Rubber. Estimation of uncertainty for test methods. Non-functional parameters

SummaryWe have prospectively evaluated the biologic response to desmopressin (DDAVP) in 28 children with type 2 von Willebrand disease (VWD) in correlation with the phenotype and the molecular defect of VWF. The diagnosis of VWD type 2 was mainly based on VWF functional parameters and/or an aberrant VWF multimer pattern. Seventeen different mutations were identified (6 of them novel). No response with respect to the functional parameters VWF:RCo and/or VWF:CB was seen in patients with severe abnormality of the VWF multimer pattern. One patient with VWD type 2A phenotype IIC Miami did not respond with respect to VWF:CB, but showed a good response of VWF:Ag and FVIII:C as expected. Interestingly he showed a persistently high level of VWF:Ag and FVIII:C up to 4 hours after DDAVP infusion. Patients with minor alterations of multimer structure and particular mutations responded well to DDAVP, whereas patients with normal multimer structure but a defect in platelet dependent functional parameters did not respond with VWF:RCo. Conclusion: Children with VWD type 2 show a variable response to desmopressin depending on the mutation that correlates with the functional defect and the presence or absence as well as the half-life of large VWF multimers. Our data emphasize the usefulness of DDAVP testing even in patients with VWD type 2, possibly with the exception of VWD type 2B.

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Scientific and Standardization Committee Communications Comparison of Test Methods for the Lupus Anticoagulant: International Survey on Lupus Anticoagulants-I (ISLA-1)

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647340 ◽

1990 ◽

Vol 64 (03) ◽

pp. 478-484 ◽

Cited By ~ 28

Author(s):

Thomas Exner ◽

Douglas A Triplett ◽

David A Taberner ◽

Margaret A Howard ◽

E Nigel Harris

Keyword(s):

Lupus Anticoagulant ◽

Test Methods ◽

Positive Sample ◽

Direct Proportion ◽

Clotting Time ◽

Preliminary Screening ◽

Activated Platelets ◽

Tissue Thromboplastin ◽

Kaolin Clotting Time ◽

Induced Defects

SummarySix lyophilized plasma samples were sent to 20 “expert” laboratories for assessment of lupus anticoagulant (LA). Four samples contained pooled LA of graded potency mixed with aged normal plasma. One contained LA plus cephalin phospholipid and one contained a nonspecific venom anticoagulant. Sixteen methods were used overall with some participants using up to 8 methods. Results were scored in regard to the known potencies of LA in the samples and other known induced defects.Activated partial thromboplastin time (APTT) tests used by most participants for preliminary screening were relatively sensitive, but non-specific. Platelet or phospholipid neutralization procedures (PNP) appeared to be sensitive and specific but showed a non-linear response to increased LA content. Kaolin clotting time (KCT) tests showed the most sensitive response to increased LA content but the weaker LA were not scored as abnormal by most laboratories as the samples may have contained platelet fragments. Other commonly used tests such as the tissue thromboplastin inhibition (TTI) test and the dilute Russell’s viper venom test (DRVVT) were carried out somewhat inconsistently. The variability in performance of tests in different laboratories indicates that standardization of methodology is urgently required.Generally it seemed that most clotting tests were “bypassed” by the addition of phospholipid to a known LA-positive sample in apparently direct proportion to their sensitivity. Sample preparation, especially prevention of contamination with activated platelets is a vital preliminary part in the assay of LA.

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