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Test Code Billings Clinic: 2003 Activated Partial Thromboplastin Time (APTT), Plasma

Performing Laboratory

Billings Clinic Laboratory: Coagulation

Useful For

  • The APTT is a useful and effective method for screening patients with a bleeding tendency, for evaluating the effect of therapy in procoagulant disorders and as the basis for several specific coagulation factor assay procedures. 
  • The presence of non-specific inhibitors, such as the lupus anticoagulant, may prolong the APTT. 
  • It can also be used to monitor unfractionated heparin therapy.

Methodology

Optical

Specimen Requirements

Specimen Collection and Handling:

  • Draw blood in a light blue-top (3.2% sodium citrate) tube(s).
  • Immediately after draw, gently invert tube(s) at least 6 times to mix well.
  • Spin down, remove plasma, spin plasma again, and place 1 mL of citrate platelet-poor plasma in plastic vial.
  • Glass vial is not acceptable.
  • Double-centrifuged specimens are critical for accurate results as platelet contamination may cause spurious results.
  • Freeze specimen immediately at -20° C.
  • Plasma containing Heparin (patients being treated with Heparin) MUST be centrifuged and plasma separated within 1 hour

 

Specimen Transport:

  • Transport specimen frozen
  • DO NOT refrigerate specimen

Storage/Stability

Specimen Type Temperature Time
Plasma (citrated) Frozen (preferred) 2 weeks
  Ambient 4 hours
  Ambient (unspun whole blood) 4 hours

 

Reject Due To

  • Clotted Specimen
  • Specimen other than Citrated Plasma
  • Visible Hemolysis
  • Incorrect fill in specimen collection tube
  • Refrigerated specimen

Reference Values

Call-back value:  ≥99.6 seconds
 

Reference values change with each new reagent lot (about once a year). Check with laboratory or refer to reference range on computer reports.

Day(s) Test Set Up

Daily

Test Classification and CPT Coding

85730 - Thromboplastin time, partial (PTT)


LCD or NCD test. ICD-10 code is required for this test. When appropriate, obtain a properly executed ABN and submit the ABN with test order(s). See “Medical Necessity and Advanced Beneficiary Notice (ABN) Policy and Form” under "Resources" for a copy of a form and additional information.

LOINC Code Information

Reporting Name LOINC Code
APTT 14979-9