The individual systematic difference between CoaguChek and STA-SPA+

Using CoaguChek to measure PT-INR and comparing the results with those from the hospital laboratory, some patients get consistent results while others do not. The extent of this problem is unknown. Our study aimed to quantify the between-subject variation of the systematic PT-INR difference between...

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Bibliographic Details
Published in:Scandinavian journal of clinical and laboratory investigation Vol. 79; no. 3; pp. 143 - 147
Main Authors: Åsberg, Arne, Hegseth, Hilde, Averina, Maria, Løfblad, Lena
Format: Journal Article
Language:English
Published: England Taylor & Francis 03.04.2019
Subjects:
Adolescent
Adult
Aged
Aged, 80 and over
Between-subject variation
Blood Coagulation Tests - methods
Child
Child, Preschool
CoaguChek
Female
Humans
International Normalized Ratio
Male
method comparison
Middle Aged
Point-of-Care Systems
point-of-care testing
Regression Analysis
warfarin
Young Adult
point-of-care testing
Between-subject variation
method comparison
CoaguChek
international normalized ratio
warfarin
ISSN:0036-5513, 1502-7686, 1502-7686
Online Access:Get full text
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Summary:Using CoaguChek to measure PT-INR and comparing the results with those from the hospital laboratory, some patients get consistent results while others do not. The extent of this problem is unknown. Our study aimed to quantify the between-subject variation of the systematic PT-INR difference between CoaguChek and a hospital laboratory method. We used register data with PT-INR results from both CoaguChek and a hospital laboratory method (STA-SPA+) in samples taken simultaneously from 108 patients. After excluding five patients with outlying results, we used mixed-effects models to estimate individual slopes and intercepts to describe the systematic relationship between the two methods for each patient, and calculated the fraction of patients having a systematic difference greater than 0.3 INR units. The included 103 patients had from 3 to 16, median seven data pairs measured over a time span from 15 to 2319, median 234 days. The mean of individual slopes was 1.113, with a standard deviation of 0.137. Corresponding values for the intercept were -0.151 and 0.208, respectively. Adjusted for the average systematic difference, the proportion of patients with a systematic difference greater than 0.3 INR units increased from 15% at a PT-INR level of 2.5 to 50% at a PT-INR level of 4. The systematic difference between CoaguChek and STA-SPA + varies considerably between patients. This precludes using a single, common formula to make the CoaguChek results directly comparable to the results from the hospital laboratory.
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ISSN:0036-5513
1502-7686
1502-7686
DOI:10.1080/00365513.2019.1576097