Which positive test is used to identify deep vein thrombosis?

Homan's sign is specifically designed to help identify deep vein thrombosis (DVT), making it the correct choice. This clinical test involves dorsiflexion of the foot while the knee is extended, which can provoke pain in the calf if a DVT is present. The rationale behind this is that the tension created in the calf muscles may compress a clot in the deep veins, leading to discomfort.

In contrast, McMurray's test is primarily used to assess meniscus injuries in the knee, Lachman's test evaluates the integrity of the anterior cruciate ligament, and Ober's test is designed to assess tightness in the iliotibial band. Each of these tests serves a different purpose related to other injuries or conditions and is not applicable to the identification of deep vein thrombosis. Thus, Homan's sign stands out as the relevant test in this context.