Autor:innen:
Dr. med. Nick Neuwinger | Charité-Universitätsmedizin Berlin | Germany
Dr. Dirk Meyer zum Büschenfelde | Charité-Universitätsmedizin Berlin | Germany
Prof. Dr. med. Rudolf Tauber | Charité-Universitätsmedizin Berlin | Germany
Prof. Dr. med. Kai Kappert | Labor Berlin - Charité Vivantes GmbH | Germany
BACKGROUND: The activity of lactate dehydrogenase (LDH) is routinely monitored, e.g. for stratification of malignant diseases, but is susceptible to preanalytical influences.
METHODS: Blood was withdrawn by antecubital venipuncture from healthy volunteers and collected in vacuum blood collection tubes (serum, SE; heparin plasma, HP). The tubes were either filled completely (≥90% of volume), or were underfilled to approximately 50%. Thereafter, tubes were centrifuged directly or stored at room temperature for 4 h prior to centrifugation. We systematically analyzed potassium, sodium, chloride, LDH, creatine kinase, total cholesterol, and indices for hemolysis, icterus, and lipemia. In a subset of tubes we also measured blood filling velocity. Finally, in an in-patient cohort of more than 74,000 patients, we analyzed plasma yield and data distribution of LDH by means of the DGKL Reference Limit Estimator (RLE) to reconfirm our findings in healthy volunteers.
RESULTS: The activity of LDH was higher in HP tubes compared to SE. The reduction of the filling volume of tubes was followed by significantly higher LDH values (SE: +21.6%; HP: +28.3%), potassium (SE: +4.2%; HP: +5.3%), and hemolysis index (SE: +260.8%; HP: +210.0%). In contrast, levels of other analytes remained generally stable. The filling velocity of blood in the collection tubes was approx. 3-fold higher in the first compared to the second half with no differences between HP and SE. Notably, the plasma yield in the routine patients cohort also inversely correlated with the activity of LDH. Estimation of reference limits for LDH revealed established intervals only in patients’ tubes that were adequately filled.
CONCLUSIONS: The reduction of filling volume in both SE and HP collection tubes leads to significant increases in LDH activity, both in healthy volunteers and in inpatients. This may be considered in cases of clinically implausible enhanced levels of LDH.