Abstract:
Background: The primary test in the diagnosis and management of diabetes mellitus is the
plasma glucose concentration. Venous blood is collected into tubes that contain
antiglycolytic agents to prevent in vitro glycolysis. However, a complete inhibition of in
vitro glycolysis is a major challenge in current laboratory practice. In addition to overfilling
and under filling of tubes, samples are rarely analyzed within the recommended time period
of one hour from collection.
Objectives: To determine the effect of sample volume variation and time delay in the
analysis of plasma glucose results in healthy adults.
Methodology: A total of 30 individuals aged between 20-25 years were selected for the
study. A 6.5 mL of blood sample was taken from each participant and added into three
fluoride oxalate collection tubes in volumes of 1.0 mL, 2.0 mL and 3.0 mL. Samples were
centrifuged and plasma glucose concentration measured at 1 hour, 3 hours and 5 hours after
the sample collection using glucose oxidase method. Samples were kept at room temperature
until analysis.
Results and conclusions: There is a statistically significant difference in glucose
concentration in 1.0 mL, 2.0 mL and 3.0 mL volumes of samples analyzed after 5 hours of
collection with the baseline control; 2.0 mL sample analyzed after 1 hour of collection (p<
0.05). There is no significant difference in plasma glucose results between different sample
volumes (p>0.05) at a specific time point. At constant sample volumes, there is a significant
difference between results after 1 and 5 hours of collection in 2.0 mL and 3.0 mL volumes
and between 3 and 5 hours in 3.0 mL of samples (p<0.05). The sample volume variation in
2.0 mL fluoride oxalate tube from 1.0 mL to 3.0 mL does not significantly affect the plasma
glucose results. However even in the presence of a glycolytic inhibitor the plasma glucose
concentration decreases upon delaying the analysis after one hour of sample collection.
