LQPB2603 - CMLE - Collection of Coagulation Specimens-Collection of Coagulation Specimens

Collection of Coagulation Specimens

Pdf Summary

This phlebotomy module focuses on best practices for collecting and handling coagulation specimens to prevent pre-analytical errors that can cause clinically dangerous, misleading results. It opens with a case of a 72-year-old man on warfarin whose initial INR was critically high (10.3) despite no bleeding symptoms. Investigation revealed a difficult draw using a small needle and syringe with strong suction, producing a hematoma and, importantly, an underfilled citrate tube. Because underfilling disrupts the required 9:1 blood-to-anticoagulant ratio, clotting times can be falsely prolonged. A properly recollected specimen (minimal tourniquet time, appropriate collection set, discard tube) yielded a therapeutic INR of 2.4, avoiding unnecessary reversal therapy and hospitalization.<br /><br />The document reviews anticoagulants and tube selection: sodium citrate (light blue top, 3.2% preferred) is the standard for PT/INR and aPTT because it reversibly binds calcium and preserves coagulation factor activity; EDTA (lavender top) strongly chelates calcium and is used for CBCs while preserving cell morphology; heparin works by activating antithrombin III. Correct order of draw and appropriate devices are emphasized; butterfly draws require a discard tube to fill tubing. Fingerstick/heelstick samples are inappropriate for coagulation testing.<br /><br />Handling requirements include filling tubes to the line, gentle inversion (about 6 times), inspecting for clots, and prompt processing (separate plasma within 30–60 minutes; many labs set a 3–4 hour acceptability limit). Platelet-poor plasma should be prepared, aliquoted into labeled plastic tubes, and frozen within 4 hours, avoiding repeat freeze–thaw cycles. Special adjustments are needed when hematocrit exceeds 55% (citrate volume must be reduced). Common error sources include hemolysis, mislabeling, transport delays, lipemia/icterus interference on some platforms, and heparin contamination (especially from vascular access devices). Overall, accurate phlebotomy is framed as essential to patient safety and correct anticoagulation management.

Keywords

coagulation specimen collection

pre-analytical errors

PT/INR testing

aPTT testing

sodium citrate light blue top tube

9:1 blood-to-anticoagulant ratio

citrate tube underfilling

warfarin INR case study

discard tube for butterfly draw

platelet-poor plasma processing and freezing