Laboratory Limitations of Excluding Hereditary Protein C Deficiency by Chromogenic Assay: Discrepancies of Phenotype and Genotype

Autor: Holger Seidel MD, Bianca Haracska BSc, Jennifer Naumann PhD, Philipp Westhofen PhD, Moritz Sebastian Hass MSc, Johannes Philipp Kruppenbacher MD
Jazyk: angličtina
Rok vydání: 2020
Předmět:
Zdroj: Clinical and Applied Thrombosis/Hemostasis, Vol 26 (2020)
Druh dokumentu: article
ISSN: 1938-2723
10760296
DOI: 10.1177/1076029620912028
Popis: Protein C (PC) deficiency is associated with an increased risk for venous thromboembolism (VTE). In daily practice, exclusion of a hereditary PC deficiency is often based on a single determination of PC activity, by either clotting time–based or mostly chromogenic assay. However, diagnosis of hereditary PC deficiency is challenging due to several laboratory and clinical limitations. We compared the potential of PC activity values measured by either chromogenic or clotting time–based assay to predict a variation in the PROC gene. One hundred one (35%) of 287 patients carried variations within the PROC gene, including 2 previously not published variations. In 20 (20%) patients with identified variation, PC activity, determined by chromogenic assay, was within the reference range. For prediction of an underlying genetic defect determined by chromogenic and clotting time–based assay, sensitivity was 80% versus 99%, specificity 75% versus 18%, positive predictive value 64% versus 39%, and negative predictive value (NPV) 88% versus 97%. The lower NPV of chromogenic versus clotting time–based PC assay can be mainly explained by the presence of PC deficiency type IIb. Following our proposed diagnostic algorithm, additional measurement of PC activity by clotting time–based assay in case of a positive VTE history improves detection of this subtype of PC deficiency. Considering potential therapeutic consequences for primary and especially for secondary VTE prophylaxis, genetic analysis is required not only for confirmation but also for clarification of PC deficiency.
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