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Effect of sample handling and storage time on the stability of total CO 2 in equine plasma
Author(s) -
Tinkler S. H.,
Couëtil L. L.,
Constable P. D.
Publication year - 2012
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/j.2042-3306.2012.00610.x
Subject(s) - vacutainer , centrifugation , chemistry , chromatography , blood collection , zoology , medicine , biology , emergency medicine
Summary Reasons for performing study: The stability of total CO 2 concentration (ctCO 2 ) in plasma is influenced by storage temperature and handling during sample processing. Conflicting information exists regarding the stability of ctCO 2 in equine plasma over time, and the effect of centrifugation on the measured value for plasma ctCO 2 is unclear. Objectives: To determine plasma ctCO 2 stability over 5 days when equine blood is collected into Vacutainer tubes, centrifuged within 30 min of collection, and stored at 4°C; and to determine whether a delay in centrifugation increases the rate at which plasma ctCO 2 decreases over time. Methods: Blood was collected from 6 adult horses into 3 ml plastic Vacutainer tubes and randomly assigned to be centrifuged immediately, or after, storage. Plasma ctCO 2 was measured in triplicate at 0, 24, 48, 72 and 96 h after collection using a NOVA‐4 analyser. Data were analysed using multivariable linear regression, with P<0.05 being defined as significant. Results: Plasma ctCO 2 decreased linearly over time during storage at 4°C. The measured value for ctCO 2 decreased at a faster rate (‐0.28 mmol/l/day; P<0.0001) when centrifugation was delayed, compared with immediate centrifugation (‐0.10 mmol/l/day). There was a significant effect of sequence of sample analysis on the ctCO 2 value when measured in triplicate: the second and third measurements were 0.31 and 0.41 mmol/l lower than the first measurement, respectively. Conclusions: Blood samples collected from horses into Vacutainer tubes should be centrifuged immediately after collection and analysed as soon as possible to ensure accurate values for plasma ctCO 2 . Potential relevance: Failure to centrifuge, or excessive delay in measuring ctCO 2 after centrifugation, produces values significantly lower than the true value.