Relationship between sampling volume of primary serum tubes and spurious hemolysis.

Background: We planned a study to establish whether spurious hemolysis may be present in low volume tubes or partially filled tubes.

Methods: Four serum tubes were collected in sequence from 20 healthy volunteers, i.e., 4.0 mL, 13 x 75 mm (discard tube), 6.0 mL, 13 x 100 mm half-filled, 4.0 mL, 13 x 75 mm full-draw and 6.0 mL, 13 x 100 mm full-draw. Serum was separated and immediately tested for hemolysis index (HI), potassium, aspartate aminotransferase (AST), and lactate dehydrogenase (LDH).

Results: The HI always remained below the limit of detection of the method (< 0.5 g/L) in all tubes. No statistically significant differences were recorded in any parameter except potassium, which increased by 0.10 mmol/L in 4 mL full-draw tubes. No clinically significant variation was however recorded in any tube.

Conclusions: The results suggest that all types of tubes tested might be used interchangeably in term of risk of spurious hemolysis.