Jul 25, 2016




Clinical Hub,Tools & Resources,UWHC Lab Test Directory,Coagulation


PTT (PTT) Coagulation Lab Test

Name: PTT

Test Name: PTT

Health Link Test Code: PTT

LIS Test Code: APTT

CPT Code(s): 85730

Clinical Information:


University Hospital - Optical Clot Detection

The American Center - Mechanical Clot Detection

Days Performed: Daily, 24 hours.

In-Lab Turnaround Time: 4 hours.

Stat In-Lab Turnaround Time: 1 hour.

Specimen: Blood

Collection Container: Light blue top (3.2% NaCitrate)

Collection Instructions:

The venipuncture MUST be atraumatic to avoid hemolysis and contamination with tissue factors and platelets. Tube MUST be allowed to fill up to "fill" line indicated on tube. Do not spin or open.


If unable to collect 1.8 ml tube (pediatrics only) please call UWHC Coagulation Lab at (608) 263-9617 or UWHC Special Coagulation Lab at (608)  263-5005 for alternate tube and instructions.

Collection Volume: 3.5 mL

Pediatric Collection Volume: 1.8 mL

Stability Ambient:

1 hour unspun

4 hours spun- University Hospital

2 hours spun- The American Center

Stability Refridgerated:

Not acceptable

Stability Frozen:

2 weeks at -20°C; 6 months at -70°C

Sample Analyzed: Plasma

Testing Volume: 0.5 mL

Pediatric Testing Volume: 0.5 mL

Specimen Processing:

Processing and Transport

Whole blood specimens at room temperature can be transported to University Hospital or The American Center within 1 hour of collection.


After collection centrifuge specimen to yield platelet poor plasma (platelet count should be less than 10K/uL) within one hour of collection. Separate plasma and transfer to a plastic tube or vial. For plasma at ambient temperature testing must be run within 4 hours of collection at University Hospital and within 2 hours of collection at The American Center. If greater than 4 hours (or 2 hours for TAC) freeze plasma at -20C or below. Transport frozen plasma aliquot on dry ice to the laboratory.

Unacceptable Criteria:

Hemolyzed specimens, clotted specimens, partially filled tubes and whole blood specimens greater than 1 hour old when received by the laboratory are not acceptable.



  University Hospital The American Center
 7 months and up:  28.0 - 37.0 seconds   24.0 - 35.0 seconds

The normal full-term newborn aPTT may be up to 35% longer than in adults and even longer (up to twice the adult upper limit) in healthy premature infants. 

Interpretation Type: Reference Interval

Critical Calls: yes

Additional Information:

See UWHC Pharmacy therapeutic heparin dosing guidelines.