether, and by how much, D-dimer levels decrease within 24 h of starting heparin therapy in patients with acute VTE. Using D-dimer levels that were measured in a prospective study of patients with confirmed deep vein thrombosis and/or pulmonary embolism as baselines, we then determined the change in sensitivity (and specificity) that would result from the fall in D-dimer levels that the literature review suggested would have occurred after 24 h of heparin therapy. On the basis of the literature review, we calculated that mean D-dimer levels decrease by 25%, 24 h after starting heparin therapy in patients with acute VTE. This 25% decrease in D-dimer levels resulted in a decrease in sensitivity from 95.6% (95% confidence interval, 90.0-98.6) to 89.4% (95% confidence interval, 83.7-95.1). There is a decrease in D-dimer levels in patients with acute VTE 24 h after starting heparin therapy that is expected to result in a clinically important drop in sensitivity.

Noninvasive diagnosis of incomplete endovascular aneurysm repair: D-dimer assay to detect type I endoleaks and nonshrinking aneurysms

PURPOSE

To test the hypothesis that D-dimer (D-D), a cross-linked fibrin degradation product of an ongoing thrombotic event, could be a marker for incomplete aneurysm exclusion after endovascular abdominal aortic aneurysm (AAA) repair.

METHODS

In a multicenter study, 83 venous blood samples were collected from 74 AAA endograft patients and controls. Twenty subjects who were >6 months postimplantation and had evidence of an endoleak and/or an unmodified or increasing AAA sac diameter formed the test group. Controls were 10 nondiseased subjects >65 years old, 18 AAA surgical candidates, and 26 postoperative endograft patients with no endoleak and a shrinking aneurysm. Blood samples were analyzed for D-D through a latex turbidimetric immunoassay. The endograft patients were stratified into 5 clinical groups for analysis: no endoleak and decreasing sac diameter, no endoleak and increasing/unchanged sac diameter, type II endoleak and decreasing sac diameter, type II endoleak and increasing/unchanged sac diameter, and type I endoleak.

RESULTS

Individual D-D values were highly variable, but differences among clinical groups were statistically significant (p < 0.0001). D-D values did not vary significantly between patients with stable, untreated AAAs and age-matched controls (238 +/- 180 ng/mL versus 421 +/- 400 ng/mL, p > 0.05). Median D-D values increased at 4 days postoperatively (963 ng/mL versus 382 ng/mL, p > 0.05) and did not vary thereafter if there was no endoleak and the aneurysm sac decreased. D-D mean values were higher in patients with type I endoleak (1931 +/- 924 ng/mL, p < 0.005) and those with unchanged/increasing sac diameters (1272 +/- 728 ng/mL) than in cases with decreasing diameters (median 638 +/- 238 ng/mL) despite the presence of endoleak (p < 0.0005).

CONCLUSIONS

Elevated D-D may prove to be a useful marker for fixation problems after endovascular AAA repair and may help rule out type I endoleak, thus excluding patients from unnecessary invasive tests.

Markers of plasma coagulation and fibrinolysis after acute deep venous thrombosis

OBJECTIVE

Plasma markers of coagulation and fibrinolysis have proved sensitive in the initial diagnosis of acute deep venous thrombosis (DVT). The purpose of this study was to examine the evolution and utility of measuring D-dimer and prothrombin fragment 1+2 (F 1+2) levels after an acute DVT.

METHODS

Subjects with DVT confirmed by ultrasonography had quantitative plasma D-dimer and F 1+2 levels determined before anticoagulation. Ultrasound scan and coagulation studies were repeated at 3, 7, and 14 days; 1 month; and every 3 months for 1 year.

