Which of the following is NOT used by a general practitioner to diagnose DVT?

A general practitioner typically relies on various clinical signs and tests to diagnose deep vein thrombosis (DVT), including Homan's sign, Bancroft's sign, and Lowenberg's sign. However, the tourniquet test is not a standard assessment used for diagnosing DVT in routine clinical practice.

Homan's sign involves assessing for calf pain upon dorsiflexion of the foot, which may suggest DVT, although it is not definitive. Bancroft's sign is associated with swelling and pain that can help in identifying venous thrombosis. Lowenberg's sign involves measuring the pressure at which pain is elicited in the calf when using a sphygmomanometer, further indicating potential DVT by evaluating the response under increased pressure.

The tourniquet test, though it may have applications in other contexts, does not specifically diagnose DVT and is not commonly used by general practitioners for this purpose. Thus, the identification of this test as not being used in DVT diagnosis is accurate, making it the correct choice in this question.