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Original ArticleOpen Access
Accuracy of International Normalized Ratio Determined by Portable Venous-Blood Coagulation Monitor versus a Central Laboratory
Sirithunyanont C 
,
Bhuripanyo K ,
Kangkagate C ,
Winyarat W ,
Srichaya P ,
Wangtip BK
,
Bhuripanyo K ,
Kangkagate C ,
Winyarat W ,
Srichaya P ,
Wangtip BK KIERTIJAI BHURIPANYO, MD*,
WIRANEE WINYARAT,BNS*,
KANOKKWAN WANGTIP,BNS*
Background
: The CoaguChek is a portable monitor unit for measuring the international
normalized ratio (INR). The purpose of the study was to evaluate the accuracy of a portable prothrombin
time (PT) monitor (CoaguChek, Roche Diagnostics, Mannheim, Germany) compared with the labora-
tory method.
Material and Method
: Paired venous blood INRs were performed in 220 consecutive out-
patient tests mainly in anticoagulated (n
=
210) and non-anticoagulated (n
=
10) individuals. Accuracy
was evaluated in 220 tests by parallel assessment of INRs (CoaquChek and laboratory). Accuracy was
determined using statistic regression analysis and clinical agreement (expanded and narrow criteria).
Agreement in dual INR measurement also was evaluated as a function of increasing INR.
Results
: The CoaguChek significantly correlated with the laboratory measurement (r
=
0.89).
The proportion of dual INR measurements that satisfied the clinical relevant expanderl, and narrow
agreement criteria was 90 per cent and 86 per cent respectively. Eighty-two per cent of all dual mea-
surements were within 0.5 INR units. The accuracy of the portable monitor was greatest for INR values
less than 3.0; above this INR level the portable monitor overestimated laboratory INR values.
Conclusions
:The CoaguChek is an accurate alternative to laboratory assessment of INR at
values< 3.0. The authors suggest the use of the monitor in non anticoagulated patients or anticoagu-
lated patients at values less than 3, as most physicians in Thailand prefer lower INR than in Western
countries.
Key word
: Accuracy, Clinical Agreement, Portable INR, Laboratory INR, Warfarin
WIRANEE WINYARAT,BNS*,
KANOKKWAN WANGTIP,BNS*
Background
: The CoaguChek is a portable monitor unit for measuring the international
normalized ratio (INR). The purpose of the study was to evaluate the accuracy of a portable prothrombin
time (PT) monitor (CoaguChek, Roche Diagnostics, Mannheim, Germany) compared with the labora-
tory method.
Material and Method
: Paired venous blood INRs were performed in 220 consecutive out-
patient tests mainly in anticoagulated (n
=
210) and non-anticoagulated (n
=
10) individuals. Accuracy
was evaluated in 220 tests by parallel assessment of INRs (CoaquChek and laboratory). Accuracy was
determined using statistic regression analysis and clinical agreement (expanded and narrow criteria).
Agreement in dual INR measurement also was evaluated as a function of increasing INR.
Results
: The CoaguChek significantly correlated with the laboratory measurement (r
=
0.89).
The proportion of dual INR measurements that satisfied the clinical relevant expanderl, and narrow
agreement criteria was 90 per cent and 86 per cent respectively. Eighty-two per cent of all dual mea-
surements were within 0.5 INR units. The accuracy of the portable monitor was greatest for INR values
less than 3.0; above this INR level the portable monitor overestimated laboratory INR values.
Conclusions
:The CoaguChek is an accurate alternative to laboratory assessment of INR at
values< 3.0. The authors suggest the use of the monitor in non anticoagulated patients or anticoagu-
lated patients at values less than 3, as most physicians in Thailand prefer lower INR than in Western
countries.
Key word
: Accuracy, Clinical Agreement, Portable INR, Laboratory INR, Warfarin
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