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Pare A, Kippen L, Wagg C, Longmore M, Boysen S. Comparison of four different hematocrit assays and the effect of albumin on their measurements. Front Vet Sci 2022; 9:937328. [PMID: 36090165 PMCID: PMC9449412 DOI: 10.3389/fvets.2022.937328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 07/27/2022] [Indexed: 11/13/2022] Open
Abstract
Clinical decisions are influenced by hematocrit values. Centrifugation (reference standard), conductivity, optical and impedance methods are often used interchangeably to measure hematocrit. The effects of albumin, which are known to affect conductivity methods, have not been evaluated for limits of agreement (LOA) between hematocrit assays in small animals. Canine venous blood was collected from 74 clinical cases and measured by centrifugation (n = 72), conductivity (n = 73), impedance (n = 24) and optical (n = 50) methods. Bland-Altman analysis determined bias (± SD) and 95% LOA between methods. There was a statistically significant difference between centrifugation hematocrit values and values obtained via conductivity (p < 0.0001), optical (p < 0.0001), and impedance (p = 0.0082) methods. The conductivity method underestimated hematocrit by 2.1 ± 2.9% (95% LOA −3.54 to 7.88), the optical method by 3.1 ± 3.6% (95% LOA −4.0 to 10.2), and the impedance method by 2.3 ± 3.7% (95% LOA −5 to 9.6) when compared to centrifuged hematocrit values. The hematocrit difference between conductivity and centrifugation methods was statistically different for low (4%, 0–5%), within reference limits (3%, −5 to 8%), and high (2%, −2 to 5%) albumin values, respectively (p = 0.02), with post-hoc analysis demonstrating that the difference occurred between the low and high albumin groups. This study confirms that albumin values outside reference limits can affect the conductivity method and that hematocrit values obtained via conductivity, optical and impedance methods underestimate values obtained via centrifugation. Therefore, the hematocrit methods cannot be used interchangeably. The wide limits of agreement also demonstrates that care must be taken when making clinical decisions with different hematocrit methodologies.
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Affiliation(s)
- Amelie Pare
- Department of Internal Medicine, Western Veterinary Specialist & Emergency Centre–VCA, Calgary, AB, Canada
- *Correspondence: Amelie Pare
| | - Laura Kippen
- Department of Emergency Care, Central Victoria Veterinary Hospital–VCA, Victoria, BC, Canada
| | - Catherine Wagg
- Department of Veterinary Clinical and Diagnostic Sciences, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
| | - Matt Longmore
- Department of Emergency Care, Western Veterinary Specialist & Emergency Centre–VCA, Calgary, AB, Canada
| | - Soren Boysen
- Department of Veterinary Clinical and Diagnostic Sciences, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
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