This Article  • References  • Full text PDF  • Send to a friend  • Save in My Folder  • Save to citation manager  • Permissions  Citing Articles  • Citation map  • Citing articles on HighWire  • Citing articles on Web of Science (73)  • Contact me when this article is cited  Related Content  • Similar articles in this journal  Social Bookmarking   What's this?

Comparison With a Criterion Standard

Scott S. Kaatz, DO; Richard H. White, MD; James Hill; Edward Mascha, MS; John E. Humphries, MD; Daniel M. Becker, MD

Arch Intern Med. 1995;155(17):1861-1867.

Abstract
Background
Portable instruments that measure the prothrombin time and automatically calculate the international normalized ratio (INR) with the use of a drop of whole blood have simplified the treatment of patients who are receiving warfarin therapy. The accuracy of these portable monitors has never been determined by comparing INR results with a criterion (gold) standard INR determination.

Methods
Duplicate whole-blood INR determinations were made with two commercially available portable INR monitors. Duplicate frozen-plasma samples were measured with four different thromboplastin reagents, each with a different international sensitivity index. The criterion standard INR was determined by using an international reference thromboplastin and the manual tilt-tube technique. Agreement was evaluated by determining how accurately laboratory and monitor INR determinations matched criterion standard values in designating a sample to be within or outside of currently recommended INR target ranges.

Results
Two of the laboratory methods, which used relatively sensitive thromboplastins, showed close agreement with the criterion standard, whereas two laboratory methods that used less sensitive thromboplastin reagents showed poor agreement. Both of the portable monitors fell between these extremes. The two best laboratory methods were significantly better (P<.003) than both monitors, which in turn were better (P<.003) than the remaining two laboratories.

Conclusions
There is large interlaboratory variation in the accuracy of INR determinations. Laboratory methods that used insensitive (high international sensitivity index) thromboplastins performed poorly. Accuracy of monitor measurements appears satisfactory.

(Arch Intern Med. 1995;155:1861-1867)

Author Affiliations
From the Department of Internal Medicine (Dr Kaatz) and Division of Biostatistics (Mr Mascha), Henry Ford Hospital, Detroit, Mich; Department of Medicine, University of California, Davis, Sacramento (Dr White); Boehringer Mannheim Corp, Indianapolis, Ind (Mr Hill); and Department of Medicine, University of Virginia School of Medicine, Charlottesville (Drs Humphries and Becker).

CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter     What's this?

THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES

Delivery of Optimized Anticoagulant Therapy: Consensus Statement from the Anticoagulation Forum
Garcia et al.
The Annals of Pharmacotherapy 2008;42:979-988.
ABSTRACT | FULL TEXT  

Pharmacology and Management of the Vitamin K Antagonists: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)
Ansell et al.
Chest 2008;133:160S-198S.
ABSTRACT | FULL TEXT  

Accuracy and clinical utility of the CoaguChek XS portable international normalised ratio monitor in a pilot study of warfarin home-monitoring
Bereznicki et al.
J. Clin. Pathol. 2007;60:311-314.
ABSTRACT | FULL TEXT  

Validity of Criteria Used to Evaluate Fingerstick Devices That Assess International Normalized Ratio
Shermock et al.
Med Decis Making 2006;26:239-246.
ABSTRACT  

Anticoagulation Monitoring Part 1: Warfarin and Parenteral Direct Thrombin Inhibitors
Spinler et al.
The Annals of Pharmacotherapy 2005;39:1049-1055.
ABSTRACT | FULL TEXT  

The Pharmacology and Management of the Vitamin K Antagonists: The Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy
Ansell et al.
Chest 2004;126:204S-233S.
ABSTRACT | FULL TEXT  

Reliability of international normalised ratios from two point of care test systems: comparison with conventional methods
Poller et al.
BMJ 2003;327:30.
ABSTRACT | FULL TEXT  

American Heart Association/American College of Cardiology Foundation guide to warfarin therapy
Hirsh et al.
J Am Coll Cardiol 2003;41:1633-1652.
FULL TEXT  

American Heart Association/American College of Cardiology Foundation Guide to Warfarin Therapy
Hirsh et al.
Circulation 2003;107:1692-1711.
FULL TEXT  

Thrombophilia: What's a Practitioner to Do?
Macik et al.
ASH Education Book 2001;2001:322-338.
ABSTRACT | FULL TEXT  

Managing Oral Anticoagulant Therapy
Ansell et al.
Chest 2001;119 :22S-38S.
FULL TEXT  

Preventing Stroke in Patients With Atrial Fibrillation
Ezekowitz and Levine
JAMA 1999;281:1830-1835.
ABSTRACT | FULL TEXT  

Empowering Patients to Monitor and Manage Oral Anticoagulation Therapy
Ansell
JAMA 1999;281:182-183.
FULL TEXT