RESULTS

Sixty-one patients with a median initial thrombus score of 3 (interquartile range, 2-7) were followed up for 266 days (interquartile range, 91.5-364 days). Initial D-dimer levels were elevated in 92.7% of patients and were associated with thrombus extent (P =.003), whereas F 1+2 levels were increased in 94.5% of patients and were lower in patients with isolated calf vein thrombosis (P =.001). Initial D-dimer (P =.002) and F 1+2 levels (P =.009) were significantly higher in the 26 (43%) patients with recurrent thrombosis during follow-up. Initial D-dimer levels of 2000 ng/mL or greater were predictive of recurrent events after both proximal and isolated calf vein thrombosis. Although interval increases in these markers had little value in detecting recurrent thrombotic events, D-dimer levels of 1000 ng/mL or greater and 500 ng/mL or greater had respective sensitivities of 89.3% and 100% in detecting early and late recurrences. Corresponding specificities were 35.6% and 53.9%.

CONCLUSIONS

Initial D-dimer levels are determined by total thrombus load and remain elevated long after an acute DVT. F 1+2 levels are less sensitive to thrombus score and return to baseline more quickly. Initial levels of these markers may have some utility in predicting the risk of ultrasound scan-documented recurrences, whereas increased D-dimer levels are a sensitive but nonspecific marker of these events.

The use of thrombus precursor protein, D-dimer, prothrombin fragment 1.2, and thrombin antithrombin in the exclusion of proximal deep vein thrombosis and pulmonary embolism

We examined various nonSTAT commercially available coagulation activation markers in an attempt to help diagnose or exclude the often subtle clinical presentations of proximal deep vein thrombosis (PDVT) and pulmonary embolism (PE). Fifty-five patients presenting to the Emergency Department were completely assessed. Eleven patients were diagnosed with PDVT, six patients were diagnosed with PE, and three patients were diagnosed with both PDVT and PE. Thrombus precursor protein (TpP) excluded the diagnosis in 19 of the 35 patients negative for PDVT and/or PE, D-Dimer in 15 patients, prothrombin fragment 1.2 in 17 patients, and thrombin-antithrombin (TAT) in 14 patients. Both the TpP and TAT enzyme-linked immunosorbent assay (ELISA) tests had 100% sensitivity and negative predictive value for evaluating PDVT and/or PE. The TpP ELISA had the highest specificity (54%) of all four markers studied.

Value of thrombin-antithrombin III complexes in major orthopedic surgery: relation to the onset of venous thromboembolism

This study evaluated (a) the possible changes of plasma levels of thrombin-antithrombin III complexes during hospitalization to predict venous thromboembolism in patients undergoing elective total hip replacement and (b) the sensitivity and specificity of thrombin-antithrombin III complexes in the late incidence of deep vein thrombosis when these patients are discharged from the hospital. In 50 consecutive patients (18 men, mean age = 63 +/- 8 years) a venous blood sample was obtained from each patient before surgery and postsurgery on days 5 +/- 2, 9 +/- 2, and 45 to evaluate the thrombin-antithrombin III complexes by the enzyme-linked immunosorbent assay as a part of a larger surveillance program. Six of 50 patients developed deep vein thrombosis, diagnosed by phlebography on the 45th day postsurgery. From the day before until the ninth day after surgery, mean values of the thrombin-antithrombin III complexes increased to a greater extent in patients with deep vein thrombosis than in those without, although the differences were not significant (from 14.8 +/- 11.2 ng/mL to 36.2 +/- 19.1 ng/mL in the former group and from 13.6 +/- 3.3 ng/mL to 22.4 +/- 5.1 ng/mL in the latter, p = NS). On the 45th day after surgery the mean value of the thrombin-antithrombin III complexes reduced less in patients with deep vein thrombosis (up to 9.9 +/- 1.9 ng/mL and to 25.2 +/- 17.2 ng/mL, respectively, p = NS). In addition, thrombin-antithrombin III complexes remained over the level reached on the fifth day only in the patients who developed deep vein thrombosis. On the 45th day after surgery, thrombin-antithrombin III complexes exhibited a sensitivity of 17%, a specificity of 86%, and an accuracy of 78% in differentiating the presence and absence of deep vein thrombosis as compared with phlebography. We conclude that after total hip replacement (a) serial measurement of the thrombin-antithrombin III complexes does not appear helpful in predicting venous thromboembolism during hospitalization, and (b) measurement of thrombin-antithrombin III complexes has a low diagnostic accuracy in diagnosing delayed deep vein thrombosis. However, the greater and persistent increase of thrombin-antithrombin III complexes level in patients who developed deep vein thrombosis may deserve further investigations.

