A thrombin generation assay may reduce the need for compression ultrasonography for the exclusion of deep venous thrombosis in the elderly.

INTRODUCTION: The exclusion of deep venous thrombosis (DVT) by pre-test probability (PTP) and D-dimer in the elderly is safe, but has a low specificity. There is increasing interest in the diagnostic role of thrombin generation in patients with thrombosis. We evaluated the value of thrombin generation in the exclusion of DVT, especially in elderly patients. MATERIAL AND METHODS: All thrombin generation parameters of the Endogenous Thrombin Potential assay were tested retrospectively in a cohort of 443 patients suspected for DVT. The performance of the assay was calculated as AUC of the ROC curve and association with DVT as odds ratio (OR). The lag time value was combined with results of PTP and Innovance D-dimer assay. RESULTS: All thrombin generation parameters had a low AUC. In the 4th age quartile, the corrected OR of lag time increased to 16 and the AUC of lag time for the combination PTP < 2 and D-dimers ≥ 500 µg/L was 0.96 with a cut-off value of 23.0 sec. The exclusion of DVT in patients ≥ 75 years (n = 30), based on this combination and lag time values ≤ 23.0 sec had a NPV of 100% and a specificity of 96.0% in this subgroup of patients and decreased the number needed to test from 10 to 1.1. CONCLUSION: Thrombin generation parameters alone are inappropriate for the exclusion of DVT. However, in the elderly, the current algorithm of exclusion of DVT may improve markedly by the addition of the lag time results of the ETP.

An age-adapted approach for the use of D-dimers in the exclusion of deep venous thrombosis.

A normal D-dimer (DD) concentration for the exclusion of deep venous thrombosis (DVT) has a low specificity in older patients and compression ultrasonography is often required. Three D-dimer assays, STA Liatest, Tina-quant, and Innovance, are evaluated in symptomatic outpatients suspected for DVT with emphasis on its performance in older patients by using different cut-off levels. This study includes 466 outpatients suspected for having DVT. The diagnostic accuracy, measured as sensitivity and area under the curve of the receiver operation characteristic curve is good for all DD assays. The specificity of the DD assays combined with a low pretest probability varies from 42.6 to 51.5%. The specificity of the three DD assays in patients > or = 60 years varies, however, between 24.6 and 40.9%. Several cut-off values in different age-subgroups are studied. For patients < 60 years, the most accurate cut-off value is 500 microg/L for all DD assays. For patients > or = 60 years, a threshold of 750 microg/L has the best results with NPV of 100% for all assays and specificity of 48.5% (STA Liatest), 60.6% (Tina-quant), and 49.2% (Innovance), respectively. For the three assays, the number needed to test (NNT) decreases in both subgroups of patients compared to the standard algorithm. A cut-off level of 750 microg/L for patients > or = 60 years improves the clinical performance of DD assays in combination with the PTP score without the loss of NPV. The NNT improves substantially with an age-adapted algorithm.

The role of fibrin monomers in optimizing the diagnostic work-up of deep vein thrombosis.

Despite the use of a clinical score and D-dimers to exclude deep vein thrombosis (DVT), the majority of patients still need repeated ultrasound (US). The aim of the study was to investigate whether fibrin monomers (FMs), as markers of thrombin generation, have additional value in the diagnosis of DVT. This is a posthoc analysis of 464 outpatients, participants in a management study using D-dimers (Tina-Quant and a clinical score in the exclusion of DVT. Two new FM assays (Auto LIA-FM and IATRO SF, Japan) were performed. Overall sensitivity, negative predictive value (NPV) and specificity of the D-dimer test were 98%, 98% and 42%. The optimal cut-off point for the Auto LIA-FM test was

The influence on INRs and coagulation factors of the time span between blood sample collection and intake of phenprocoumon or acenocoumarol: consequences for the assessment of the dose.

