Aug 1, 2016




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

Thrombin Time Inhibitor Screen

Thrombin Time Inhibitor Screen (HCTTIS) Coagulation Lab Test

Name: Thrombin Time Inhibitor Screen

Test Name: Thrombin Time Inhibitor Screen

Health Link Test Code: HCTTIS

LIS Test Code: TTIS

CPT Code(s): 85670x2

Methodology: Photo-Optical Clot Detection

Clinical Information:

Also known as a "mixing study". An inhibitor screen is done to explain a prolonged Thrombin Time.

Days Performed: Mon-Fri, dayshift - day varies. Specimens are accepted at any time. Testing required during off hours must be approved by a Coagulation physician. Call 263-5005 before collection.

In-Lab Turnaround Time: 4 - 10 days.

Stat In-Lab Turnaround Time: 1 day.

Patient Preparation:

Patient MUST be off heparin for at least 72 hours and off direct thrombin inhibitor for 24 hours prior to specimen collection.

Specimen: Blood

Collection Container: Light blue top (3.2% NaCitrate)

Collection Instructions:

Do NOT draw through a line containing heparin. The venipuncture MUST be atraumatic to avoid hemolysis and contamination with tissue factors and platelets. Tube must be allowed to fill completely.


Please indicate patient history and if patient is receiving anticoagulant (Coumadin/Heparin/Vitamin K antagonist), direct thrombin inhibitor or fibrinolytic agent therapy and duration.

Collection Volume: Four full 3.5 mL tubes

Pediatric Collection Volume: 2 full pediatric tubes filled to mark

Stability Ambient:

4 hours on a spun tube

Stability Refridgerated:

Not acceptable

Stability Frozen:

2 weeks at -20°C; 6 months at -70°C

Sample Analyzed: Plasma

Testing Volume: 5 mL

Pediatric Testing Volume: 1.5 mL

Specimen Processing:

Ultracentrifuge sample and label "ULT". If an ultracentrifuge is not available, centrifuge tube to obtain platelet poor plasma (platelet count should be 10 K/uL or less). Separate plasma from cells and transfer to plastic tube and spin again. Transfer plasma from second spin to clean plastic tube or vial. Indicate on tube "spun twice". Freeze plasma within 4 hours of collection at -20°C or below.

Specimen Transport:

Transport whole blood specimen at room temperature to UWHC Laboratory within 4 hours of collection. See Specimen Processing for instructions if transport criteria are not met. Transport frozen plasma aliquot on dry ice to UWHC Hospital Laboratory.

Unacceptable Criteria:

Hemolyzed specimens, clotted specimens, partially filled tubes and whole blood specimens greater than 4 hours old when received by the laboratory are not acceptable.


18 years and up: Negative for an inhibitor

Interpretation Type: Reference Interval

Additional Information:

The presence of an inhibitor can be ascertained by performing a Thrombin Time before and after the incubation of a 1:1 mixture of patient plasma and normal plasma.