Comparison of glucose concentration measured in samples collected with different anticoagulants and analyzed using 2 glucose quantification methods

Sodium fluoride (NaF), K₂-EDTA, and lithium heparin are common anticoagulants used during collection of bovine blood for glucose concentration. Whereas NaF is considered the best anticoagulant for preservation of glucose, other anticoagulants are used because of their ability to simultaneously preserve other metabolites frequently measured in dairy science experiments. To simplify sample collection and reduce the need for multiple tubes, it may be possible to use tubes with anticoagulants other than NaF, provided they yield comparable glucose concentrations. Additionally, blood glucose concentrations are commonly analyzed using a peroxidase and glucose oxidase (PGO) colorimetric assay with a standard plate reader, but the use of a semi-automated chemistry analyzer with a hexokinase (HK) enzymatic reaction method is becoming more common in dairy research because it is also available and easy to use. Thus, the objective of this study was to determine the influence of the use of NaF, dipotassium EDTA (K₂-EDTA), or lithium heparin (Li-Hep) as anticoagulants on glucose quantification, using both the PGO and HK enzymatic reaction methods. Blood samples from 20 fresh cows (7 ± 3 DIM) were collected into NaF, K₂-EDTA, or Li-Hep plasma tubes on a commercial dairy farm (n = 60 samples). All samples were analyzed using both the PGO method, performed on a 96-well plate with a colorimetric microplate reader, and the HK method, conducted on a semi-automated chemistry analyzer. It was observed that in both methods, samples collected into NaF tubes had less glucose quantified compared with samples collected into K₂-EDTA and Li-Hep tubes. Additionally, it was observed that in samples quantified with the HK method, the glucose concentrations were lower than when those samples were quantified with the PGO method. Thus, the K₂-EDTA and Li-Hep anticoagulant could be used for glucose quantification to avoid cumbersome collection of several tubes, but results must be reviewed with caution as concentrations would be higher compared with those quantified with NaF. This observation is also conserved when quantifying glucose using the PGO and HK methods.