Managing treatment with vitamin K antagonists, the prothrombin time (PT), expressed as international normalized ratio (INR), may not represent the INR during the entire 24 hour (h) period, and this variation may be different between long-acting phenprocoumon and short-acting acenocoumarol. For both drugs we investigated the variation in 24 h of the PT/INR, the consequencesfor the assessment of the doses and which vitamin K-dependent factor causes the daily variation. Patients on self-management took their medication at 6 p.m. and determined their INRs for eight weeks, once a week and three times daily (8.30 a.m., 6 p.m. and 11 p.m., thus 14.5 h, 24 h and 29 h after taking the medication, respectively). Acenocoumarol showed a significant variation in INRs over the 24 h period, with 22 out of 80 INRs >20% lower at 11 p.m. versus 8.30 a.m. Phenprocoumon showed only few variations. Patients managed by the anticoagulation clinic took their medication at 6 p.m. for four weeks and then at 8 a.m. for four weeks, 15 h and 25 h, respectively, before the weekly blood collection. PT/INR and coagulation factors VII, X and II were determined. With acenocoumarol, taken 25 h before blood collection, the INRs were significantly different compared to 15 h, especially attributed to plasma levels of factor VII. Those on phenprocoumon were equal. These variations of INRs during 24 h may have major effects on the prescribed dose of short-acting vitamin K antagonists, such as acenocoumarol, especially for INRs at the limits of the therapeutic ranges.

The predictive value of D-dimer measurement for cancer in patients with deep vein thrombosis.

BACKGROUND AND OBJECTIVES: Venous thromboembolism can be related to malignancy, but routine screening for cancer in patients with deep vein thrombosis (DVT) is not a recommended practice. The aim of this study was to evaluate the value of D-dimer concentration in predicting cancer in patients with DVT. DESIGN AND METHODS: D-dimer levels were measured in outpatients presenting with DVT. In a proportion of patients, D-dimer levels were measured daily for 4 days. The occurrence of malignancy was documented. RESULTS: Patients were followed for a median of 34 months. Fifty (23%) of 218 patients with thrombosis had cancer in the study period including 14 who developed cancer during the follow-up. High initial D-dimer levels (levels > 4000 mg/L) were associated with more cancer during follow-up than were lower D-dimer levels: 13% versus 4% (p=0.048). High D-dimer levels after 4 days of treatment were associated with a 15% prevalence of cancer whereas the prevalence in patients with lower D-dimer levels was 5% (p=0.1). The total cancer prevalence (including cancer diagnosed before thrombosis) in patients with initial D-dimer levels < 4000 mg/L was 16% compared to 32% in patients with higher levels (p=0.009, RR=2.0). After 4 days of treatment, total cancer prevalences were 14% and 46%, respectively (p=0.02, RR=3.4). In patients aged < 60 years, initial D-dimer levels of < 4000 mg/L were associated with a cancer prevalence of 3% whereas higher levels were associated with a prevalence of 23% (p=0.001, RR=8.6). After 4 days of treatment, the prevalences associated with lower and higher levels of D-dimer were 0% and 100%, respectively (p=0.003). There was no difference in older patients. INTERPRETATION AND CONCLUSIONS: High D-dimer concentrations at presentation or during the first days of treatment are indicators of an increased probability of overt or occult forms of cancer, especially in patients under 60 years old.

Markers of inflammation and oxidative stress in exacerbated chronic obstructive pulmonary disease patients.

COPD is characterised by damage to small airways due to an inflammatory process as well as an imbalance between oxidants and antioxidants. Several cytokines and cell adhesion molecules enhancing a mainly neutrophilic inflammation have been associated with COPD. The aim of the study was to investigate whether inflammation or oxidative markers gave an indication of the course of COPD during an exacerbation. Fourteen patients with moderate to severe COPD admitted to the St. Antonius Hospital because of an exacerbation have been monitored during treatment with prednisolone 50 mg intravenously during 24 h at admission, reduced to 25 mg at day 3 and tapered off with oral prednisolone at day 7. On three separate occasions, day 1, 3 and 7, H2O2 in exhaled air, IL-8 and the soluble cell adhesion molecule sICAM and sE-selectin in serum were measured. We compared the patients at day 1 with healthy controls (in both non-smokers and smokers). Furthermore, we examined the changes from the study group in time during therapy. At admission all the markers were raised in comparison with the control groups. During treatment H2O2 concentrations in breath condensate declined significantly (P<0.001) as well as IL-8 and sICAM in serum (P=0.002, respectively, P<0.001). There was no significant change in sE-selectin (P=0.132). No significant improvement has been found in spirometry. These data suggest that the markers H2O2 in exhaled air, IL-8 and sICAM in serum are suitable markers in monitoring exacerbated COPD.

