Assessment of Biological Variation of Hemostatic Parameters in Healthy Dogs Using a Point-Of-Care Viscoelastic Coagulometer.

Abstract

Background: Hemostasis has traditionally been assessed by clotting times; however, point-of-care viscoelastic coagulometers have added to the diagnostic options for assessing hemostasis. Biological variation of diagnostic tests determines whether population- or subject-based reference intervals are used for result interpretation.

Objective: To assess the biological variation of hemostatic parameters in healthy dogs when using a point-of-care viscoelastic coagulometer, VCM Vet.

Materials and methods: Nine healthy dogs. Four VCM Vet tests were simultaneously performed on four different machines immediately after sample collection for each dog. Repeated VCM Vet tests were performed on each dog a total of four times every 28 days. A nested ANOVA was used to assess inter-individual (CVg), intra-individual (CVi), and analytical variation (CVa). Indexes of individuality (IoI) and reference change values (RCV) were calculated.

Results: Two dogs were suspected to have artifactual clot retraction during ten separate tests. These tests were excluded from further analysis. CVg, CVi, CVa, IoI, and RCV for each of the hemostatic parameters were: clotting time (4.4, 11.5, 8.2, 3.2, 39.2%); clot formation time (10.0, 10.8, 8.9, 1.4, 38.7%), alpha (4.5, 4.8, 4.2, 1.4, 17.6%), maximum clot formation (5.3, 6.4, 6.0, 1.7, 24.4%), amplitude at 10 min (6.6, 8.8, 6.6, 1.7, 30.5%), and amplitude at 20 min (6.1, 7.5, 6.1, 1.6, 26.8%).

Conclusions: Intra-individual variation was higher than inter-individual variation for parameters measured with this point-of-care viscoelastic coagulometer. Based on an IOI above > 1.4 for all parameters assessed, population-based reference intervals are appropriate for this point-of-care viscoelastic coagulometer.