Detecting molecular forms of antithrombin by LC-MRM-MS: defining the measurands

Afdeling Klinische Chemie en Laboratoriumgeneeskunde (AKCL

Contribution of clinical chemistry in the diagnostic procedure of deep venous thrombosis

One of the most common cardiovascular disorders in industrialized countries is venous thrombo-embolism (VTE). This disorder has a clinical presentation as deep venous thrombosis (DVT) and/or pulmonary embolism. The common diagnostic workup of patients suspected for VTE according to the guidelines is a combination of the score of a clinical decision rule (CDR), information about the probability, and the level of the D-dimer (DD) fragment, information about the degree of coagulation and the breakdown of the formed clot. In practice, if the CDR and the DD level are normal, it is safe to rule out VTE. In all other cases additional imaging is required. In this thesis we focused on the contribution of clinical chemistry in the diagnostic procedures of outpatients, suspected for DVT, in the exclusion of DVT and a reduction of false-positive results. The performance of several commercial DD assays in terms of sensitivity and specificity was compared. The sensitivity should be as high as possible (100%) to safely exclude and to avoid false-negative results and the wish is have specificity as high as possible to reduce the number of patients with unnecessary additional imaging tests, the false-positive results. None of the DD assays could be used as standalone test. The value of the standard procedure in the diagnostic workup, the combination of CDR score and the DD level was evaluated. The number of patients with a normal CDR decreases with age, just as a normal DD level. The standard algorithm is safe for all ages, but less effective in the elderly. To overcome the age dependence of DD, an early marker of coagulation, the fibrin monomer (FM) was evaluated, for use instead of or combined with the D-dimer assay. It was not possible to use the FM assay as standalone test, but in specific patient groups the number of ultrasonographic examinations can be reduced. The performance of age dependence cut-off values of the DD level was tested; a higher cut-off level results in a higher specificity. With a dichotomous distribution, < 60 y and ≥ 60 y, it is feasible to change the cut-off value by a sensitivity of 100%, with a reduction of false-positive results. The new technique of thrombin generation (TG), which informs us about the coagulation potential, was tested. This technique cannot replace the DD, but has added value in specific patient groups. The performance of the TG assay in patients with inherited or acquired thrombophilic risk factors for VTE is evaluated, the time dependent TG parameters are prolonged in patients with factor V Leiden. Finally we evaluated an assay specific for inflammation dependent fibrinogen degradation product and a second assay, comparable with DD, but with a specific reaction with the D-E fragment. Also these assays could not replace the DD, but offered additional diagnostic value, the first especially in the elderly and the second provided insight in the difference in composition of the fibrin degradation products in DVT positive and negative patients

Harmonization and external quality assessment of antithrombin activity assays

Thrombosis and Hemostasi

An additional bolus of aspirin does not guarantee complete platelet inhibition during PTCA.

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

Item does not contain fulltextBACKGROUND: 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(R) 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(R) 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

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

Item does not contain fulltextBACKGROUND: 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