Rapid fibrin D-dimer tests for deep venous thrombosis: factors affecting diagnostic utility

Measurement of fibrin D-dimer may be a useful diagnostic test to exclude a diagnosis of deep venous thrombosis (DVT) in the emergency department setting. However, the specific assay format may influence its sensitivity and ultimate clinical utility. We tested samples from 200 patients under evaluation for DVT using three fibrin D-dimer assays: the SimpliRED whole blood agglutination assay, a latex agglutination assay, and the Dimertest EIA. Latex agglutination assays were performed in both a specialized laboratory and a routine laboratory. The negative predictive value for all tests was > 90%. The sensitivity of the SimpliRED assay was similar to that of the latex assay. The sensitivity of the latex assay was significantly lower when performed by generalist laboratory technologists. Thus, while D-dimer may be a useful test for the exclusion of DVT, subjective endpoint latex agglutination assays should be performed only by appropriately trained personnel.

Determinants of plasma fibrin D-dimer sensitivity for acute pulmonary embolism as defined by pulmonary angiography

BACKGROUND

The reported operating characteristics of the plasma fibrin D-dimer level for the diagnosis of acute pulmonary embolism vary widely.

OBJECTIVE

To determine the sensitivity, specificity, predictive value, and clinical utility of the D-dimer for the diagnosis of pulmonary embolism, and to describe the effect of D-dimer assay method (enzyme-linked immunosorbent assay [ELISA], latex agglutination, membrane ELISA) and discriminate level, patient location at onset, comorbid disease, duration and intensity of concurrent heparin administration, and duration of symptoms on these operating characteristics.

DESIGN

Prospective laboratory investigation.

SETTING

Community and tertiary care teaching hospital.

PATIENTS

Consecutive patients with suspected acute pulmonary embolism referred for pulmonary angiography from April 1993 through March 1996.

MEASUREMENTS

Baseline characteristics, the duration and intensity of heparin anticoagulation, the time interval between symptom onset and plasma D-dimer testing, pulmonary angiography, and the D-dimer level on the day of pulmonary angiography.

RESULTS

Of 105 consenting patients, 33 (31%) had a positive pulmonary angiogram. The D-dimer sensitivity/ negative predictive value for the ELISA, latex agglutination (American Bioproducts Co/Diagnostica Stago and Biopool International), and membrane ELISA were 100%/100%, 94%/94%, 100%/100%, and 97%/96%, respectively, at a discriminate level of 250 microg/L or less. The clinical utility, defined as the prevalence of a negative test, ranged from 17% to 33%. D-dimer sensitivity was unaffected by patient location at onset, comorbid disease, or heparin therapy but was inversely related to the duration of symptoms.

CONCLUSIONS

The sensitivity of the plasma fibrin D-dimer for the diagnosis of pulmonary embolism depends on the assay method, the assay-specific discriminate level, and the duration of symptoms. At the appropriate discriminate level, the plasma D-dimer is a sensitive but nonspecific test for the diagnosis of pulmonary embolism.

