Dilute Prothrombin Time

Message

LabCorp

Test Code

5200

Alias/See Also

"dPT
Tissue Thromboplastin Inhibition
TTI"

Includes

"Dilute prothromboplastin time (dPT)
"

Preferred Specimen

"Plasma, frozen
"

Minimum Volume

"1 mL

"

Transport Container

"Blue-top (sodium citrate) tube

"

Transport Temperature

"Freeze
"

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

"Gross hemolysis; clotted specimen; frozen specimen thawed in transit; tubes <90% full; improper labeling; specimen collected in tube other than 3.2% citrate

"

Methodology
"Clotting time is measured using a dilute prothrombin time (dPT) reagent consisting of a unique formulation of relipidated recombinant tissue factor and calcium.8 Samples with extended dPT are tested in a confirmatory assay including excess phospholipid. The sample is considered to be positive for lupus anticoagulant when the dPT ratio (ie, dPT:confirm) is >1.15. "

Limitations

"Improper preparation of the platelet-poor plasma at collection reduces the sensitivity of this assay for LA.6,7 The screening assay can be prolonged in patients with congenital or acquired factor deficiency and will be elevated in individuals on warfarin therapy.7 The reagent contains agents that neutralize unfractionated heparin at plasma levels up to 1.0 unit/mL.7 Samples with levels higher than this can produce anomalous results.7 No single LA test can detect all LA-positive patients. The ISTH recommends that any sample suspected of having LA be tested using two or more LA screening tests.6
"

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.