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.

Pretreatment with oral anticoagulants decreases platelet activation in patients before and after percutaneous coronary intervention.

BACKGROUND: Platelet activation plays a major role in acute vessel closure after coronary angioplasty. In the randomized Balloon Angioplasty and Anticoagulation Study (BAAS), pretreatment with oral anticoagulants in addition to aspirin resulted in a 47% reduction of acute complications as compared with aspirin alone. This result may suggest a direct effect of oral anticoagulants on platelet activation. METHODS AND RESULTS: Patients were randomized to aspirin alone (group A, n = 26) or to aspirin plus oral anticoagulants started one week before angioplasty (group B, n = 26). Platelet response tests were performed 1 hour before (baseline) and 1 hour after intervention and on day 1. Platelet activation was measured by flow cytometry, as the number of antibody-positive platelets per 10,000 counted. Platelet function was evaluated with use of the PFA-100 analyzer. In group B, the median number of P-selectin-positive platelets was lower before (28 vs. 54, P = 0.018) and after (13 vs. 24, P = 0.377) angioplasty than in group A. Also the median decrease in the number of P-selectin-positive platelets during angioplasty was lower in group B (delta = 4) than in group A (delta = 30, P = 0.022). No further significant change was observed in platelet activation on day 1 in the two groups. The ability of platelets to become stimulated as measured with the PFA-100 analyzer was not affected by oral anticoagulants. CONCLUSIONS: Pretreatment with oral anticoagulants resulted in less activated platelets before and after coronary angioplasty, which is in agreement with its clinical effect of reducing procedural complications. Platelet function was not affected by oral anticoagulants.

Thrombosis and hemorrhage in heparin-induced thrombocytopenia in seriously ill patients.

OBJECTIVE: Heparin-induced thrombocytopenia (HIT) is the most common form of drug-induced immune-mediated thrombocytopenia. HIT may be aggravated by life-threatening arterial and venous thrombosis and, to a lesser extent, hemorrhagic complications. We investigated the incidence of thromboembolic and hemorrhagic complications in critically ill patients with the multiple organ dysfunction syndrome and HIT. DESIGN: Case-control study. SETTING: A 33-bed general intensive care unit in a university-affiliated teaching hospital. PATIENTS: Twenty consecutive patients with laboratory-proven HIT compared with 20 contemporary, consecutive patients without HIT. INTERVENTIONS: Unfractionated heparin or low-molecular-weight heparin were replaced by danaparoid sodium in patients with HIT. MEASUREMENTS AND RESULTS: Heparin-induced thrombocytopenia was proven by a positive platelet aggregation test. The HIT group consisted of 14 males and 6 females aged 65.2+/-10.8 years (mean +/- standard deviation) with APACHE II scores of 26.7+/-5.4. Thrombocytopenia less than 100 x 10(9)/l developed within 6.4+/-7.0 days. In 12 patients thrombocytopenia resolved after discontinuation of unfractionated heparin in 8.8+/-6.4 days. Arterial and venous thromboembolic complications occurred more frequently in HIT patients than in non-HIT patients (10/20 (50%) versus 0/20 (0%); chi-square p<0.001). Hemorrhagic complications also occurred more frequently in HIT patients than in non-HIT patients (17/20 (85%) versus 7/20 (35%); chi-square p=0.001). CONCLUSION: In critically ill patients with HIT, the incidence of thromboembolic complications and hemorrhagic complications was remarkably high.

High-dose aspirin in addition to daily low-dose aspirin decreases platelet activation in patients before and after percutaneous coronary intervention.

