Comparison of STA‐NeoPTimal (Stago) and STA‐Neoplastine CI Plus (Stago) thromboplastin reagents using a STA Satellite Max analyzer to measure prothrombin times in dogs

Background Different thromboplastins are available to measure prothrombin time (PT). Stago coagulation analyzers and reagents are currently used in veterinary laboratories and enable PT measurements to explore the coagulation cascade (extrinsic pathway). Objectives The main objective was to compare PT measurements obtained with the STA‐NeoPTimal reagent with the commonly used STA‐Neoplastine CI Plus reagent. The secondary objective was to compare the PT ratio with the international normalized ratio (INR) calculated from our derived clotting times. Methods Analytical performance was evaluated with intra‐assay and inter‐assay precision. Seventy‐two individual canine plasma samples were collected. Each sample was tested with both thromboplastins, using an STA Satellite Max analyzer. The PT, PT ratio, and INR values obtained with the two reagents were compared using Passing‐Bablok regression for correlations and Bland‐Altman plots for method agreements. Results The analytical performance of STA‐NeoPTimal reagent was acceptable. Compared with the STA‐Neoplastine CI Plus reagent, the STA‐NeoPTimal reagent showed a positive proportional bias for PT values. Narrow range analyses showed good agreement for normal PT values (less than 9.5 seconds, internal reference cutoff with STA‐Neoplastine CI Plus), and clinical concordance was achieved. When PT was prolonged (more than 9.5 seconds), PT increases were more marked with the STA‐NeoPTimal reagent. Agreement was good for INR values across the whole range of PT results. Conclusion STA‐NeoPTimal can be reliably implemented in veterinary laboratories for canine PT measurements, as agreement between the PT results measured with the two reagents was clinically acceptable.