Light Blue Top Tube (Sodium Citrate) – (Use for Prothrombin Time or PT)


  1. To ensure result accuracy, the Light Blue Top tube requires a specific ratio of blood to anticoagulant.
    • Discard tube required for collections with a butterfly needle:
      • White Top (no additive) discard tube should be drawn prior to the Light Blue Top tube to ensure the proper blood-to-anticoagulant ratio. Drawing a discard tube displaces the air from the butterfly collection set tubing to ensure proper blood draw volume.
    • Discard tube NOT required for collections from dialysis access devices, follow your company’s policy:
      • Fistula and graft: Obtain blood specimen from the arterial needle prior to connecting the arterial blood. Do not heparinize or flush your needles until after blood is collected.
      • Catheter: Using a 10 ml syringe, withdraw any heparin and/or saline from the catheter port before collecting for laboratory testing.
      • Note: It is recommended that collection from heparinized access devices be avoided, whenever possible. If collecting via access devices where heparin and/or saline is present, consider the internal catheter volume. CLSI guidelines outline discarding a minimum of 5 mL of blood or six times the internal catheter volume for coagulation testing.
  2. Fully seat and hold the Light Blue Top tube against the back of the needle while filling. It is important not to let go of the Light Blue Top tube while it is filling, as this may stop or impede the flow of blood.
  3. Allow the tube to fill until blood flow ceases to avoid dilution errors. The tube should be filled within the nominal fill range indicated on the tube.
    • Note: Tubes not filled to the nominal fill range will be rejected as “Quantity Not Sufficient”.
  4. Immediately after drawing, gently invert the tube 4 times to activate the anticoagulant and prevent clotting.
  5. Do not centrifuge.
  6. Use the barcode label with the patient’s name and ID to identify the specimen.
  7. Hold at room temperature. Do not refrigerate.
  8. Specimens can be collected and shipped Monday through Saturday, and must be received by the laboratory within 48 hours of collection.