The Utility of activated Partial Thromboplastin Time (aPTT) Clot Waveform Analysis in the Investigation of Hemophilia A Patients with very Low Levels of Factor VIII Activity (FVIII:C)

Abstract

SummaryThe lower detection limit of the conventional one-stage aPTT based clotting assay for determining FVIII:C levels is generally 1.0-2.0 IU/dl. Consequently, it has been impossible to study the clinical significance of levels of FVIII:C less than 1.0 IU/dl. Using a photo-optical automated coagulation analyzer, the Organon Teknika MDA II®, we have performed qualitative and quantitative aPTT waveform analysis and measured FVIII:C levels by automated one-stage aPTT clotting assay in 36 severely affected Hemophilia A patients. Qualitative waveform analysis showed clear evidence of individual differences in the waveform profile suggesting differing coagulant activity from patient to patient. The FVIII:C level was less than 0.2 IU/dl in 23 cases and levels of FVIII:C between 0.2 and 1.0 IU/dl could be discriminated in 13 patients. The FVIII:C level in these patients was closely correlated with the minimum value of the second derivative of the aPTT waveform (Min2). This is a measure of the acceleration of change in optical transmission at the initiation of coagulation. Furthermore, the correlation of the aPTT (time and Min2) and the FVIII:C level, determined by a one-stage clotting assay on the same system, was high in plasmas with a range of levels of FVIII:C artificially prepared by the addition of various concentrations of rFVIII:C to FVIII deficient plasma. These data suggest that it is possible to segregate different levels of clotting activity in patients previously assigned to a single grouping, i.e. less than 1.0 IU/dl, by conventional one-stage assay. Thus clot waveform analysis may be useful for the investigation of the clinical phenotype of individual patients and their response to therapy.

Clot waveform analysis for perioperative hemostatic monitoring in a hemophilia A patient on emicizumab undergoing liver transplantation

“…It is consistent with previous reports that maximum coagulation velocity and acceleration better correlated with FVIII activity than APTT [7,15]. The plateaus of these CWA parameters appearing at FVIII activity of 100% or more seem to support the protocol for perioperative FVIII replacement [10].…”

“…Several studies on CWA applied to assessing hemostasis in patients with liver diseases or those with hemophilia have been reported [14,15]. Recently, CWA has been used in evaluating the changes in procoagulant and anticoagulant activities in a patient after liver transplantation for congenital protein C de ciency [16].…”

Phenotypic variation in severe hemophilia A is related to endogenous thrombin potential and plasma levels of factor VII

“…Patients diagnosed with severe hemophilia show considerable variability in the number of bleeding episodes and may have a mild disease phenotype [2][3][4]14]. Variable levels of FVIII activity below 1%, the pharmacokinetics of the infused FVIII, the type of mutation in F8 gene and the concomitant presence of prothrombotic factors have been associated with the variable phenotype of severe hemophilia A [5][6][7][8]15,16].…”

The Reevaluation of Thrombin Time Using a Clot Waveform Analysis

“…A clot waveform analysis (CWA)-APTT [ 13 , 14 ] and small-amount tissue factor (TF)-induced FIX activation (sTF/FIXa) assay [ 14 , 15 ] can show the peak time and peak height, allowing the evaluation of thrombin burst to be performed as easily as a routine assay. The CWA-APTT has been reported to detect very low levels of FVIII activity in patients with hemophilia A [ 16 ], and has proven useful for the differential diagnosis of hemophilia, acquired hemophilia A, lupus anticoagulant (LA), and DIC, as well as monitoring the results of anticoagulant therapy or bypass therapy in patients with FVIII inhibitors [ 17 , 18 , 19 , 20 , 21 ].…”