Making the Diagnosis
The symptoms and signs of an acute gout attack are so obvious that a doctor can usually be quite sure of the diagnosis just from your history and physical exam. Even though gout would be the most likely diagnosis, assumptions are never completely safe, so doctors also consider other causes such as infection and other kinds of diseases when making the diagnosis.
Blood tests showing hyperuricemia can support the diagnosis, but aren't necessary for it. To confirm the diagnosis, your doctor may insert a needle into the joint and draw out some fluid to examine under a microscope. If it's gout, needle-shaped uric acid crystals inside white blood cells will show up when the fluid is viewed under polarizing light. This is a definitive diagnostic test.
It is important to measure the 24-hour urine output of uric acid in the urine (when the acute attack is over). High urine levels of uric acid would mean increased risk of kidney stones and damage, and may explain why some people's blood uric acid levels are not as high as expected.