Thrombin time
(TT)

Sample type:

Citrated Plasma (& Brown clotted serum, gel barrier if part of a thrombophilia screen)

Uses:

TT measures the time of conversion of fibrinogen into fibrin once thrombin (used as a reagent) is added

Precautions: no specific precautions needed

Interfering factor:

• The assay is sensitive to low concentrations of heparin provided the tested plasma is collected without activation and release of platelet alpha granules, which contain PF4, a heparin inhibitor.

• Various drugs or treatments can affect TT results. An additional investigation should be realized to determine the origin of each unexpected abnormal result.

Pre-analytical errors:

• collection of blood specimens

• prolonged tourniquet placing

• inappropriate mixing of a sample

Corrective action

• good mixing for the sample

• proper collection of the sample

Post analytical errors:

• Check instrument settings

Reference range:

14-21 second