Effect of Time Interval between Collection, Plasma Separation and Analysis and the Effect of Temperature on the Laboratory Results of Plasma Glucose Estimation

Introduction: In a clinical laboratory, consistency of test results cannot be solely achieved by controlling the accuracy in the analytical phase of glucose estimation alone. Considering the high chances of pre-analytical errors, due consideration has to be given for storage criteria as well.

Aims: Aim is to find out the quantitative alterations and the useful time interval between collection and analysis and the effect of temperature on the laboratory results of plasma glucose.

Study Design: Cross sectional study.

Place and Duration of Study: Study was conducted at Department of Biochemistry, Kasturba Medical College Hospitals, Mangaluru between 2015 and 2016.

Methodology: In this study, 17 apparently healthy volunteers aged 20-30 years were enrolled with their consent. Plasma glucose levels were estimated by glucose oxidase- peroxidase kit method in semi-autoanalyzer at different temperatures and at different time intervals after collection and at room temperature but separating plasma at different time intervals and correlating it with the initial value.

Results: The mean of plasma glucose when estimated immediately after separation of plasma was 78.16 ± 13.28 mg/dL. Only when glucose was estimated within 2 hrs when stored at 2-8° Celsius after plasma separation (71.57 ± 12.64), non- significant difference was noted (p value – 0.696) otherwise as the temperature and time interval for estimation increases, the value of glucose decreases significantly. The effect of delayed separation of plasma showed that as the time of separation increases the value of glucose decreases significantly in the sample.

Conclusion: Most mistakes occur before the samples are analysed, either during sampling or preparation for analysis. Thus, proper storage temperature and time must be considered for plasma glucose estimation, if measurement cannot be done immediately.