The role of ethylenediamine tetraacetic acid (EDTA) as in vitro anticoagulant for diagnostic purposes Original paper

What was reviewed?

This narrative review evaluated EDTA anticoagulant diagnostic sample stability across routine and emerging laboratory applications, focusing on how EDTA’s calcium-chelation and broader metal-ion complexation influence specimen integrity, analyte stability, and analytical bias. The authors summarized evidence for EDTA (including K2EDTA and K3EDTA) as an in vitro anticoagulant for hematology and extended uses in cytokine testing, peptide/protein stabilization, cardiac biomarkers, proteomics, drug monitoring, molecular biology/virology, and selected clinical chemistry assays, while emphasizing preanalytical pitfalls (tube filling, storage time/temperature, and cross-contamination) and the ongoing search for “universal” anticoagulants.

Who was reviewed?

Rather than evaluating a single patient cohort, the review synthesized findings from methodological, analytical, and clinical laboratory studies involving human blood specimens processed under varied anticoagulant conditions. The scope spans routine clinical populations (including thrombocytopenic patients where EDTA-dependent artifacts are more frequent), biobanked samples (long-term storage), and research settings (cytokine induction experiments and proteomics workflows). The review also incorporated evidence relevant to special contexts such as athletes (sample stability for hematology indices) and infectious disease diagnostics (PCR-based viral load and nucleic acid stability), meaning the “who” is effectively the broad clinical laboratory population whose results depend on correct tube selection and handling.

Most important findings

EDTA remains the anticoagulant of choice for hematology because it best preserves cellular morphology and supports reliable CBC parameters, with generally excellent short-term stability for many indices when samples are refrigerated (commonly acceptable up to 24 hours for most CBC parameters, with more time-sensitive behavior for platelet volume and reticulocyte-related indices). However, EDTA does not fully stabilize platelets: mean platelet volume can drift with time-from-draw, and EDTA can trigger EDTA-dependent pseudothrombocytopenia via in vitro platelet clumping (prevalence ~0.1% overall, higher in thrombocytopenic patients), risking misdiagnosis and unnecessary interventions. EDTA is also strongly recommended for cytokine handling because it stabilizes blood pre-centrifugation, yet it can bias specific cytokines (notably TNF-α in some contexts) and is not recommended for certain soluble receptors due to spurious results. For labile peptides/proteins (e.g., PTH, ACTH, glucagon), EDTA improves stability—often enhanced by protease inhibitors—making it highly valuable for endocrine and proteomic workflows, where preanalytical timing can dominate signal patterns. Conversely, EDTA’s metal chelation limits routine chemistry (it invalidates calcium/iron/magnesium measurement and complicates sodium/potassium interpretation), and it can interfere with some cardiac troponin immunoassays, so serum or alternative anticoagulants are preferred there. Overall, EDTA’s “stabilizer” identity is strongest for cells, nucleic acids (PCR compatibility vs heparin inhibition), and protease-sensitive analytes, while its biggest risks are platelet-related artifacts, electrolyte/metal distortion, and cross-contamination causing spurious hyperkalemia.

Key implications

For clinicians interpreting lab results, the message is delightfully unromantic: the tube matters as much as the test. EDTA is excellent when you need intact cells, stable nucleic acids, or protection of protease-labile peptides—but it can manufacture disease-looking artifacts (notably false thrombocytopenia and misleading potassium/calcium patterns via contamination). Practically, unexpected thrombocytopenia should prompt smear review and/or repeat testing in citrate or another suitable anticoagulant, and cardiac troponins should generally avoid EDTA unless assay-validated. For translational microbiome work, this paper provides a crucial preanalytical warning: EDTA may be ideal for host biomarker preservation, but it does not supply organism-level microbiome associations; any microbiome signatures database would use it only to annotate specimen processing conditions that can bias immune and metabolite readouts rather than microbial taxa per se.

Citation

Banfi G, Salvagno GL, Lippi G. The role of ethylenediamine tetraacetic acid (EDTA) as in vitro anticoagulant for diagnostic purposes.Clin Chem Lab Med. 2007;45(5):565-576. doi:10.1515/CCLM.2007.110