Concentration of dipotassium ethylenediaminetetraacetic acid but not lithium heparin affects total protein determination in equine synovial fluid.

This research investigates the impact of different concentrations of two anticoagulants, dipotassium EDTA and lithium heparin, on total protein determination in equine synovial fluid using a hand-held refractometer. It revealed that high concentrations of dipotassium EDTA, but not lithium heparin, can overestimate total protein levels.

Overview of the Research

• The refractometric determination of total protein (TP) present in a horse’s synovial fluid (SF) is essential for diagnosing and monitoring synovial sepsis, a severe joint infection. However, certain anticoagulants can disrupt the refractometric determination, leading to inaccurate results.
• To gather greater insight into this phenomenon, the researchers considered two common anticoagulants: dipotassium EDTA (KEDTA) and lithium heparin (LH). They designed a cross-sectional observational study to evaluate the effect of four different concentrations of these anticoagulants on refractometric TP determination in equine SF.

Conducting the Research

• They collected 30 SF samples from 22 horses with a range of synovial conditions. These samples were divided into smaller amounts called aliquots, which were then placed in tubes containing varying concentrations of KEDTA or LH.
• Following this, TP determination was carried out on these aliquots, both with and without the added anticoagulants. For this refractometric TP determination, they utilised a hand-held refractometer and cross-verified results using the Biuret method, the gold standard technique for protein measurement.

Research Findings

• The results suggested an overestimation of TP when SF samples contained KEDTA concentrations ten times higher than the recommended amount. Conversely, lower concentrations of KEDTA and the entire range of tested LH concentrations did not alter TP determinations, indicating these levels were not problematic for accurate TP measurement.
• However, they noted that the research was limited by the fact that the majority of the samples came from larger synovial structures, which could potentially skew the results.

Conclusion

• To prevent inaccurate TP measurement in cases where the SF volume is not sufficient to fill a KEDTA collection tube, the researchers suggested the use of LH-containing collection tubes as an appropriate alternative.
• Thus, this study showcases the necessity to consider anticoagulant levels in TP measurement of equine SF to avoid misdiagnosis or incorrect monitoring of synovial sepsis in horses.