Final answer:
The most likely test result is a diagnosis of gout, which causes painful inflammation in the big toe joint. Synovial fluid analysis may be performed to confirm the diagnosis.
Step-by-step explanation:
The most likely test result for an afebrile 50-year-old male presenting with an acute onset of an exquisitely painful first MTP joint, red and swollen joint with tenderness on palpation, is a diagnosis of gout.
Gout is a form of arthritis caused by the accumulation of uric acid crystals in a joint. The crystals can cause severe inflammation and pain, especially in the big toe joint.
To confirm the diagnosis, a test called synovial fluid analysis may be performed. This involves extracting a small sample of fluid from the affected joint and examining it under a microscope to check for the presence of uric acid crystals.