An antithrombin III assay based on factor Xa inhibition provides a more reliable test to identify congenital antithrombin III deficiency than an assay based on thrombin inhibition.

Abstract

OBJECTIVES:

To determine whether functional antithrombin III (AT-III) levels measured by a factor Xa inhibition (AT-III-Xa) assay identifies AT-III deficient individuals more reliably than functional AT-III levels measured by a thrombin inhibition (AT-III-IIa) assay.

STUDY DESIGN:

Cross-sectional study.

PATIENT POPULATION:

Sixty-seven members of a large family with type 2 AT-III deficiency.

INTERVENTION:

DNA analysis was used as the reference diagnostic standard for AT-III status and subjects were classified as AT-III deficient or non deficient according to these results. Functional AT-III levels were measured in all subjects using: 1) a chromogenic substrate for thrombin and added human thrombin (AT-III-IIa), and 2) a chromogenic substrate for factor Xa and added bovine factor Xa (AT-III-Xa). Functional heparin cofactor II (HC-II) levels were measured using a commercially available kit. The proportions of 125I-alpha-thrombin complexed to AT-III and HC-II were measured by polyacrylamide gel electrophoresis and autoradiography.

RESULTS:

Thirty-one (46%) individuals were classified as AT-III deficient and 36 (54%) as AT-III non deficient. AT-III-Xa assay measured a significantly lower mean AT-III value and a narrower range for individuals classified as AT-III deficient than the AT-III-IIa assay. Using the AT-III-IIa assay, six subjects had borderline AT-III levels compared to none with the AT-III-Xa assay.(ABSTRACT TRUNCATED AT 250 WORDS)

• Authors: C Demers, P Henderson, M A Blajchman, M J Wells, L Mitchell, M Johnston, F A Ofosu, F Fernandez-Rachubinski, M Andrew, J Hirsh
• Journal: Thrombosis and haemostasis (Thromb Haemost) Vol. 69 Issue 3 Pg. 231-5 (Mar 01 1993) ISSN: 0340-6245 [Print] Germany
• PMID: 8470046 (Publication Type: Case Reports, Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Factor Xa Inhibitors
• Heparin Cofactor II
• Antithrombin III
• Prothrombin
• Factor IIa

Topics

• Adolescent
• Adult
• Aged
• Antithrombin III (analysis)
• Antithrombin III Deficiency
• Blood Coagulation Disorders (diagnosis, genetics)
• Child
• Child, Preschool
• Consanguinity
• Evaluation Studies as Topic
• Factor Xa Inhibitors
• Female
• Heparin Cofactor II (analysis)
• Humans
• Male
• Middle Aged
• Prothrombin (antagonists & inhibitors)
• Sensitivity and Specificity