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ItemEvaluation of the analytical performance of a clinical laboratory coagulation analyser for coagulation factor measurement in canine plasma( 2022)Abstract Objective: To evaluate the analytical performance of a clinical laboratory coagulation analyser (Stago Compact Max) for coagulation factor activity measurement in canine plasma. Design: Prospective, observational, analytical study. Methods: Whole blood was collected from 15 privately owned dogs aged between 1 and 8 years old. Dobermans and greyhounds were excluded from sample collection. Five dogs (Pool A) over 25kg had up to 175mL of blood drawn from the jugular vein, and this was processed to citrated, platelet free plasma, and combined to provide a sample pool. Ten dogs (Pool B) over 10kg had 20mL of whole blood drawn from the jugular vein, and this was processed to citrated, platelet free plasma and combined to provide a comparison pool. Complete blood count, biochemistry testing and prothrombin (PT) and activated partial thromboplastin time (aPTT) testing was performed on all dogs prior to blood draw. Samples were excluded if they were visually haemolysed, lipaemic or jaundiced. Pool A was used to assess linearity, within-run and between-run precision of fibrinogen, factor II (FII), factor V (FV), factor VII (FVII), factor VIII (FVIII) and factor X (FX). A modified one stage PT assay utilizing human factor deprived plasmas was performed for FII, FV, FVII and FX. A modified aPTT assay utilizing human factor deprived plasma was performed for FVIII. Fibrinogen was measured via the modified clotting method of Clauss. All coagulation testing was performed as per the manufacturer’s guidelines (Diagnostica Stago). Barbitone buffer was used to perform dilutions on aliquots of Pool A, and 7 dilutions were each tested 20 times on the first day of testing to supply data for within-run precision and linearity, and then tested 5 times further for 4 consecutive days to provide data for between-run precision. The following sample: buffer dilutions were tested: undiluted, 9:1, 7:3, 1:1, 3:7, 1:9, 1:19. For coagulation factor activity testing, time to clot formation was measured and interpolated with a standard curve prepared from Pool B plasma. Fibrinogen was interpolated with the calibration curve provided by the manufacturer. Limit of the blank was assessed by performing each coagulation test 5 times with barbitone buffer only. Results: Results were tabulated and mean, standard deviation and coefficient of variation calculated for each factor, for within-run and between-run precision. Concentration vs measured activity were plotted and line of best fit and linear regression analysis performed. Acceptable linearity was determined as an R squared value >0.95. R squared values were as follows: Fibrinogen 0.99, FII 0.99, FV 0.99, FVII 0.99, FVIII 0.99, FX 0.99. Acceptable coefficient of variation was determined based on manufacturer’s data and factor activity levels of importance. Coefficient of variation was above the acceptable range for FV (between-run precision) at an analyte concentration of 5%, FVII (between-run precision) at analyte concentrations of 50%, 30% and 5% and FX (between-run precision) at an analyte concentration of 5%. Relevance: Investigation of coagulation disorders in dogs is a rapidly growing field in veterinary medicine, and the effects of critical illness on coagulation factor activity are poorly understood. Evaluation of the analytical performance of a clinical laboratory coagulation analyser for coagulation factor activity measurement in dogs is the first step in increasing research and clinical assessment in this area.