Evaluation of a new PT-INR monitoring system in patients with the antiphospholipid syndrome.
BACKGROUND
Patients on anticoagulant therapy with vitamin K antagonists (VKA) need frequent INR monitoring. Reliability of point-of-care (POC) devices for measuring INR needs rigorous evaluation, particularly in patient with the antiphospholipid syndrome (APS). The aim of this study was to evaluate the accuracy of the ProTime InRhythm(™) System (here called device) for INR measurement in patients with APS on VKA.


METHODS
We compared the device INR vs. the laboratory INR measurement for blood samples from 29 APS-positive and 31 APS-negative patients consecutively enrolled. APS was confirmed by positive serological and/or phospholipid-dependent coagulation tests. Chromogenic factor X assay was used to evaluate anticoagulation. Bland-Altman difference plot for paired INR (POC vs. laboratory) was used to evaluate agreement between the device and the laboratory. The device INR relationship with factor X chromogenic assay was evaluated by orthogonal regression analysis.


RESULTS
Overall, 97% of the device INR measurements were similar to laboratory INR values with an absolute difference less than 0.4 units. Correlation coefficient for the device INR vs. factor X was -0.69 (P < 0.0001, CI 95% -0.80 to -0.52).


CONCLUSIONS
The ProTime InRhythm System(™) is an accurate point-of-care device for measuring INR also in patients with and without APS.
Angelo Bianchi Bonomi Hemophilia and Thrombosis Centre, Department of Clinical Sciences and Community Health, Università degli Studi di Milano, Milan, Italy. simon.braham@gmail.com.|Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy. simon.braham@gmail.com.
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Braham
Angelo Bianchi Bonomi Hemophilia and Thrombosis Centre, Department of Clinical Sciences and Community Health, Università degli Studi di Milano, Milan, Italy.|Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.|Laboratory of Clinical Chemistry and Microbiology, Milan, Italy.
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Novembrino
Angelo Bianchi Bonomi Hemophilia and Thrombosis Centre, Department of Clinical Sciences and Community Health, Università degli Studi di Milano, Milan, Italy.|Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
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Moia
Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.|Laboratory of Clinical Chemistry and Microbiology, Milan, Italy.
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Torresani
Angelo Bianchi Bonomi Hemophilia and Thrombosis Centre, Department of Clinical Sciences and Community Health, Università degli Studi di Milano, Milan, Italy.|Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
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Tripodi
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016736:Antiphospholipid Syndrome / Q000097:blood* / Q000188:drug therapy; D005260:Female; D006801:Humans; D019934:International Normalized Ratio / Q000295:instrumentation* / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019095:Point-of-Care Systems
INR; Point-of-care; anticoagulation; antiphospholipid antibodies; factor X