Partial Thromboplastin Time (PTT)
Department: Coagulation
Test Synonym(s): LAB325, aPTT, Activated Partial Thromboplastin Time, PTT
CPT Codes: 85730
Methodology: Clotting
Reference Range: 23.5-33.5 seconds
Tube Type: Light blue top (Sodium Citrate)
Specimen: Citrated platelet poor plasma - Requires double centrifugation if sending a plasma aliquot. Aliquot(s) must be frozen if not received by lab within 4 hours of collection.
Alternate Specimen: None
Pediatric Requirements: Pediatric: One 2.7mL Light blue top - 3.2% Sodium Citrate. Neonatal: One 1.8mL Light blue top - 3.2% Sodium Citrate.
Volume: 1.0 mL plasma
Minimum Volume: 1.0 mL plasma
Temperature: Room Temperature for Light blue top tube, must be received within 4 hours of draw. Plasma aliquot(s) must be frozen if not received by lab within 4 hours of collection.
Stability: Room temperature: 4 hours, if patient is on Heparin: 2 hours
Reasons for Rejection: Clotted sample, incorrectly filled tubes, incorrect tube type, grossly hemolyzed sample, grossly lipemic sample, grossly icteric sample, whole blood >4.0 hours old
Days Performed: Daily
Times Performed: Continuous
TAT: 2 hours, once received into the lab
Significance: Direct Thrombin and both Direct and Indirect Xa inhibitors may interfere with these assays. Therapeutic levels of coumadin may cause a prolongation of the PTT. PTT is not appropriate for monitoring LMWH or direct Xa Inhibitors
Special Instructions: Indwelling line should be flushed with saline and 5.0 mL of blood discarded before collecting samples for coagulation assays. Tube must be full and not clotted. Deliver to lab immediately. Samples received from an outside lab must be aliquoted and frozen. Samples aliquoted for shipping must be double centrifuged prior to freezing. Grossly hemolyzed, icteric or lipemic samples may be rejected.
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