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Partial Thromboplastin Time (PTT)

Important Note

Alternative anticoagulants which directly inhibit thrombin (I.V.; Argatroban, Bivalirudin: Oral; dabigatran) positively interfere with APTT (e.g. direct thrombin administered concurrently with LMWH or UFH can produce a falsely elevated APTT).

Performing Lab(s)

Memorial-Belleville & Memorial-Shiloh

Methodology

STA

Specimen Requirement (s)

Specimen:  Plasma

Type: Container/Tube:  blue (sodium citrate) tube

Specimen Volume: full tube

Specimen Minimum Volume:  NA

 

Collection Instructions: NA

Lab instructions:

  • Must be performed within 2 hours of collection.

Unacceptable Conditions

  • Avoid hemolysis.
  • Short draws 
  • clotted specimens

Day(s)/Shift(s) Test Set Up and Turnaround Time

Sunday through Saturday

Hours: 24 hours

 

Turnaround Time:

STAT: 60 minutes

Routine: less than 8 hours from receipt.

Transport and Stability

Transport temperature: Ambient to lab

Reference Values

PTT

Age

Reference Values

Critical High

0 – 12 months

25 – 45 sec

≥ 180 sec

12 months – 10 years

25 – 40 sec

>10 years

22 – 37 sec

CPT/LOINC Codes

85730

Interpretive Data

 

Interpretive data

aPTT test has not been evaluated for monitoring heparin therapy. The anti-Xa is the preferred test.

Current interpretive data was last revised on 12/03/2019.