Hematocrit estimates comparing centrifugation to a point-of-care method in beef cattle living at high altitude.

BACKGROUND The hematocrit (Hct) or packed cell volume (PCV) reflects the blood volume occupied by red blood cells. The development of point-of-care (PoC) instruments can accelerate the ease of measuring Hct/PCV compared with traditional capillary centrifugation (TCC) methods. However, no studies have compared Hct/PCV levels in cattle at high elevation with other measurement methods. OBJECTIVES In this study, we aimed to compare methods to estimate Hcts/PCVs of rangeland cattle at high elevation. We specifically wanted to determine if Hct/PCV levels measured with a commercial PoC instrument (i-Stat with CHEM8+ cartridges [PoCi ]) were comparable to Hct/PCV levels measured with traditional laboratory methods. METHODS We assessed the Hct/PCV of 94 mature beef cattle (black Angus; Bos taurus) at ~2195 m above sea level using paired analyses of the PoCi and TCC methods from each animal. We used paired samples t-tests to compare mean Hct/PCVs. Correlation analyses relative to the line of identity and Passing-Bablok regression were used to assess systematic and proportional differences, respectively, and Bland-Altman plots were used to assess agreement between the two methods. RESULTS The PoCi estimated a Hct of 28.2% ± 0.7% (SE), which was lower than the TCC estimated PCV of 39.2% ± 0.5%. The Bland-Altman plot revealed poor agreement between the two methods in addition to a -11% bias for the PoCi . The Passing-Bablok regression revealed both systematic and proportional bias between the two methods. CONCLUSIONS Point-of-care blood instruments were not comparable to TCC methods for quantifying Hct/PCVs of cattle living at high elevations.