The PT test monitors the adequacy of the following factor levels:
- Factor I (fibrinogen- component of common pathway)
- Factor II (prothrombin- component of common pathway)
- Factor V (component of common pathway)
- Factor VII (component of extrinsic pathway)
- Factor X (component of common pathway)
If one or more of the factors above are deficient, the PT test will be prolonged. This may indicate the need for a PT mixing study to determine the specific cause.