Activated protein C resistance assay performance: improvement by sample dilution with factor V-deficient plasma.

Abstract

OBJECTIVE:

To evaluate a modification of a commercially available reagent kit (COATEST APC Resistance Kit) for functional activated protein C (APC) resistance testing, and to determine the ability of the modified assay to demonstrate APC resistance in patients receiving warfarin.

DESIGN:

Functional APC resistance testing was performed using both the first-generation COATEST APC Resistance Kit and a modified, or second-generation, version of the COATEST assay that uses predilution of the patient sample with factor V-deficient plasma. Factor V genotyping for APC resistance (FV R506Q) was performed using a well-characterized polymerase chain reaction-restriction fragment length polymorphism method.

SETTING:

University medical center.

PATIENTS:

Seventy-three individuals referred for hypercoagulability testing who were not receiving warfarin therapy and 29 patients with a history of venous thrombosis who were receiving warfarin therapy.

MAIN OUTCOME MEASURE:

Sensitivity and specificity as determined by comparing functional APC resistance to the FV R506Q genotype.

RESULTS:

In 73 patients referred for hypercoagulability testing, but not receiving warfarin therapy, a sensitivity of 0.86 and a specificity of 0.75 were obtained with the first-generation COATEST assay. In contrast, a sensitivity and specificity of 1.0 were obtained when the second-generation COATEST assay was employed. In 29 patients receiving warfarin, the first-generation assay exhibited a sensitivity and specificity of 0.88 and 0.95, respectively, whereas the sensitivity and specificity for the second-generation assay was 1.0.

CONCLUSIONS:

Predilution of patient plasma with factor V-deficient plasma results in improved sensitivity and specificity of the COATEST APC Resistance Kit, thus offering a simple modification to enhance APC resistance determination in the routine clinical laboratory setting.

• Authors: F J Strobl, S Hoffman, S Huber, E C Williams, K V Voelkerding
• Journal: Archives of pathology & laboratory medicine (Arch Pathol Lab Med) Vol. 122 Issue 5 Pg. 430-3 (May 1998) ISSN: 0003-9985 [Print] United States
• PMID: 9593344 (Publication Type: Journal Article)

Chemical References

• Protein C
• Reagent Kits, Diagnostic
• Warfarin

Topics

• Blood Coagulation Disorders (diagnosis)
• Blood Coagulation Tests (methods)
• Evaluation Studies as Topic
• Factor V Deficiency (blood, drug therapy)
• Humans
• Partial Thromboplastin Time
• Protein C (pharmacology)
• Reagent Kits, Diagnostic
• Sensitivity and Specificity
• Warfarin (therapeutic use)