Clot characterization by multidisciplinary approach: biochemical and imaging parameters in a hypocoagulative setting. A pilot study.

BACKGROUND: Clot characterization is, to the present days, a multimodal approach: scanning the clot by electron microscopy (SEM) is helpful for the visualization of fibrin structure along with laboratory parameters such as the clot waveform analysis (CWA) and thrombin generation in different settings of clot abnormalities. This study aimed to assess whether the coagulative parameters were consistent with the clot images texture acquired by SEM, and therefore to propose a more generalist and integrative approach to clots classification. DESIGN AND METHODS: In this pilot study, the examined population consists of eight healthy subjects, seven patients affected by Acquired Hemophilia A (AHA) and seven patients treated with Vitamin K Antagonists (VKAs), similar for age and gender. We studied the velocity and acceleration (1st and 2nd derivative of the aPTT) of clot formation (CWA), the thrombin generation, and the clots' scanning by SEM. Images acquired with SEM were then analyzed with the MATLAB software with the "Texture Analysis" methods to perform classification. Among the various texture parameters, we reported Contrast and Energy. RESULTS: Significant differences among healthy subjects, patients with AHA and those treated with VKAs were detected for the coagulative parameters. We found no differences between VKAs and AHA patients. Contrast and energy highlighted a significant difference among the three groups in agreement with the laboratory's parameters. We found no significant differences between VKAs and AHA patients. CONCLUSIONS: The use of SEM, CWA and thrombin generation parameters may be a starting point for studies aimed to demonstrate the general characteristics of clot formation in different clinical conditions with a multiparametric approach.

A Sardinian Family with Factor XI Deficiency.

INTRODUCTION: Factor XI (FXI) deficiency is a bleeding disorder which causes a bleeding tendency after trauma or surgery. An inhibitor may be acquired secondary to replacement therapy. AIM: To study on genetical and functional grounds a family admitted to our Haemostasis and Thrombosis Centre for an incidental finding of a prolonged activated partial thromboplastin time (aPTT) in three members. METHODS: aPTT mixing test, dosage of FXI activity and antigen, FXI inhibitor titration, DNA analysis and clot waveform analysis (CWA) were performed. RESULTS: Patients II.1, II.3 and II.4 showed a severe FXI deficiency (0.7, 0.7 and 1.8%, respectively) and low antigen level. Since the proposita was already treated with plasma, the dosage of the inhibitor was determined to be 6.4 Bethesda units. They were homozygous for the p.Glu117Stop mutation. The other family members were heterozygous. The velocity and the maximum acceleration of the clot formation were lower than those of the other family members and the normal subjects but higher than those of patients with acquired haemophilia A. CONCLUSION: A mixing test of a prolonged aPTT should be performed because it will be present both in patients with or without the inhibitor. A molecular analysis in severe FXI deficiency is warranted as it may have prognostic significance. CWA may be helpful for better understanding the pathophysiology of this kind of defect.

High frequency of inadequate test requests for antiphospholipid antibodies in daily clinical practice.

BACKGROUND: We have empirically noted that many physicians routinely request anti-phospholipid antibodies (aPL) without a correct clinical indication. The aim of this study was to evaluate retrospectively whether aPL testing at our Thrombosis Centre was justified. METHODS: Medical records from 520 subjects for aPL screening tests for various clinical conditions were reviewed. The aPL screening tests were: lupus anticoagulant (LA), anti-cardiolipin antibodies (aCL) and anti-ß(2) glycoptotein I (aß(2) GPI). Requests for aPL screening were divided into justified, potentially justified or not adequately justified. RESULTS: aPL testing requests were considered justified in 358 (69%) patients, potentially justified in 66 (12.6%) and not adequately justified in 96 (18.4%). LA was positive in 65 (18%) of justified requests and in only one (1%) of the 96 potentially justified requests. None of the 66 not adequately justified for aPL testing was positive for LA. aß(2) GPI was positive in 63 (17.6%) of the 358 justified, in four (6%) of the 66 potentially justified and in five (5.2%) of the 96 not adequately justified requests; aCL IgG were positive in 59 (16.4%) of the 358 justified and in five (7.5%) and six (6.2%) of the potentially justified and not adequately justified requests, respectively. The presence of the triple aPL positivity was found exclusively in the justified requests. CONCLUSIONS: This study suggests that requests for aPL tests should be addressed more adequately. This work could be an example of how to focus attention on requests for laboratory tests especially on the basis of valid clinical criteria before the analyte is measured.