Parkinson's disease: a scoping review of the quantitative and qualitative evidence of its diagnostic accuracy in primary care.

Background: Parkinson's disease is a multisystem condition that usually presents as a movement disorder in clinical practice. There is no objective method for its diagnosis and therefore the current diagnostic process is based on characteristic clinical signs and symptoms. As the presenting symptoms can be vague and non-specific, there is often a delay in diagnosis leading to mismanagement and delayed treatment initiation. In the UK, GPs identify and initially assess individuals with Parkinson's disease and refer them to specialists for formal diagnosis and treatment initiation.

Aim: To use a scoping review to examine the available evidence on the accuracy of Parkinson's disease diagnosis in primary care and to assess the potential for GPs to make a diagnosis and initiate treatment, and hence avoid harmful delays.

Design And Setting: The scoping methodology as proposed by Westphaln and colleagues that is a modified version of Arksey and O'Malley's original framework was followed. All findings were reported according to PRISMA guidelines for scoping reviews.

Method: Four databases (EMBASE, PubMed Central, Cochrane, and CINAHL) and references lists of relevant published literature were systematically searched for all types of literature available in English on the accuracy of Parkinsonism or Parkinson's disease diagnosis in primary care. There were no search restrictions placed on countries, type of studies, or age. Two reviewers independently screened titles and abstracts followed by full-text screening.

Results: Out of 1844 studies identified, only six studies met the inclusion criteria. Five were from high-income and one from a middle-income nation. Of these, three studies identified significant knowledge gaps of GPs in diagnosing Parkinson's disease using a questionnaire-based assessment. Delay in appropriate referral because of delayed symptom identification was reported in one study. Only one study compared the accuracy of primary care Parkinson's disease diagnosis with that of specialists, and reported that, although specialists' diagnosis showed more sensitivity, GPs had higher specificity in diagnosing Parkinson's disease. However, this study was found to have methodological issues leading to bias in the findings.

Conclusion: This scoping review shows that there are no well-conducted studies assessing the accuracy of Parkinson's disease diagnoses when made by GPs. This calls for more focused research in this area as diagnostic delays and errors may lead to potentially harmful but preventable delays in treatment initiation resulting in decreased quality of life for individuals with Parkinson's disease.