Elevated activation markers of coagulation in patients undergoing orthognathic surgery

Surgery is associated with a variable but increased incidence of postoperative venous thromboembolism (VTE). The risk of VTE after orthognathic surgery is unknown. Recently developed assays for activation markers of blood coagulation allow the detection of a prethrombotic state and may thus help to identify surgical procedures with a risk of postoperative VTE. The pre- and postoperative levels of thrombin-antithrombin complex (TAT) and prothrombin fragment 1+2 (F1+2) were studied in ten patients undergoing orthognathic surgery. Mean levels of TAT and F1+2 were within the normal range preoperatively (TAT:2.6+1.0 microg/L, F1+2:0.8+0.2 nmol/L). A significant increase in both parameters occurred postoperatively (TAT:21.8+21.4 microg/L, P<0.005; F1+2:1.3+0.4, P<0.02). No increase was observed in a control group (n=13) consisting of patients undergoing minor surgical procedures in general anesthesia. Our study shows that a marked activation of the coagulation cascade occurs during orthognathic surgery which warrants further studies on the true incidence of postoperative VTE in patients undergoing orthognathic surgery.

Laboratory diagnosis of venous thromboembolism

Venous thromboembolism is a common medical condition in both out-patients and in-patients. Despite the development of non-invasive tests, the diagnosis of deep vein thrombosis and pulmonary embolism remains a clinical challenge. In an effort to improve diagnostic accuracy and to reduce the necessity of serial testing, laboratory markers of thrombin generation and fibrinolysis have been investigated as first-line screening tests. Although the majority of markers are elevated in acute thrombosis, D-dimer, a specific derivative of cross-linked fibrin, appears to have the most potential clinical utility. Accuracy studies and preliminary management trials suggest that rapid D-dimer enzyme-linked immunosorbent assays and the whole blood agglutination assay, SimpliRED D-dimer (Agen Biomedical, Brisbane, Australia), have strong potential as exclusionary tests in patients with suspected venous thrombosis.

Diagnostic management of venous thromboembolism

The accuracy of diagnostic methods for the diagnosis of deep vein thrombosis and pulmonary embolism in symptomatic patients is critically reviewed. In addition, the safety of withholding anticoagulant therapy from patients with suspected deep vein thrombosis or pulmonary embolism in whom the qualified diagnostic strategy was normal is evaluated by determining the frequency of venous thromboembolic complications during 3 months of follow-up. It is shown that the currently used available diagnostic techniques for deep vein thrombosis are all able to identify the majority of patients who indeed have venous thrombosis. However, as result of its accuracy and practical advantages, compression ultrasound is the test of choice in the evaluation of symptomatic patients. Patients with a normal test outcome should be re-tested to detect the small proportion of patients with proximally extending calf vein thrombosis. In the strategy of repeated diagnostic testing, impedance plethysmography could be used as an alternative to ultrasonography. To obtain a reduction in repeat tests various diagnostic strategies have been evaluated and it was shown that these strategies, using non-invasive tests, can be as accurate and safe as the invasive reference strategy. The safeties of the various strategies were very similar; however, important differences were observed with respect to the practical implementation of the various diagnostic strategies. Simplification of the repeated testing strategy by using a D-dimer assay and/or a clinical decision rule seems to be promising. The reference standard for the diagnosis of pulmonary embolism remains pulmonary angiography. Several strategies based on non-invasive diagnostic methods have been evaluated for their safety and complexability. Perfusion-ventilation lung scanning is the most thoroughly evaluated non-invasive technique so far. It seems safe to withhold anticoagulant therapy in patients suspected of pulmonary embolism with a normal perfusion lung scan result; however, further testing is needed in the case of a non-diagnostic perfusion-ventilation lung scan result. At this moment angiography is the method of choice in this category of patients. D-dimer assays, clinical decision rules and ultrasound examinations of the legs seem to have a high potential to limit the need for angiography. Also, spiral computerized tomography and magnetic resonance imaging are promising techniques, but their role in the diagnostic management of pulmonary embolism is still uncertain.

