A Comprehensive Stability Study of Glucose Concentrations Measured in Sodium Fluoride, Heparin and Serum Separator Tubes: A Cross-sectional Study

Introduction: Sodium fluoride mixed vacutainers were once viewed as the gold standard tubes for glucose analysis. However, their ineffectiveness in inhibiting glycolysis, especially in the first one to four hours has been reported in several studies. The accurate blood glucose estimation is crucial for the diagnosis and management of diabetes mellitus. Aim: To find out a cost effective and feasible alternative blood collection vacutainer for the estimation of accurate blood glucose. Materials and Methods: A cross-sectional study was conducted at the Blood Collection Centre of HAH Centenary Hospital, New Delhi, India, from December 2019 to July 2020. A blood sample was collected from 155 subjects in each-sodium fluoride [Na2EDTA], heparin [sodium heparin] and Serum Separator Tube (SST). To find out the glucose reduction during blood coagulation in SST tubes, the glucose levels (n=25) of sodium fluoride (plasma) at 0 hr and 30 mins after coagulation in SST tubes were compared. The remaining study subjects (n=130) were categorised into two groups (65 subjects in each group) and assessed for the reduction of glucose at 4°C and 25°C. Further, the reduction of glucose was also studied in both the groups as per glucose concentrations <100 mg/dL (n=25), 100-200 mg/dL (n=25) and >200 mg/dL (n=15) in each group. Results: The inter assay coefficient of variation of quality control samples of glucose (n=61) was 3.0%. The highest percentage of glucose reduction was found in the green vacutainers (p<0.05) at 4°C and 25°C storage temperatures. There was no significant reduction of glucose level in SST vacutainers at 4°C up to 96 hrs of analysis (p>0.05) and the result was comparable to grey vacutainers. Further, there was no haemolysis in the SST vacutainers up to 96 hrs of analysis, however, green and grey vacutainers showed enormous haemolysis. Conclusion: The glucose analysis in SST vacutainers can reduce the loss of sample, cost of analysis, and interferences in the analysis due to haemolysis. The study strongly suggests that all the analytical laboratories should do glucose analysis in SST vacutainers.