Final answer:
A positive test for De Quervain's Tenosynovitis is the Finkelstein test.
Step-by-step explanation:
A positive test for De Quervain's Tenosynovitis is the Finkelstein test.
During the Finkelstein test, the patient makes a fist with their fingers closed over their thumb, and then bends their wrist towards the side of the little finger. If this maneuver reproduces pain on the side of the wrist, it is considered a positive test.
The other options mentioned, Phalen's test, Tinel's sign, and Valgus stress test, are not specifically used in the diagnosis of De Quervain's Tenosynovitis.