RESUMEN
BACKGROUND: Packed cell volume (PCV) is important for assessing a patient's health status. Some blood gas analyzers measure hematocrit, and the agreement with PCV varies among different analyzers. OBJECTIVES: We aimed to determine the agreement between PCV measured by microcentrifugation and hematocrit measured by the Cobas b121 blood gas analyzer in dogs, cats, and horses. METHODS: Whole blood samples for PCV and blood gas analysis were collected in lithium-heparin syringes and analyzed within 10 min of collection. Agreement and association between the PCV and Cobas b121 generated hematocrit were assessed by the Bland-Altman method, Pearson's correlation, Deming regression analysis, and paired t tests. A total allowable error of 10% was used for the analysis. RESULTS: This study included 45 dogs, 45 cats, and 33 horses. The respective mean ± SD (minimum-maximum) of PCVs and hematocrits were: dogs, 34.9 ± 9.9% (9.0-55.0) and 32.5 ± 8.8% (10.4-50.6); cats, 29.0 ± 9.6% (11.0-51.0) and 26.9 ± 9.3% (10.2-50.9); horses, 34.2 ± 6.5% (24.0-47.0) and 34.1 ± 6.0% (22.5-46.1). There were no significant differences between the methods. The bias ± SD was: dogs, -2.4 ± 2.6%; cats, -2.2 ± 2.3%; horses, -0.1 ± 2.4%. Pearson's correlation coefficients were > 0.90 for all species (P < 0.0001). In 60%, 49%, and 85% of the samples for dogs, cats, and horses, respectively, the percentage differences between the methods were within 10%. CONCLUSIONS: The Cobas b121 blood gas analyzer provided accurate estimates of PCVs in horses. However, in dogs and cats, there was a large frequency of unacceptable differences between the methods.