Plasma glucose measurement in diabetes: impact and implications of variations in sample collection procedures with a focus on the first hour after sample collection.
BACKGROUND
Previous studies of participants with plasma glucose concentrations at or near the glucose reference range demonstrate glucose loss following delayed separation and extraction of plasma from the cellular components of blood, of ≤7% per hour. We aimed to assess pre-analytical glucose loss in diabetic subjects, focusing on the first hour after sample collection.


METHODS
Venous blood was collected from diabetes clinic attendees, into a series of lithium heparin PST™ (plasma separator tube) and fluoride oxalate Vacutainers™. Baseline (reference) plasma glucose measurements were undertaken on samples prepared under refrigerated conditions. The remaining samples underwent a series of controlled pre-analytical delays in sample preparation, at room temperature. Plasma glucose was measured using the hexokinase method.


RESULTS
Median baseline glucose (mmol/L) for the 62 participants was 10.6 (range 3.4-31.1). Using lithium heparin PST™ tubes, mean glucose loss (95% CI) was 0.16 (0.09-0.23) after 30 min delay in plasma preparation and 0.28 (0.21-0.34) after 60 min delay. Glucose loss was independent of both baseline glucose and also individual cellular count. Fluoride failed to inhibit glucose loss within the first hour after sample collection. Immediate plasma centrifugation of PST™ tubes, followed by delayed plasma extraction (median delay 92 min), produced a mean glucose loss of 0.02 mmol/L (-0.05-0.09).


CONCLUSIONS
Samples collected into lithium heparin PST™ tubes show pre-analytical glucose loss at 1 h that is independent of baseline glucose and cellular count. Furthermore, immediate plasma separation using these tubes attenuates glucose loss across a wide range of glucose concentrations.
Huan
H
Chan
Helen
H
Lunt
Harmony
H
Thompson
Helen F
HF
Heenan
Christopher M A
CM
Frampton
Christopher M
CM
Florkowski
D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D001800:Blood Specimen Collection; D003920:Diabetes Mellitus / Q000097:blood*; D006801:Humans; D013997:Time Factors; D055815:Young Adult
D001786:Blood Glucose