Apathy and depression scales in Parkinson's disease: are they good enough?

The choice of a scale has important implications for the results of clinical research, including epidemiological and treatment studies. In addition to the requirements for any clinical scale, evaluation of rating scales for depression and apathy in Parkinson's disease (PD) faces additional challenges, reflecting the overlap of syndromes, controversies on the concept particularly of apathy, fluctuations related to medication, and difficulties in assessment. However, a number of rating scales are available which have been assessed for use in patients with PD, and the evidence for the use of these scales is discussed. A number of scales fulfil the basic requirements but further studies on their properties are required. Scales for screening need to have different properties than scales for rating severity. Overall, there is no perfect scale, but the choice of scale needs to take into account clinimetric properties, validity in the sample examined, content and purpose.