Neuwinger et al. (2019) conducted a comprehensive analysis to determine the effect of underfilling vacuum blood collection tubes on lactate dehydrogenase (LD) activity. Underfilling tubes resulted in noticeably greater LD activity, according to the study, suggesting that preanalytical circumstances may have an impact on LD measurements. I would want to investigate the specific mechanisms that cause an increase of LD activity in underfilled tubes in order to have a deeper understanding.
When blood collection tubes are underfilled, the elevation of lactate dehydrogenase (LD) activity is mainly caused by the increased shear stress on blood cells and processes that result in cell breakdown. Inadequate filling of tubes can cause added stress on blood cells during processing, leading to the release of LD and other cell components, which in turn increases LD activity. Differences in the additives' concentration in underfilled tubes compared to properly filled tubes can also play a role in this elevation. These particular mechanisms, such as shear stress, cell breakdown processes, and additive concentration, can cause falsely elevated LD activities in underfilled tubes.
References: Neuwinger, N., Meyer zum Büschenfelde, D., Tauber, R. (2019). Underfilling of vacuum blood collection tubes leads to increased lactate dehydrogenase activity in serum and heparin plasma samples. Clin Chem Lab Med, 58(2), 213-221.
Several distinct mechanisms may be responsible for the increase in lactate dehydrogenase (LD) activity seen in vacuum blood collecting tubes that are not fully filled. Insufficiently filling blood tubes leads to a higher likelihood of blood being drawn in too quickly, which might put more strain on blood cells during collection. The application of shear stress may result in mechanical damage to the cells, leading to the liberation of intracellular constituents, such as LD, into the serum or plasma specimen. Furthermore, tubes that are not filled to their maximum capacity may fail to maintain the optimal blood to anticoagulant ratio, thereby affecting the stability of the sample and leading to hemolysis. Hemolysis may result in an elevation in LD levels due to the liberation of LD from compromised red blood cells. The convergence of these processes, which include cell damage due to shear stress and hemolysis, results in the observed elevation in LD activity in tubes that are not completely filled. Therefore, it is crucial to guarantee precise tube filling, reduce shear stress during blood collection, and maintain the appropriate blood to anticoagulant ratio to prevent misleading elevations in LD activity in serum and plasma samples obtained from vacuum blood tubes.
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