Return to Test Directory
Inhibitor Screen (8000100309)
Test Mnemonic:

Inhibitor Screen

Specimen Requirements:

Fill within ±10% from stated capacity. Immediately after draw, gently invert 3-4 times.

Test Included:

PT inhibitor screen

aPTT inhibitor screen



Routine venipuncture; discard 1st mL of blood by collecting a discard tube prior to collecting the blue-topped (3.2% sodium-citrate) tube.  For collections with butterfly blood collection sets, a discard tube should also be collected prior to collection of the blue top to ensure sufficient sample volume. Drawing a discard tube will displace the air from the blood collection set tubing to ensure proper blood draw volume. 


 Blue-topped (3.2% sodium-citrate) tube

Minimum Volume:

2 mL of plasma 


If delivery time is to be greater than 4 hours from time of draw, centrifuge the specimen for 15 minutes at 2000-2500g

  • Transfer plasma to 12x75 plastic tube
  • Cap tube and re-spin  for 15 minutes at 2000-2500g
  • CAREFULLY remove from centrifuge without disturbing any platelets and/or cell pellets that might be on the bottom or sides of the tube.
  • Carefully transfer plasma into freezer tubes (plastic screw-top cryo-tubes) for testing or freezing.
Specimen Preparation:

Samples should be received in laboratory within ½ hour of draw for best results.


Whole blood 4 hours at room temperature. Plasma 8 hours at 20+/- 5°C.  Frozen at -20 °C 2 weeks.  

Causes for Rejection:

QNS, clotted, severely hemolyzed specimen, wrong tube, high hematocrit (> 55%), sample identification error, sample processed/transported, and/or stored improperly.

Reference Range:


Turnaround Time:

The hours of operation are Monday – Friday from 8:00 am to 4:00 pm with an expected TAT of 4 hours. STAT requests after business hours will be evaluated and handled by the on-call staff member.



Optical Density


Samples are accepted 24 hours per day at Sample Management, 7.412 CSW Bldg.



CLS Specialty Lab

Click to view CLS Specialty Lab website 



Mixing Study, PT 1:1 Mix, APTT 1:1 MIX

Clinical Indication:

This test is used for the evaluation of the presence of an inhibitor to a clotting factor.

Patient Preparation :

Samples should be received in laboratory within ½ hour of draw for best results.  

CPT 4 Code:


When ordering tests for which Medicare or Medicaid reimbursement will be sought, physicians should only order tests that are medically necessary for the diagnosis or treatment of the patient. Components of the organ or disease panels may be ordered individually. The diagnostic information must substantiate all tests ordered and must be in the form of an ICD-10 code or its verbal equivalent.
Return to Test Directory