Bridging laboratory assays, genetics, and clinical phenotypes in antithrombin deficiency : rethinking the diagnostic paradigm

Rojnik, Tamara (author), Šket, Robert (author), Slapnik, Barbara (author), Vrhovšek, Blaž (author), Mavri, Alenka (author), Debeljak, Maruša (author), Božič Mijovski, Mojca (author)

Background Diagnosis of antithrombin deficiency (ATD), the most severe inherited thrombophilia, commonly relies on functional assays despite their uncertain sensitivity. Moreover, routine characterization of ATD remains uncommon due to limited supporting clinical data. Objectives This study aimed to evaluate the diagnostic sensitivity of commercial antithrombin (AT) activity assays and assess clinical differences among ATD types to refine the current diagnostic approach. Methods Eighty-eight patients with decreased AT activity and 124 consecutive patients with unprovoked venous thromboembolism were included. AT activity was measured using six assays. Genetic analysis of SERPINC1 was performed by Sanger sequencing and multiplex ligation-dependent probe amplification; additionally, long-read whole-genome sequencing was conducted. Results Fifteen SERPINC1 variants were detected, including two novel ones. AT Padua I (p.Arg79His) was the most prevalent (49%). Sensitivity varied across AT activity assays, particularly for types IIRS and IIHBS, with variant-specific discrepancies. AT Dublin (p.Val30Glu), causing transient deficiency, was undetected by all assays. Two assays demonstrated very high sensitivity (93%; p < 0.001), while two others showed poor sensitivity (46%). Regardless of measured AT activity, characterization of ATD type enabled better risk stratification. Type I was associated with early-onset and recurrent venous thromboembolism, and type IIHBS was distinctly linked to arterial thrombosis. Conclusions Assay sensitivity varies considerably, and only a few proved suitable as first-line tests. Genetic testing for common variants undetectable by even the most sensitive assays, along with ATD characterization, should be integrated into diagnostic algorithms. Our results also suggest that young patients with arterial thrombosis should be screened for ATD.

• Language: English
• Keywords: antithrombin iii deficiency, blood coagulation tests, mutation, thrombophilia
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FFA - Faculty of Pharmacy; MF - Faculty of Medicine
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: 10 str.
• Numbering: Vol. 261, art. 109689
• PID: 20.500.12556/RUL-183691
• UDC: 61
• ISSN on article: 1879-2472
• DOI: 10.1016/j.thromres.2026.109689
• COBISS.SI-ID: 281250819
• Publication date in RUL: 17.06.2026

Record is a part of a journal

• Title: Thrombosis Research
• Shortened title: Thromb. Res.
• Publisher: Elsevier
• ISSN: 1879-2472
• COBISS.SI-ID: 23047685

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Projects

• Funder: University Medical Centre Ljubljana, Department of Vascular Diseases

• Funder: University Medical Centre Ljubljana, University Children's Hospital