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Objectives of study: Presently, the quality of laboratory analysis depends to a great extent on the exposure of specimens during and after sampling. In this study we investigated the influence of different transport and sampling conditions on blood parameters of cattle.
Materials and Methods: Blood was obtained with the Becton Dickinson (BD) Vacutainer® System from 23 cows into serum tubes and tubes containing NaF/Ox. They were centrifuged before transport or transported as whole blood at 20°C or 4°C. Analyses were carried out in intervals over a 48h period. AST, Na, K, glucose, hydroxybutyrate (BHBA) and nonesterified fatty acids (NEFA) were measured. In order to examine open versus closed systems we obtained blood from 30 cows into Sarstedt Monovettes®, BD Vacutainers® and open tubes. Analyses were carried out within 3h after centrifuged transport at 4°C.
Results: AST, Na, K and NEFAs remained stable over a period of 48h in centrifuged samples both at 20°C and 4°C. In whole blood only Na were stable over 48h, whereas AST and K levels increased after 12h and NEFA levels behaved inconstantly beyond 4h. BHBA showed a slight increase after 8h but remained stable on this level in centrifuged samples. In whole blood BHBA varied about +/-17%. Glucose remained stable in centrifuged serum samples as well as separated NaF/Ox plasma but was significant (p<0.001) lower in plasma. Stored as whole blood, glucose values decreased beyond 4h in serum and varied about +/-15% in plasma. The comparison of the different sampling systems showed that the difference between the open and the closed Monovette® was the least. The difference between the Vacutainer® and the closed Monovette® was mostly significant (p=0.05). NEFAs were always significantly lower in Vacutainers® compared to Monovettes®.
Conclusions: A variance analysis showed that centrifugation had an effect to the amount of 34% and chilling during transport amounted to 10% in the mean, indicating that centrifugation before transport is of higher importance than chilling. Additionally, blood samples should be processed as soon as possible. Besides, NaF/Ox tubes are only useful with respect to determination of blood glucose if samples can not be centrifuged immediately. However, glucose values of NaF/Ox plasma were in the mean 0.2 mmol/l lower as serum values. We recommend, reference values should be related to the blood sampling system used.