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Test Code LAB325 PTT

Clinical Information

Evaluation of intrinsic coagulation system, aid in screening for presence of classical hemophilia A and B, Christmas disease, congenital deficiencies of factors II, V, VIII, IX, X, XI and XII, dysfibrinogenemia, disseminated intravascular coagulation, liver failure, congenital hypofibrinogenemia, vitamin K deficiency, congenital deficiency of Fitzgerald factor and prekallikrein.

Synonym

  • PTT
  • Partial Thromboplastin Time
  • aPTT
  • Activated Partial Thromboplastin Time

Specimen Required

Preferred Container/Tube: 3.2% Citrate Blue Top - 2.7 mL
Specimen Volume: 2.7 mL
Acceptable Container/Tube: 3.2% Citrate Blue Top - 1.8 mL
Specimen Volume: 1.8 mL
Platelet poor plasma (PPP):
Specimen Volume: 2 - 1 mL aliquots platelet poor plasma (PPP)
Specimen Minimum Volume: 1 - 1 mL aliquot platelet poor plasma (PPP)

Specimen Collection Information

For Outreach, other than OSU Patient Service Centers: Samples must be processed and received frozen/must remain frozen in transit. 

For sending frozen plasma specimens, process immediately upon receipt. Centrifuge capped specimen tube in accordance with CLSI H21, at a speed and time required to consistently produce platelet-poor plasma (PPP = platelet count <10 K/uL). Transfer PPP into plastic aliquot tubes, cap and freeze. DO NOT transport until specimens are completely frozen.

Specimen Stability Information

Ambient: 
     Whole blood: 4 hours
     Capped and centrifuged: 4 hours
     Centrifuged and plasma separated from cells: 4 hours
     Platelet poor plasma: 4 hours
Frozen: 
      Platelet poor plasma: PPP removed from the cells and frozen at -20°C or ideally -70°C.

Rejection Due To

  • Ambient WB specimens >4 hours
  • Ambient PPP specimens >4 hours old
  • Clotted specimens
  • Underfilled or overfilled tube
  • Hemolysis

Reference Values

24.0-34.3 sec

Cautions

Blood specimens from patients treated with lytic agents usually contain heparin that adds to the prolongation of the PTT. Patients with abnormally elevated hematocrits may show falsely prolonged PTT.

Method Description

Mechanical clot detection initiated by Calcium in the presence of cephalin (platelet substitute) and a particulate activator (silica).

Performing Lab

Clinical Lab UH
Clinical Lab University East
Clinical Lab James
Clinical Lab Martha Morehouse
Clinical Lab Spielman
Clinical Lab West Campus

Day(s) Performed

Monday through Sunday

Report Available

Same day/1 day

Reporting Name

PTT

CPT Code Information

85730

LOINC Code Information

14979-9