Reference interval, longitudinal variability and reliability of activated clotting time in healthy dogs using a point-of-care analyser.

Abstract

Activated clotting times (ACTs) are used to screen for coagulopathies and monitor heparin therapy. To determine a reference interval (RI) for ACT in dogs using a point-of-care analyser, to quantify intra-subject within- and between-day variability, to quantify analyser reliability and inter-analyser agreement and to study the influence of a delay in measurement. Forty-two healthy dogs were included. Measurements were performed on fresh venous blood using the i-STAT 1 analyser. The RI was determined using the Robust method. Intra-subject within-day variability and between-day variability were quantified between baseline and 2h (n=8) or 48h (n=10) later. Analyser reliability and inter-analyser agreement were studied by duplicate measurements (n=8) on identical analysers. The influence of measurement delay was studied before and after a delay of one analytical run (n=6). Mean, lower and upper reference limits for ACT were 92.9±9.1, 74.4 and 111.2s, respectively. Coefficients of variation of intra-subject within- and between-day variability were 8.1% and 10.4%, respectively, resulting in a significant between-day measurement difference. Analyser reliability assessed by the intraclass correlation coefficient and coefficient of variation were 0.87% and 3.3%, respectively. Significantly lower ACT values were observed after a measurement delay compared to direct analysis. Our study provides an RI for ACT in healthy dogs using the i-STAT 1 and suggests low intra-subject within- and between-day variability. Analyser reliability and inter-analyser agreement were good; however, analysis delay and between-day differences could significantly influence ACT results.