1. FRETS-VWF73 rather than CBA assay reflects ADAMTS13 proteolytic activity in acquired thrombotic thrombocytopenic purpura patients.
- Author
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Mancini I, Valsecchi C, Lotta LA, Deforche L, Pontiggia S, Bajetta M, Palla R, Vanhoorelbeke K, and Peyvandi F
- Subjects
- ADAMTS13 Protein, Humans, Predictive Value of Tests, Protein Binding, Protein Denaturation, Proteolysis, Purpura, Thrombotic Thrombocytopenic blood, Purpura, Thrombotic Thrombocytopenic enzymology, Registries, Reproducibility of Results, Urea chemistry, ADAM Proteins deficiency, Collagen metabolism, Fluorescence Resonance Energy Transfer, Purpura, Thrombotic Thrombocytopenic diagnosis, von Willebrand Factor metabolism
- Abstract
Collagen-binding activity (CBA) and FRETS-VWF73 assays are widely adopted methods for the measurement of the plasmatic activity of ADAMTS13, the von Willebrand factor (VWF) cleaving-protease. Accurately assessing the severe deficiency of ADAMTS13 is important in the management of thrombotic thrombocytopenic purpura (TTP). However, non-concordant results between the two assays have been reported in a small but relevant percentage of TTP cases. We investigated whether CBA or FRETS-VWF73 assay reflects ADAMTS13 proteolytic activity in acquired TTP patients with non-concordant measurements. Twenty plasma samples with non-concordant ADAMTS13 activity results, <10% using FRETS-VWF73 and ≥20% using CBA, and 11 samples with concordant results, <10% using either FRETS-VWF73 and CBA assays, were analysed. FRETS-VWF73 was performed in the presence of 1.5 M urea. ADAMTS13 activities were also measured under flow conditions and the VWF multimer pattern was defined in order to verify the presence of ultra-large VWF due to ADAMTS13 deficiency. In FRETS-VWF73 assay with 1.5 M urea, ADAMTS13 activity significantly increased in roughly 50% of the samples with non-concordant results, whereas it remained undetectable in all samples with concordant measurements. Under flow conditions, all tested samples showed reduced ADAMTS13 activity. Finally, samples with non-concordant results showed a ratio of high molecular weight VWF multimers higher than normal. Our results support the use of FRETS-VWF73 over CBA assay for the assessment of ADAMTS13 severe deficiency and indicate urea as one cause of the observed differences.
- Published
- 2014
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