Dynamic APTT parameters: applications in thrombophilia

Authors

  • B. SØRENSEN,

    1. Haemostasis Research Unit, Centre for Haemostasis and Thrombosis, Guy’s and St Thomas’ NHS Foundation & King’s College London School of Medicine, London, UK
    2. Centre for Haemophilia and Thrombosis, Aarhus University Hospital, Skejby, Denmark
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  • J. INGERSLEV

    1. Haemostasis Research Unit, Centre for Haemostasis and Thrombosis, Guy’s and St Thomas’ NHS Foundation & King’s College London School of Medicine, London, UK
    2. Centre for Haemophilia and Thrombosis, Aarhus University Hospital, Skejby, Denmark
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Benny Sørensen, Haemostasis Research Unit, Centre for Haemostasis and Thrombosis, Guy’s & St Thomas’ NHS Foundation Trust, St Thomas’ Hospital, 1st Floor North Wing, Westminster Bridge Road, London SE1 7EH, UK.
Tel.: +44 20 71882775; fax: +44 20 74013125.
E-mail: benny.sorensen@kcl.ac.uk

Abstract

Summary.  Background: Patients with a history of venous thrombosis occasionally have shortened APTTs when compared with those of healthy references, but the clinical applicability of a shortened APTT is limited. Objectives: The present study aimed to characterize dynamic APTT profiles in patients with previously documented venous thrombosis and hypothesized that the APTT-MaxVel was significantly elevated in patients with a history of venous thrombosis as compared with healthy controls. Methods: We performed a case control study, enrolling a total of 38 patients, 17 males and 21 females, with a verified recent venous thrombotic event, as well as 88 healthy controls. Fifty-three per cent of patients were found to have a biochemical risk factor. A standard APTT was recorded in platelet-poor plasma, and the digital clotting signal was processed using simple algorithms developed to derive dynamic coagulation parameters. Results: Patients had a significantly higher mean APTT-MaxVel (195.5 s−1; SD = 57; 95% CI, 176.8–214.1) as compared with healthy controls (137.3 s−1; SD = 21; 95% CI, 130.7–143.8). Patients also had significantly shorter mean APTTs (26.9 s; SD = 3.2; 95% CI, 25.9–28.0) than healthy controls (28.5 s; SD = 2.8; 95% CI, 27.9–29.0). While only one out of 38 patients (2.6%) had a standard APTT below the lower reference interval, 15 of the 38 patients (38.5%) had an APTT-MaxVel above the upper reference limit. Regression analysis revealed linear correlation between FVIII:C, the level of fibrinogen and APTT-MaxVel (R2 = 0.89, P < 0.05). Conclusions: Simple signal processing of the APTT and the use of dynamic parameters represents a stronger predictive marker for hypercoagulation in patients with verified venous thrombosis than the standard APTT measurement.

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