Haemoglobin concentration measurement agreement obtained from three different devices in anaesthetised horses

Accurate measurement of haemoglobin concentration is crucial for monitoring the oxygen-carrying capacity in anaesthetised horses. This prospective study aimed to determine the agreement in haemoglobin concentration in anaesthetised horses using the SpHb pulse co-oximeter, an Epoc® blood gas analyser, and values derived from packed cell volume (PCV), which served as the reference method in this study. The study included 34 horses undergoing elective surgeries. Blood samples were collected from each horse and divided for analysis using the microhaematocrit method to estimate haemoglobin concentration ([Hb]PCV_est) and the Epoc®. Haemoglobin concentrations were compared to SpHb readings using Lin's concordance correlation coefficient (CCC) and Bland-Altman analysis, with a predefined acceptable clinical limit of agreement set at a 7 % variance from the reference. The mean [Hb]PCV_est was 14.6 ± 1.8 g/dL, the Epoc® [Hb] was 11.0 ± 1.8 g/dL, and the SpHb® [Hb] was 9.6 ± 1.5 g/dL. Analysis revealed poor agreement between the SpHb and Epoc® devices compared to [Hb]PCV_est. Both SpHb and Epoc® methods underestimated haemoglobin concentrations by an average of 4.96 g/dL and 3.6 g/dL, respectively. Lin's CCC indicated weak concordance (0.08 for SpHb and 0.14 for Epoc®). Bland-Altman analysis demonstrated significant biases, exceeding the acceptable 7 % threshold, with wide limits of agreement. In conclusion, both the SpHb pulse co-oximeter and the Epoc® showed poor agreement with the [Hb]PCV_est method, underestimating haemoglobin levels in anaesthetised horses. Further research with larger sample sizes and species-specific device calibration is necessary to establish the true accuracy and clinical utility of the SpHb Radical-7® device in horses.