Prethrombotic state due to hypercoagulability in patients with permanent transvenous pacemakers

Venous thrombosis is a relatively usual but serious complication of permanent transvenous pacing. However, the pathogenesis has not been defined. To clarify underlying abnormalities in the coagulation-fibrinolysis system in patients with permanent transvenous pacemakers, we measured serum levels of fibrinopeptide A (FPA), thrombin-antithrombin III complexes (TATs), plasmin-alpha 2 plasmin inhibitor complexes (PICs), D-dimer (D-D), beta-thromboglobulin (beta-TG), and platelet factor 4 (PF4) in 53 patients with permanent transvenous pacemakers and 10 control subjects. The patients were divided into two groups, as follows, according to the presence of mural thrombus documented along the pacing lead(s) by digital subtraction angiography and transesophageal echocardiography: Group Th (-), patients without venous route thrombus; and Group Th (+), patients with venous route thrombus. FPA and TAT levels increased significantly even in Group Th (-), and further increased in Group Th (+) compared with control subjects (FPA: 7.5 +/- 4.9, 15.3 +/- 8.8 vs 3.0 +/- 1.4 ng/mL, respectively, P < 0.05; TAT: 2.9 +/- 1.3, 4.8 +/- 2.3 vs 1.7 +/- 0.6 ng/mL, respectively, P < 0.05). There were no differences in levels of D-D, PIG, beta-TG, and PF4 among control subjects, Group Th (-), and Group Th (+). These findings suggest that the hypercoagulable state appears in patients with permanent transvenous pacemakers, even without apparent venous thrombosis. The patients with permanent transvenous pacemakers are thought to be in the prethrombotic state even if they have no venous route thrombosis.

Systemic activation of coagulation and fibrinolysis during varicose vein stripping

BACKGROUND

Elevation of activation markers of blood coagulation (thrombin-antithrombin complex [TAT], prothrombin fragment 1 + 2 [F1 + 2], D-Dimer] has not only been found in clinically overt thrombosis but also reflects a prethrombotic state.

OBJECTIVE

The purpose of our study was to evaluate whether varicose vein stripping, an operative procedure with an extremely low risk of postoperative thromboembolism, induces a prethrombotic state by activation of the hemostatic system.

METHODS

In a prospective, observational study we compared the baseline and postoperative values of TAT, F1 + 2, and D-Dimers in 15 patients undergoing varicose vein stripping and in 11 control patients undergoing surgical procedures associated with only minor soft tissue trauma.

RESULTS

A highly significant postoperative elevation of TAT (P < 0.001), F1 + 2 (P = 0.006), and D-Dimer (P < 0.001) was observed in the varicose vein stripping group. No significant postoperative change of the respective parameters was detected in the control group.

CONCLUSION

We therefore conclude that varicose vein stripping induces a significant hemostatic system activation although postoperative thrombotic events are rare.

Effects of long travels in sitting position in elderly volunteers on biological markers of coagulation activation and fibrinolysis

OBJECTIVE

To evaluate whether long travel in sitting position is associated with an increase of coagulation activation and/or a decrease of fibrinolytic activity.

DESIGN

Comparison of blood coagulation and fibrinolysis parameters before and after two pleasure trips by bus organized in winter period (600 km in 8 hours) and in summer period (1200 km in 16 hours).

SUBJECTS

31 and 23 healthy elder volunteers for the winter and the summer trip respectively. Nine other elder volunteers were selected as a control group for the winter study.

MAIN OUTCOME MEASURES

prothrombin fragment 1 + 2 (F1 + 2), thrombin-antithrombin III (TAT), D-dimers (D-D), factor VII activated, plasminogen activator inhibitor (PAI), tissue-type plasminogen activator (t-PA), plasma albumin.

RESULTS

A significant difference before and after the travel was only observed for TAT in the summer period. However all values of TAT were in the normal range. No volunteer presented with thromboembolic disease during the month following the travel.

CONCLUSION

In the condition of our study, long travel in sitting position does not lead to an enhanced procoagulant state for elderly with varicose veins. These results suggest that there is no biological support to propose heparin prophylactic therapy for the elderly with varicose veins wishing to travel by bus.

