History of exam. Most cases of classic acute sinusitis can be diagnosed by a good history: 1) nasal congestion 2) sinus pressure 3) sinus pain 4) tooth pain 5) ear pain 6) purulent drainage 7) fatigue and malaise. Not all have to be present for you to have a sinus infection. A good rule of thumb "if you have a cold more than 7 days. It is likely a sinus infection." chronic sinusitis has to be diagnosed with a ct.
Many. A history and physical examination are usually all that is necessary. A ct scan of the sinus may needed. Scoping the sinuses (nasopharyngoscopy) is also very helpful in difficult situations.