A young patient is admitted from the emergency room with petechial bruising. The attending physician orders tests, including a PT and an aPTT. The laboratory performs the requested testing, and the result of the aPTT is typical, however, the PT is prolonged.
| Test | Patient Result | Reference Range |
| PT | 38 sec. | 11–13 sec. |
| aPTT | 32 sec. | 21–34 sec. |
The physician then decides to order a mixing study for further analysis since the patient is not taking any oral anticoagulants and does not meet the known patient history associated with prolonged PT results.
