Partial Thromboplastin Time
General Information
Lab Name
Partial Thromboplastin Time
Lab Code
PTT
Epic Name
Partial Thromboplastin Time
Description
Partial Thromboplastin Time (PTT) is a screening test for the assessment of congenital and acquired deficiencies of the intrinsic (factors VIII, IX, XI and XII) and common (factors II, V, X and fibrinogen) pathway coagulation factors. It is also used to detect the presence of coagulation inhibitors such as lupus anticoagulant and specific factor inhibitors. PTT can be used to monitor unfractionated heparin therapy although Anti-Xa for Heparin Infusion (HIXA) is the preferred test for heparin monitoring.
Synonyms
aPTT
Components
| Code | Name |
|---|---|
| PTTPAT | PTT Patient |
| PTTXM | PTT X_Mean |
Interpretation
Method
Clot based
Reference Range
See individual components
Ref. Range Notes
For information regarding the use of this test for anticoagulant monitoring, visit UW Medicine Anticoagulation Services
Ordering & Collection
Specimen Type
Collection
2, 3 or 5 mL BLUE TOP (CITRATE) tube
Pediatric draws: (At UW-MT ONLY) Contact the lab at 598-6242 and ask for a baby draw tube for coagulation testing.
Note: Blood dilution and contamination with heparin are risks if specimen is collected from an arm with indwelling catheter. If arm must be used, turn off the IV for NO LESS THAN 5 MINUTES before performing a peripheral draw.
If sample is collected through the catheter, turn off the IV, flush the catheter with saline and discard a waste sample before drawing the sample for the PTT. (See Nursing Policies and Procedures for details.)
Handling Instructions
UW-MT/HMC: For Heparin monitoring on inpatients, specimen MUST be processed within 1 hour.
All other PTT requests, process within 6 hours of blood collection.
UW-NW only: specimens MUST be processed within 4 hours of blood collection.
FHCC: Specimens must be processed within 4 hours of collection.
Quantity
requested: entire specimen
minimum: 1.0 mL Citrated plasma
Processing
Take specimen to Coag
Outside Laboratory: Centrifuge for 10 minutes, remove plasma & re-spin plasma for another 10 minutes. Decant & Freeze plasma (minimum 1.0 mL) @ -20°C to -80°C. Send Frozen on dry ice.
Stability: plasma samples frozen at -70°C or below are good for 1 year
Performance
LIS Dept Code
Coagulation (COAG)
Performing Location(s)
| HMC |
Coagulation
206-520-4600 325 9th Ave, Rm # GWH-47, Seattle, WA 98104-2420 |
|
|---|---|---|
| UW-NW |
Main Lab
206-668-1344 UW Medical Center – Northwest |
|
| FHCC |
Fred Hutch Alliance Lab
206-606-1088 825 Eastlake Ave, Seattle, WA 98109 |
|
| UW-MT |
Coagulation
206-520-4600 Clinical Lab, Room NW220, |
Frequency
Daily
Available STAT?
Yes