EDTA tubes contain an anticoagulant that binds calcium, preventing blood from clotting for various laboratory tests. Their primary uses include hematology tests like complete blood counts (CBCs), identifying parasites and bacteria, molecular diagnostics for genetic material, and measuring certain proteins and peptides. The tubes typically have lavender or purple tops and must be inverted 5-8 times after blood collection to mix the anticoagulant with the blood.