The value of quantitative fibrin monomer determination in the early diagnosis of postoperative deep vein thrombosis

A new test for the determination of fibrin monomer in plasma was clinically evaluated in comparison to the plasma concentration of D-D, TAT and F1,2 for the early diagnosis of prethrombotic conditions. For this purpose 129 patients who underwent abdominal surgery were followed longitudinally. 12 patients developed DVT postoperatively, proved by phlebography. The identical specificity level 73.2% was chosen for all 4 tests. At this specificity, FM had the highest sensitivity (91.7%), followed by D-D (75.0%), TAT (41.7%) and F1,2 (33.3%). All FM-positive DVT-patients had pathological FM-values at least one day prior to the clinical manifestation of thrombosis. In a group of 255 obviously healthy persons the cut-off value for the new FM test was determined at 3.6 mg/l (95th percentile). No clinically relevant influence of gender, age, smoking habits or oral anticonception could be observed. It is concluded that FM is a valuable diagnostic tool for the early diagnosis of prethrombotic conditions.

Low Risk of Subsequent Deep-Venous Thrombosis in Patients with a Negative Venous Duplex Scan

Venous duplex scanning (VDS) is sensitive and specific for proximal deep-vein thrombosis (DVT) but has poor sensitivity for isolated calf DVT, some of which can extend to the proximal veins and result in clin ically significant pulmonary emboli. The intent of this study was to determine the long-term outcome of outpa tients with negative VDS and to assess the accuracy of three biochemical markers of hypercoagulability for the detection of DVT. Consecutive ambulatory patients re ferred to our vascular laboratory with a question of lower extremity DVT had plasma determination of D-dimer, prothrombin fragment 1.2, and thrombin-antithrombin complex. Additionally, patients with a negative VDS were followed for 6 months to determine the frequency of subsequent venous thrombosis. Of 207 patients seen in our vascular laboratory, 171 had either a single negative VDS or two negative studies (done 24-72 h apart). Fol low-up of 161 patients for 6 months showed no evidence of venous thromboembolism. The remaining 10 patients died from other causes or had alternative diagnoses made to explain their symptoms. The D-dimer and thrombin- antithrombin complex had equal test accuracy for the di agnosis of DVT and were superior to the prothrombin fragment 1.2 levels. Symptomatic venous thromboembo lism occurring after negative VDS is uncommon. D-dimer and thrombin-antithrombin levels have equal utility as diagnostic tests for DVT.

A new sensitive membrane based ELISA technique for instantaneous D.Dimer evaluation in emergency

D.Dimer is currently used as a diagnotic help in thromboembolic events. The first application widely validated concerns the exclusion diagnosis of deep vein thrombosis and pulmonary embolism. In this context D.Dimer measurements must be performed individually and they must offer a good accuracy in evaluating the clinical decision threshold which is of 0.5 micrograms/ml when D.Dimer is expressed as initial fibrinogen equivalent. For this objective we report a new membrane based ELISA technique, which uses an immunofiltration device and two complementary monoclonal antibodies. The first one is coated onto the membrane and is used for the D.Dimer capture. The bound analyte is then revealed later using the second monoclonal antibody coupled to alkaline phosphatase. The assay is performed in less than 10 minutes and it can be used instantaneously by the clinical laboratories in emergency situations. Only 200 microliters of a standard citrated plasma are required. All samples containing more than 0.5 micrograms/ml D.Dimer produce a color development which intensity is a relation of the D.Dimer concentration. All specimen with levels below 0.3 micrograms/ml give negative tests, whereas a grey zone is present between 0.3 and 0.5 micrograms/ml. This assay offers all the specifications required by its applications to the exclusion diagnosis of deep vein thrombosis and pulmonary embolism.

