A Study to Compare the Plasma Glucose Levels Obtained in Sodium Fluoride and Citrate Buffer Tubes at a Tertiary Care Hospital in Punjab

Objectives: Recent guidelines for estimation of glucose recommend the use of citrate buffer tubes to inhibit glycolysis if the sample cannot be cooled immediately and separated within 30 min. These tubes are currently not available in India. We prepared the citrate tubes and compared the glucose results obtained with sodium fluoride tubes.

Methods: Random blood samples of 44 apparently healthy volunteers were collected in three pairs of citrate buffer and sodium fluoride tubes during September to October 2013. They were labeled as 0 h, 1 h and 2 h samples indicating a delay in centrifugation to separate plasma. Glucose was analyzed on the fully auto analyzer in duplicates using glucose oxidase-peroxidase method.

Results: The mean glucose concentrations at 0 h in citrate tubes were 105.8 ± 19.5 mg/dl compared to 99.6 ± 18.3 mg/dl in sodium fluoride tube. There was statistically significant difference in the glucose levels measured in plasma separated from citrate buffer tube and sodium fluoride tube at 0 h, 1 h, and 2 h. The difference between citrate and sodium fluoride tube results ranged from 6.1 mg/dl at 0 h to 7.4 mg/dl at 2 h. Glucose levels decreased significantly at 2 h in both citrate and sodium fluoride tubes.

Conclusion: There is a significant decrease in glucose levels in sodium fluoride tubes even with immediate separation of plasma. There is urgent need to standardize the preanalytical conditions for glucose estimation so that effective inhibition of glycolysis can be done.