On examination, if three of the cardinal symptoms are present a provisional diagnosis of PD may be made. A positive response to levodopa is often a further indicator of correct diagnosis.
Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) are often carried out to rule out other diagnosis. The neurological changes within the basal ganglia are not routinely visible on these investigations.
In its classical presentation PD may be easily diagnosed due to the typical posture, gait and facial changes however diagnosis of early disease is challenging because in excess of 70% of substantia nigra pars compacta cells may be lost before any clinical signs are apparent.
Autopsy based studies have shown that diagnostic accuracy is imperfect with up to 25% of cases indicating an erroneous diagnosis of Pd at the time of death.
There are currently no biological markers available that will lead to a definite diagnosis of PD during life there have been some recent Australian advances. These are the initial development of a blood screening process to identify the genes implicated in Pd and another laboratory test to measure the levels of the protein alpha-synuclein in the blood. This protein is implicated in PD as PwP have low levels while people without PD have high levels. These laboratory tests are undergoing further development and trial.
In addition to Idiopathic PD there are some conditions, known as Parkinson’s Plus, which may initially mimic PD. It is often with the progression of time and presentation of additional symptoms that these conditions may be diagnosed.