BACKGROUND: Activated platelets play a major role in acute vessel closure after coronary angioplasty. Although aspirin is the routine therapy during angioplasty, it only incompletely prevents acute closure. This might be due to suboptimal dosing. OBJECTIVE: First, to study the effect of additional high-dose aspirin on platelet activation during coronary angioplasty. Second, to assess the potential of the new PFA-100 analyzer to evaluate the effect of different doses of aspirin in patients undergoing angioplasty. METHODS: Fifty-one patients on 100 mg aspirin/day for at least 1 month were randomized to continuation of 100 mg aspirin/day only (Group A=24 patients), or to this regime plus a bolus of 1000 mg of aspirin given 1 day before angioplasty (Group B=27 patients). Results were compared with 15 controls. Platelet function was measured before angioplasty by the PFA-100 analyzer; platelet activation was measured by flow cytometry just before and 1 h after angioplasty. RESULTS: At baseline, Group A had significantly more activated platelets than the control group (P<.001). High-dose aspirin in Group B resulted in significantly lower platelet activation as compared with both controls (P<.001) and Group A (P<.001). During angioplasty, the number of activated platelets decreased significantly in Group A (P<.001), while there was no change in Group B (P=.6). The PFA-100 analyzer was unable to detect differences between the two treatment groups. CONCLUSIONS: The addition of high-dose aspirin to daily low-dose aspirin, 1 day before coronary angioplasty, significantly reduced the platelet activation state before and after intervention. The PFA-100 analyzer did not detect differences in the effect of low- versus high-dose aspirin on platelet function.

Diagnostic possibilities of specific fibrin(ogen) degradation products in relation to venous thromboembolism.

The exclusion of deep venous thrombosis (DVT) in the elderly is hampered by low specificity in clinical decision of D-dimer assays in older patients. To reduce false-positive results, we evaluated specific fibrin(ogen) degradation product assays for their contribution in the diagnosis of DVT. In a post-hoc study with outpatients suspected for DVT, we evaluated the elastase-specific fibrinogen (fibrinogen elastase degradation product, FgEDP) and D-E-specific fibrin (fibrin degradation product, FbDP) degradation product assays in relation to DVT. Results were combined with five D-dimer assays as ratio, with a specific focus on age-dependency. In 437 patients (DVT prevalence 39%), FgEDP correlated with D-dimer in DVT-negative patients (P<0.001), but not in DVT-positive patients (P > 0.55). FbDP results correlated with D-dimer in both groups (P<0.001). The values of the area under the curve of the receiver operating characteristic curve for both assays were lower than D-dimer. Using the ratios, only in the fourth age quartile D-dimer/FgEDP ratios had diagnostic value with lower number needed to test (1.8-12.7) as compared to D-dimer less than 500 µg/l alone (5.4-102). The D-dimer/FbDP ratios in DVT-negative elderly patients increased to a plateau by increasing D-dimer. In DVT-positive patients, these ratios were near constant for increasing values of D-dimer. In elderly patients, the D-dimer/FgEDP ratios may improve the number of patients in whom DVT could be excluded. The D-dimer/FbDP ratios showed differences in composition of fibrin degradation products between DVT-negative and DVT-positive patients and between young and old DVT-negative patients.

Harmonization and external quality assessment of antithrombin activity assays.

UNLABELLED: In the framework of a Dutch project named "Calibration 2000" harmonization of antithrombin activity assays was studied. The commutability of potential calibrators for antithrombin was assessed by means of a twin-study design, which is a multicentre, split-patient sample, between-field-methods protocol. The twin-study consisted of simultaneous analysis of fresh-frozen patient plasmas and three potential calibrators for antithrombin by 30 Dutch laboratories forming 15 couples. The state-of-the-art intralaboratory standard deviation (SD(SA)) was used to assess the commutability of the potential calibrators. The regression line residuals for the potential calibrators were normalized by expressing them as multiples of SD(SA). All residuals of the potential calibrators were within the 3×SD(SA) limit. One potential calibrator was used in an attempt to harmonize antithrombin assay results in a Dutch field study. The interlaboratory coefficient of variation (CV) of the antithrombin results for three test samples could be reduced from 6.9 - 13.2% (before harmonization) to 5.6 - 9.8% using the common calibrator. CONCLUSION: The potential calibrators were commutable. Limited harmonization was achieved by using a common calibrator for all participants.

