Reliability of Point-of-care INR Measurements in Patients With Antiphospholipid-antibody Syndrome Treated With Warfarin

INR Determined by Plasma-based Methods Versus Newer Point-of-care Instruments in Patients With Antiphospholipid-antibody Syndrome Treated With Anticoagulants

The antiphospholipid-antibody syndrome (APLA), which includes lupus anticoagulant, anticardiolipin, and anti-beta-2-glycoproteinI antibodies, is a thrombophilic disorder associated with arterial thrombosis, venous thrombosis or both. Patients diagnosed with APLA have a higher risk of recurrent thrombosis than do patients without known antibodies. Currently, warfarin is considered the anticoagulant of choice for prophylactic antithrombotic treatment for APLA patients after their first episode of thrombosis. In some patients with APLA who are treated with warfarin, the INR values determined on plasma are unreliable due to an influence of the APLA on the INR. In these individuals, alternative monitoring methods, such as factor II activity, chromogenic factor X activity or prothrombin-proconvertin time should be used to assess adequate anticoagulation. These tests are expensive and not widely available to some clinicians. Point-of-care (POC) instruments, on the other hand, are readily accessible to clinicians. Previous research has shown that INR values from 3 older point-of-care (POC) instruments are unreliable in 1/3 of APLA patients (CoaguChekTM, ProTimeTM, INRatioTM). However, there are now newer versions of these POC instruments available (CoaguChek XSTM, an investigational ProTime device, and a newer INRatioTM device) and it is unknown if these newer POC instruments are reliable in patients with APLA. The purpose of this study is to determine whether newer POC instruments are reliable in patients with APLA.

Study Overview

• Status: Completed
• Conditions: Antiphospholipid Syndrome
• Intervention / Treatment: Device: INR by point-of-care instruments and venopuncture

• Study Type: Observational
• Enrollment (Actual): 63

Contacts and Locations

Study Locations

• United States
  • North Carolina
    • Chapel Hill, North Carolina, United States, 27514
      • University of North Carolina at Chapel Hill

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

APLA patients will be identified through the UNC Thrombophilia Program database. Control patients will be recruited at UNC Anticoagulation Clinic visits.

Description

APLA Inclusion Criteria:

• Prolongation of a phospholipid-dependent screening assay, 2) lack of correction of a prolonged screening assay after a 1:1 mix with pooled normal plasma, and 3) correction of a prolonged screening assay by the addition of excess phospholipid. Two positive lupus anticoagulant confirmations at least 3 months apart will be required.
• Diagnosis of anticardiolipin antibodies defined as elevated levels of ACA-IgG (>30) and/or ACA-IgM (>15) on two separate occasions at least 3 months apart.
• Stable warfarin therapy, defined as the maintenance of a warfarin dose for a minimal of 2 weeks regardless of INR.

APLA Exclusion Criteria:

• Patients whose warfarin dose has changed within the past 2 weeks.

Control Inclusion Criteria:

• No evidence of either a positive LA or ACA diagnosis by confirmation of negative laboratory values and/or documentation of no clinical signs and symptoms concurrent with these conditions.
• Stable warfarin therapy, defined as the maintenance of a warfarin dose for a minimal of 2 weeks regardless of INR.

Control Exclusion Criteria:

• Patients whose warfarin dose has changed within the past 2 weeks.

Study Plan

How is the study designed?

Design Details

• Observational Models: Case-Control
• Time Perspectives: Prospective

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
APLA; Patients with antiphospholipid antibody syndrome.	Device: INR by point-of-care instruments and venopuncture; Three fingersticks will be performed and from each one drop of capillary or venous whole blood collected from a fingerstick performed by the primary investigator to measure PT/INR using the CoaguChekXSTM (10 microliters), ProTimeTM (27 microliters), the investigational ProTime, and INRatioTM 15 microliters) point-of-care instruments and one i.v. blood draw (20 mL of blood) will be performed by a phlebotomist.
Control; Patients on warfarin therapy but without antiphosphilipid antibody syndrome.	Device: INR by point-of-care instruments and venopuncture; Three fingersticks will be performed and from each one drop of capillary or venous whole blood collected from a fingerstick performed by the primary investigator to measure PT/INR using the CoaguChekXSTM (10 microliters), ProTimeTM (27 microliters), the investigational ProTime, and INRatioTM 15 microliters) point-of-care instruments and one i.v. blood draw (20 mL of blood) will be performed by a phlebotomist.

Collaborators and Investigators

• Sponsor: University of North Carolina, Chapel Hill
• Collaborators: International Technidyne Corporation
• Investigators: Principal Investigator: Lauren B McKnight, PharmD, University of North Carolina, Chapel Hill

Study record dates

Study Major Dates

• Study Start: March 1, 2009
• Primary Completion (Actual): May 1, 2009
• Study Completion (Actual): May 1, 2009

Study Registration Dates

• First Submitted: April 6, 2009
• First Submitted That Met QC Criteria: April 6, 2009
• First Posted (Estimate): April 8, 2009

Study Record Updates

• Last Update Posted (Estimate): October 15, 2012
• Last Update Submitted That Met QC Criteria: October 12, 2012
• Last Verified: October 1, 2012

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Pathologic Processes; Immune System Diseases; Autoimmune Diseases; Disease; Syndrome; Antiphospholipid Syndrome
• Other Study ID Numbers: POC Comparison 08-1883