The EDTA K2 blood collection tube, containing dipotassium ethylenediaminetetraacetic acid (EDTA-K₂) as an anticoagulant, functions by chelating calcium ions in blood to inhibit the coagulation cascade, thereby preserving the original morphology of blood cells ex vivo. Its clinical roles and significance include:

1. Gold Standard for Hematology Testing: As the preferred anticoagulant for complete blood count (CBC) and blood smear examinations, it ensures accuracy in white blood cell differentials, red cell morphology, and platelet counts;

2. Cellular Stability Maintenance: EDTA-K₂ prevents platelet aggregation and minimizes cell lysis, making it critical for assays requiring intact cells (e.g., flow cytometry for CD4/CD8 counts);

3. Standardized Laboratory Practice: Recommended by the International Council for Standardization in Haematology (ICSH) for routine hematology testing, ensuring result comparability and reliability;

4. Diagnostic Value: Provides essential data for screening, diagnosing, and monitoring conditions such as anemia, infections, hematologic malignancies (e.g., leukemia), and thrombotic disorders.

Note: Gently invert the tube 8-10 times post-collection; samples should be analyzed within 4 hours to prevent cellular degradation affecting results.