Effect of Pneumatic Tube System Transport on Serum and Plasma Enzyme Levels

Pneumatic tube systems of various lengths are routinely used in many hospitals to transport blood collection tubes (serum, plasma, whole blood) to the testing laboratory. The present study evaluated the changes in the levels of enzymes in two different tube system transports within the hospital system. Two tubes of blood, one SST (Serum) tube and one Lithium Heparin (Plasma) tube, were collected simultaneously from 31 (Site 1) and 22 (Site 2) volunteers. Both tubes were hand carried to the lab and levels of LDH, AST, ALT, ALK PHOS, GGT and K were measured. These tubes were then hand-carried back to the site of collection and transported to the testing lab respective site pneumatic tube systems. The average carrier travel distance for Site 1 is 2911 feet and Site 2 is 1200 feet. Average travel sped of carriers at both locations is 28 feet per second. Both serum and plasma enzyme levels were measured using AU 680 and analyzer (Beckman Coulter Inc, Brea CA). Significant differences between plasma levels of LDH are observed when comparing the results of untubed blood vs. blood transported through pneumatic tube system. The length of travel of the tube has significant influence on various analytes and percent bias is high for ALT and AST at Site 1, but these differences are not statistically significant. On the other hand no significant differences are observed in serum levels of all enzymes. Hemolysis measured by Spectral index did not show any hemolysis of both serum and plasma tubes. Stability of plasma specimens are also decreased by 3 days when they are stored refrigerated. LDH levels are significantly elevated based on the length of tube travel in plasma and not in serum. Careful validation is needed when implementing plasma tubes for chemistry analytes, especially when transported through pneumatic tube systems.