Patients with deep venous thrombosis and thrombophilia risk factors have a specific prolongation of the lag time in a chromogenic thrombin generation assay.

The objective of the present study was to evaluate the influence of thrombophilia risk factors on variables of a chromogenic thrombin generation assay (ETP) in a setting with acute deep venous thrombosis (DVT) and non-DVT patients. In 152 outpatients suspected for DVT, the results of thrombophilia investigations were known. In all patients, thrombin generation parameters were determined and related to the presence of thrombophilia risk factors. The thrombin generation results were divided in quartiles to calculate the odds ratio, as a measure of the association with thrombophilia risk factors, corrected for age and sex. The groups with and without DVT were analysed independently. From the 152 patients, there were 108 patients with and 44 without DVT. In the DVT-positive group, lag time was significantly prolonged (21.9 versus 20.3 s; P=0.021) in patients with known thrombophilia risk factors (n=48). The odds ratio for thrombophilia risk factors was 3.7 (95% CI 1.1-12) uncorrected and 4.3 (95% CI 1.2-16) corrected for age and sex, both P values less than 0.05. No differences in ETP parameters were observed in patients without DVT with known thrombophilia risk factors (n=32). The relationship of thrombophilia risk factors with the occurrence of a prolonged lag time in the acute phase of DVT is a new finding. Increased coagulation activation may be the consequence of the thrombophilia risk factors with this observation. To unravel whether the test expresses increased consumption or increased release of anticoagulant factors may open new ways to develop diagnostic methods to add to further refinement of exclusion algorithms for DVT.

Harmonisation of factor VIII:C assay results: study within the framework of the Dutch project 'Calibration 2000'.

In a Dutch project for harmonisation of factor VIII coagulant activity (FVIII:C) assays, the commutability of potential calibrators for FVIII:C was assessed by means of a 'twin-study design', which is in essence a multi-centre, split-patient sample, between-field-methods protocol. Commutability was defined as the degree to which a material yielded the same numerical relationships between results of measurements by a given set of measurement procedures as those between the expectations of the relationships for the same procedures applied to those types of material for which the procedures were intended. The study consisted of the simultaneous analysis of fresh frozen patient plasmas and three potential calibrators for FVIII:C by 16 Dutch laboratories forming eight couples. The state-of-the-art intra-laboratory standard deviation was used to assess the commutability of the potential calibrators. One potential calibrator was used to harmonise FVIII:C assay results in a Dutch field study. The inter-laboratory coefficient of variation of two test samples could be reduced significantly, but no significant effect was observed with three other test samples. We recommend that at least three different sample dilutions be used in each FVIII:C assay, in agreement with previous recommendations.

Reduced efficacy of clinical probability score and D-dimer assay in elderly subjects suspected of having deep vein thrombosis.

The combined strategy of a pretest clinical probability (PCP) score and D-dimer has shown to be of value in the diagnosis of deep vein thrombosis (DVT). As D-dimer concentrations increase with age, the effect of age on the usefulness of this strategy was retrospectively investigated in outpatients suspected of having DVT. In all patients, participants of a prospective management trial, a PCP score and D-dimer (Tina-quant) were performed. In a total of 812 patients, 317 (39%) had thrombosis. Patients were divided into quartiles according to their age. Sensitivity and negative predictive value of a low/moderate PCP score and a normal D-dimer were 98-100% and did not differ between the different age quartiles. Specificity in the highest quartile was 17.4% compared with 49.2% in the youngest (P < 0.000001). The proportion of patients with a low/moderate PCP score and a normal D-dimer decreased with age: 12% in the highest quartile (>73.8 years) versus 25% in younger patients (P = 0.00005). We therefore conclude that the combined strategy of a low/moderate PCP score with a normal D-dimer test is safe for excluding DVT in all age groups, but is less useful in the elderly.

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.