A study on the assessment of stability of glucose concentrations in serum separator gel tubes

Introduction: Increasing diabetic burden in India has shifted our health care focus towards its prevention and management of diabetes mellitus. Often multiple investigations are requested by the physicians to assess diabetic status. Conventionally fluoride tubes (glycolytic inhibitor) have been used for glucose analysis in clinical laboratories. Preservatives used here make it unsuitable to measure other key clinical chemistry analytes, for which serum separator gel tubes(SST) are being employed. On centrifugation of SST tubes, a thick gel barrier is formed separating the serum from the cells. This gel barrier prevents utilization of glucose by the cells, hence researchers have considered using it for glucose measurement. This study has been done to assess the integrity of serum samples obtained from SST tubes for analysis of glucose. Materials and Methods: A single centre cross-sectional study was done, with 140 paired samples collected in fluoride and SST tubes from patients attending Sri Ramachandra Laboratory Services. Samples were analyzed by glucose oxidase-peroxidase method in Siemens ADVIA 1800 Clinical Chemistry at 1 hr, 6 hrs and 24 hrs of sample collection. Results:Statistical analysis showed no significant change in glucose concentrations measured in fluoride against serum samples. Paired t-test results showed no statistical significance between the tubes, irrespective of time. Bland Altman plot analysis revealed that serum values were not significantly different from fluoride samples throughout the study period. Intraclass correlation (ICC) showed correlation of 0.999 between serum and plasma at 1 hr, 6 hrs and 24 hrs from time of collection. Conclusions: Serum from SST tubes can be used to measure blood glucose instead of standard accepted fluoride plasma samples.