Blood glucose determination: plasma or serum?

BACKGROUND: Blood glucose determination is one of the most common clinical diagnostic tests. Often, blood is collected in a field station and analysis is carried out in a remote laboratory. Because blood cells can continue to metabolize glucose, the time of determination of blood glucose after drawing the blood is important.

METHOD: In order to test the relative suitability of plasma and serum for blood glucose determination, fluoride plasma and Ethylene Diamine Tetra Acetic acid (EDTA) plasma were compared with the serum of the same patient. The analyses were carried out within 10 min of drawing the blood and, thereafter, with a gap of 4 hr and 8 hr.

RESULTS: Serum gave values lower than fluoride plasma by 1.15%. Although this difference was statistically significant, it may not be physiologically relevant. Hence, serum may be used for blood glucose determination with an error of 1.15%. On storing the sample at room temperature for 8 hr, the serum glucose value decreased by 8%. Even fluoride plasma had 4.3% lower glucose.

CONCLUSION: Hence, blood glucose should be determined within as short a time as possible after drawing the blood.