In the majority of cases, sinusitis can be diagnosed based on the history of your symptoms. Sometimes a doctor may recommend  further testing, such as a scan/imaging, if symptoms are continuing for months. If you have ongoing or frequently recurring symptoms, you may also need to be referred to an Ear Nose and Throat specialist who may wish to perform a camera test (nasal endoscopy), to take a closer look at your nasal passages and sinuses. A nasal swab to test for certain infections, or tests to check for allergies may also be occasionally considered in such cases.