Practice Guidelines for Parkinson's disease.

'Practice Guidelines (PG) or treatment guidelines' are not infallible guidelines but tools with which to support a clinical decision, i.e. one factor when making a clinical decision. When making a clinical decision, medical practice is determined by taking into consideration PG, a patient's preferences, and a country's social and healthcare systems. Even if a PG provides a treatment method based on a high-level of evidence, the method simply represents a mean result obtained from past clinical studies, which are not always uniformly applicable to all patients. When consulting a PG, it is advisable to know in advance what group/society/organization prepared it, the purpose of its preparation, and the developmental method, including social equity, whether healthcare costs are assumed in the PG or whether the pharmaceutical industry had substantial involvement in its development. Thus, PGs need to be developed according to the actual conditions in a country or institution. As to the questions whose answers are not provided in a PG, these issues have to be defined and assessed through a literature search. This is the so-called implementation of Evidence-Based Medicine (EBM). The concepts of EBM further require the provision of better evidence. A PG is always fated to be out of date by the time it is published because new evidence is continually being published. It is therefore, always necessary to search for the most up to date evidence available.