Diagnosis of deep vein thrombosis

In this chapter, various tests have been discussed in the diagnosis of DVT and have been classified according to various patient categories. To summarize, the following guidelines may be of clinical use in the management of patients with suspected DVT. Acute, First Event of Suspected DVT These patients often suffer from occluding, proximal thrombi. Therefore, noninvasive tests such as CUS or IPG are most suitable for these patients. If an abnormal CUS or IPG result is found, the diagnosis is virtually proven, and this may serve as a basis to treat the patient with anticoagulants. If a normal CUS or IPG result is obtained, serial testing is indicated to detect extending calf vein thrombi or nonoccluding DVT, which becomes occlusive at follow up. Anticoagulants may be withheld safely if the test remains normal within 1 week. Acute, Recurrent Suspected DVT These patients may have residual thrombi present, which makes the noninvasive tests (CUS/IPG) less useful. However, if a normal noninvasive test was documented previous to the acute recurrent event, this test may be used. If an abnormal test result is found in the presence of a documented, normal previous-test outcome, this may serve as a basis for anticoagulant therapy. Although no formal studies have been performed to evaluate the safety of withholding anticoagulants if a normal CUS or IPG result is obtained, serial testing is likely to be adequate in these circumstances. Phlebography is the only truly evaluated approach, and this could be considered in all suspected recurrent DVT. Furthermore, contrast venography is the test of choice to discern acute from old thrombi. Asymptomatic DVT in High-Risk Patients The majority of these thrombi are mostly localized in the calf veins only and are often nonocclusive. This makes noninvasive tests unreliable for their detection. Therefore, only contrast venography should be used in this patient category.

Can laboratory testing improve screening strategies for deep vein thrombosis at an emergency unit?

OBJECTIVES

To study various markers of blood coagulation and fibrinolysis in relation to the extension of deep vein thrombosis (DVT), and to compare the diagnostic usefulness of these markers as screening tests for excluding DVT.

DESIGN

A clinical study of patients admitted to an emergency unit.

SETTING

Ostra Hospital, Göteborg, Sweden.

SUBJECTS

One hundred and five patients with a clinical suspicion of DVT.

MAIN OUTCOME MEASURES

Phlebography was used as the reference method for a diagnosis of DVT. Small distal thromboses as well as large proximal thromboses were included. Plasma D-dimer as well as other markers of coagulation and fibrinolysis were analysed.

RESULTS

Twenty-eight proximal and 20 distal DVTs were found. Plasma D-dimers (one ELISA and two latex assays), fibrin monomer, prothrombin fragment 1 + 2 (F1+2), thrombin-antithrombin III complex (TAT) and the t-PA-PAI-1 complex were all significantly correlated to the extension of DVT, whilst fibronectin, tissue-type plasminogen activator (t-PA), single-chain urokinase-type plasminogen activator (scru-PA) and plasminogen activator inhibitor 1 (PAI-1) were not. The sensitivity was 94% for the D-dimer ELISA and one of the latex methods (latex-B), at a specificity of 60% and 68%, respectively. The negative predictive value was 92% for ELISA and 93% for latex-B, and both assays showed a negative predictive value of 100% for proximal DVTs. Fibrin monomer, F1+2, TAT, D-dimer (latex-S) and the t-PA-PAI-1 complex all showed lower negative predictive values (88, 84, 79, 78 and 65% respectively).

CONCLUSIONS

Sensitivity and negative predictive values for a latex assay (D-dimer latex-B) was similar to that of a D-dimer ELISA: With a sensitivity of 94% (100% for proximal DVTs) such a latex assay may be included in a screening strategy for DVT at an emergency unit. However, the safety of such an approach has to be tested in other prospective studies.

