Measurement Scales in PD
Updated: Mar 5, 2020
One of the complicating issues with Parkinson’s disease is that there are no objective markers for this disease. In other words, there is no test that we can use to determine whether someone has Parkinson’s or will develop it in the future. A significant amount of research money and effort is going towards identifying such a marker and once it is found, it will likely have significant research and clinical impact.
Until then, clinicians rely on their observational skills and the patient’s narrative to help in the diagnosis of this disease as well as ongoing evaluation as the illness progresses. There have also been a number of scales that have been developed to help clinicians assess their patients in a somewhat more defined way.
Developed initially in 1980, the United Parkinson’s Disease Rating Scale was modified by the Movement Disorder Society in 2007. The resulting MDS-sponsored revision of the UPDRS (MDS-UPDRS) consists of four parts: I: Non-motor Experiences of Daily Living; II: Motor Experiences of Daily Living; III: Motor Examination; IV: Motor Complications. Twenty questions are completed by the patient / caregiver. This scale is considered the gold standard for determining the severity and progression of Parkinson’s. But because it focuses only on nonmotor and motor aspects of the disease, it has little focus on classifying the patient’s disability due to Parkinson’s.
Another less comprehensive scale is the Hoehn and Yahr Scalewhich defines categories of motor function in Parkinson’s disease. Advantages of this scale are that is simple, easy to apply and is independent of whether the patient is receiving dopaminergic therapy. However it doesn’t cover all aspects of motor deficits and does not incorporate nonmotor aspects of Parkinson’s. Developed in 1967, it has been largely replaced by the UPDRS.
TheNonmotor Symptoms Scalewas developed with the recognition that Parkinson’s disease is not a movement disorder alone and that the nonmotor symptoms of the disease can affect quality of life and cause significant disability for patients. This scale consists of 30 items and assesses the frequency and severity of symptoms in 9 domains (cardiovascular, sleep/fatigue, mood/apathy, perceptual problems/hallucinations, attention/memory, gastrointestinal, urinary, sexual dysfunction, and miscellaneous). It is scored by the clinician.
In contrast the Nonmotor Symptom Questionnaire(NMS-Quest) is self-administered and scored. It is a useful tool but is less sensitive at screening for apathy, olfactory dysfunction and somnolence.
The Parkinson’s Disease Questionnaire (PDQ-39) is a reliable tool for assessing quality of life in Parkinson’s patients. It is simple to complete and asks patients to recall over the past month how many times they have experienced certain events classified in 8 discrete scales – mobility, activities of daily living, emotional well-being, stigma, social supports, cognition, communication and bodily discomfort. A shorter version, PDQ-8, contains one question from each scale and is a reliable, quick measure of health-related quality of life in the patient being screened.
In addition to those discussed there are a number of other scales that have been developed in an effort to standardize the assessment of Parkinson’s disease symptoms and their impact on the patient’s quality of life. Although helpful in research and clinical practice they are not optimal and cannot substitute for the ultimate goal – to find a true marker of this disease.