There are currently no blood or laboratory tests that diagnose sporadic PD. Therefore the diagnosis is based on medical history and a neurological examination. In some cases PD can be difficult to diagnose accurately early on in the course of the disease. Early signs and symptoms of PD may sometimes be dismissed as the effects of normal aging. Doctors may sometimes request brain scans or laboratory tests in order to rule out other disorders. However, computed tomography (CT) and magnetic resonance imaging (MRI) brain scans of people with PD usually appear normal. Since many other diseases have similar features but require different treatments, making a precise diagnosis is important so that people can receive the proper treatment.