Continuation of glycolysis in erythrocytes after blood collection may cause an artifactual in vitro increase of methylglyoxal, and consequently of its metabolite D-lactate. Sodium fluoride (NaF) inhibits enolase in the glycolysis pathway. Our hypotheses were that equine blood collected in NaF tubes would result in both valid and lower D-lactate values when compared to serum tubes, and that D-lactate concentrations would be stable up to 6 months at -80°C.
Blood was collected in both serum and NaF tubes from 23 horses and kept on ice until centrifugation for separation of serum or plasma. Samples were frozen at -80°C until analysis (after 1, 2 and 6 months) with a previously validated commercial assay (D-Lactate Colorimetric Assay Kit, BioVision, Inc., Milpitas, CA, USA).
D-lactate values measured from blood collected in serum tubes had a mean (± SD) concentration of 0.26mmol/L (0.09), 0.27mmol/L (0.09) and 0.17mmol/L (0.07) after 1, 2 and 6 months, respectively. From the NaF tubes, the mean D-lactate concentrations were 0.05mmol/L (0.01), 0.06mmol/L (0.01) and 0.03mmol/L (0.01) after 1, 2 and 6 months, respectively. D-lactate was significantly different (P < 0.0001) between serum and NaF samples, and when comparing 6 months to 1 and 2 months within the NaF tube type (P < 0.0001).
Use of NaF tubes is recommended for equine blood collection for determination of D-lactate concentration, as use of serum tubes results in inflated and inaccurate values. Furthermore, longer-term storage (>2 months at -80⁰C) appears to result in sample degradation and should be interpreted with caution.
Large Animal Internal Medicine Resident, MSc candidate
Western College of Veterinary Medicine, University of Saskatchewan
2016/19 Large Animal Internal Medicine Residency, Western College of Veterinary Medicine (University of Saskatchewan)
2016/19 MSc in Large Animal Clinical Sciences, Western College of Veterinary Medicine (University of Saskatchewan)
2015/16 Equine Internship, Brazos Valley Equine Hospital, Navasota, Texas
2014/15 Equine Internship, Sycamore Lodge Equine Hospital, The Curragh, Ireland
2013 Equine Theriogenology Internship, Standardbred breeding farm, Italy
2012 DVM University of Turin, Italy
Thursday, June 14
2:00 PM – 2:15 PM
Friday, June 15
1:30 PM – 1:45 PM
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