Plasmatic parameters of fibrin formation and degradation in cancer patients: correlation between fibrinopeptide A and D-dimer

This investigation was carried out to evaluate fibrin formation and degradation in various types of solid neoplasms by measuring fibrinopeptide A (fpA) in the plasma with a radioimmunoassay and D-dimer (DD) with an enzyme-linked immunosorbent assay in 176 cancer patients; 77 of them showed signs of distant metastasis (M1). FpA and DD were abnormally elevated in 81 and 143 patients respectively. FpA and DD were significantly correlated and unrelated to plasma fibrinogen. Both fpA and DD levels were more elevated in M1 than M0 patients. Coumarin anticoagulants, administered to 32 patients of our series with the aim of preventing cancer growth and dissemination, caused a significant decrease both in fpA and DD levels. Our data provide evidence of increased in vivo fibrin formation and degradation in solid neoplasms: oral anticoagulants can modulate cancer-related hypercoagulation.

Failure of thrombin-antithrombin III complexes in the diagnosis of deep vein thrombosis

Plasma thrombin-antithrombin III (T-AT) complexes are reputed to be an indirect manifestation of thrombin generation, and a role for their determination in the diagnosis of deep vein thrombosis (DVT) has been advocated. In order to evaluate the accuracy of T-AT complexes assay for DVT diagnosis, in 166 consecutive outpatients with clinical suspicion of the disease, plasma concentration of T-AT complexes was measured immediately before venography by means of an enzyme-linked immunosorbent assay kit. The result of the T-AT complexes assay was elevated in 29 of the 48 patients with DVT (sensitivity, 60%). The T-AT complexes levels were within the normal range in 104 of the 118 patients with normal venograms (specificity, 88%). The positive and the negative predictive value were 67% and 85%, respectively. The authors conclude that the T-AT complexes assay is of little value for the diagnosis of DVT in outpatients.

Thrombosis in spinal cord injury

Some traditional coagulation assays and several new molecular markers of hemostatic activation were measured in 37 patients with spinal cord injury (SCI). Twenty one of the patients (57%) developed deep vein thrombosis (DVT). The radiofibrinogen uptake test (RFUT) was used to diagnose DVT. Thirty eight percent of quadriplegic and 88% of paraplegic patients developed DVT (p < 0.005). No significant differences were found in platelet counts, mean platelet volumes, fibrinogen levels, von Willebrand factor (Ag) levels, platelet factor 4 and beta thromboglobulin concentrations between the groups with and without DVT. Fibrinopeptide A, thrombin/antithrombin III (TAT) complexes and plasma D-dimer levels were significantly higher in the patients with thrombosis. Most patients with DVT had elevated TAT complex levels up to three days before the RFUT became positive. D-dimer levels were highest after the diagnosis had been made.

Persistent generation of thrombin after acute myocardial infarction

During the acute phase of myocardial infarction, the generation of thrombin is reflected in the sudden rise of fibrinopeptide A (FPA) and the thrombin-antithrombin III (TAT) complex in blood. We have systematically determined the FPA and TAT plasma concentrations over a period of 14 days after acute myocardial infarction in 100 patients. Mean levels of both thrombin markers were the highest on admission, remained elevated over the following few days, and then gradually declined after day 5. Still, by the end of the first week two thirds of the patients had distinctly elevated TAT and FPA levels, and by the end of the second week such an abnormality was present in half of them. Continuous intravenous heparin infusion at a dose of 20,000 units/day, administered for 1 week to patients who had either received (n = 21) or not received (n = 17) streptokinase, led to a significant depression (p less than 0.05) of thrombin markers over the first 48 hours, an effect that did not persist over the subsequent days of treatment. In patients not assigned to heparin treatment, those in heart failure had significantly (p less than 0.05) higher mean TAT and FPA values on days 3, 5, and 7 compared with patients in whom heart failure was absent. Infarct extension, pulmonary embolism, and death were also associated with a rise in one or both thrombin markers, often preceding the onset of clinical symptoms. Thrombinogenesis was not accompanied by changes in mean plasma concentrations of prothrombin, antithrombin III, or alpha 2-macroglobulin.(ABSTRACT TRUNCATED AT 250 WORDS)