Genotype vs laboratory phenotype correlation of defects in natural anticoagulants in patients with venous thromboembolism
Christine Van Laer1,2 ∙ Marthe Vanrenterghem2 ∙ Marc Jacquemin1,2 ∙ Andreas Verstraete1 ∙ Sarissa Baert3 ∙ Cyrielle Kint3 ∙ Mirjam Kruijt4 ∙ L. Renee Ruhaak4 ∙ Veerle Labarque1,5 ∙ Thomas Vanassche1,6 ∙ Peter Verhamme1,6 ∙ Kathelijne Peerlinck1 ∙ Kathleen Freson1
1) Department of Cardiovascular Sciences, Center for Molecular and Vascular Biology, University of Leuven, Leuven, Belgium
2) Clinical Department of Laboratory Medicine, University Hospitals Leuven, Leuven, Belgium
3) Center for Human Genetics, University Hospitals Leuven, Leuven, Belgium
4) Department of Clinical Chemistry and Laboratory Medicine, Leiden University Medical Center, Leiden, Netherlands
5) Department of Pediatric Hemato-Oncology, University Hospitals Leuven, Leuven, Belgium
6) Department of Cardiovascular Diseases, Thrombosis, Haemostasis, and Vascular Medicine, University Hospitals Leuven, Belgium
Abstract
Background
Plasma-based assays or multigene panel testing can be used for the diagnosis of inherited venous thromboembolism (VTE). Our recent multigene panel data showed strictly concordant results between genetic and phenotypic laboratory testing in only half of the patients.
Objectives
We aimed to evaluate in detail the correlation between genotype and laboratory phenotype for defects in natural anticoagulants.
Methods
Gene panel test results were compared with standard thrombophilia laboratory assay data, including protein C, protein S, and antithrombin plasma activity or antigen levels. We performed additional functional protein C and protein S clot-based assays and mass spectrometry for the detection of antithrombin molecular proteoforms.
Results
We detected PROC, PROS1, or SERPINC1 variants in 110 of 317 patients with VTE of which 61% were (likely)pathogenic variants. Oligogenic inheritance was present in 33% of all patients. Correlation studies showed that not all variants were associated with reduced plasma activity levels, while 14%, 20%, and 5% of our patients with VTE but without a genetic variant had reduced levels for protein C, protein S, and antithrombin, respectively. Additional clot-based assays could diagnose additional patients but not all. Mass spectrometry–based antithrombin assay was able to detect SERPINC1 missense variants in plasmas that were associated with normal antithrombin activity levels.
Conclusions
Thrombophilia screening using plasma-based assays can lead to potential diagnostic misclassification. In contrast, multigene panel testing is more sensitive but still associated with the detection of variants of uncertain significance. Additional studies are required to clarify the role of panel testing for inherited VTE and the impact of oligogenic inheritance.