Uncovering Hidden Traces of K2EDTA Contamination in Citrated Blood Samples: A Novel Approach Using Fibrinogen Clot Waveform Graphs.

Background: Preanalytical mistakes in coagulation assays to a great extent affect diagnostic results. K₂EDTA contamination is one of the preanalytical mistakes that significantly interferes with assays of prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, and thrombin time (TT).

Objective: To assess how different levels of K₂EDTA contamination influence coagulation test results and to evaluate the effectiveness of clot waveform analysis in identifying such contamination in citrated blood samples.

Methods: Contamination was introduced at varying concentrations (5%, 13%, 17%, 29%, 33%, 43%, and 100%) in citrated whole blood samples from 36 healthy volunteers. Coagulation assays for aPTT, PT, fibrinogen, and TT were performed using the Sysmex CN 6000 analyzer. Clot waveform analysis was used to detect contamination.

Results: The results revealed significant differences from the reference ranges for aPTT at contamination above 17% K₂EDTA and at 29% in PT and fibrinogen. As far as TT is concerned, significant changes were found from a contamination of 33%. Notably, fibrinogen second-derivative graphs showed min2 values above 0.31, with a sensitivity of 80.3%, specificity of 99.3%, and an area under the curve (AUC) of 0.94. These changes indicated a high likelihood of K₂EDTA contamination.

Conclusions: K₂EDTA contamination above 17% can significantly alter coagulation test results, potentially leading to diagnostic inaccuracies. Clot waveform analysis, particularly fibrinogen second-derivative graphs, can detect contamination, and proper sample collection guidelines are crucial for accuracy.