Validation of the Specificity of the Bells Test for Progressive Supranuclear Palsy

Progressive Supranuclear Palsy (PSP) is a rare and incurable neurodegenerative disease that affects ~7 in 100,000 people. People with PSP can have many of the same symptoms as people with Parkinson’s disease and their first diagnosis is often Parkinson's disease (PD). On average, it takes about 3 years for a patient to get their correct PSP diagnosis. This delay creates uncertainty for patients and restricts their ability to access appropriate support. Patients also require many additional hospital visits which is costly and burdensome for them and the NHS. Delayed diagnosis is also challenging for developing new treatments, because researchers cannot be certain which patients have PSP. Patient groups and doctors agree that research into new tools that address the challenge of early and accurate differential diagnosis of PSP and PD should be a high priority. One important difference between PSP and Parkinson's disease is that PSP affects cognitive function early in the disease. PSP patients have often problems with attention, short term memory and planning. Our previous research has shown that people with PSP have particular problems with visual attention, for example when they are trying to find an object that is hidden among distractors (e.g. a ‘Where’s Wally’ type of puzzle). People with Parkinson’s disease do not have this problem. The ability to search for a target among distractors can be measured scientifically using a test called the Bells Test, which test measures how quickly and accurately a person can find and circle bell-shaped objects hidden among other objects. This test is usually used to screen stroke patients for attention problems, but in a recent trial funded by the Vivensa foundation we discovered that people with PSP perform very poorly on this test compared to people with PD. In fact, the Bells test was able to discriminate between people with PSP and PD with specificity of .96. A test with high specificity is particularly useful for rare diseases, as it allows doctors to rule out the most common alternative diagnoses, in this case PD. The aim of this project is to validate the specificity of the Bells test in a new group of 5 people with PSP and 52 people with Parkinson's. Feedback from patients and carers emphasised the importance of accessibility and minimising travel, so our project was designed with the NIHR RRDN as a community based project. RRDN Agile researchers will conduct the tests during a home visit or e-appointment via video-conference. Each participant will be tested twice, once within 4 weeks of enrolling and again after 6 months, which will also allow us to track how their performance changes over time. Faster and more accurate diagnosis of PSP will reduce the costs of multiple hospital visits for carers and the NHS, give certainty to patients and carers, help ensure patients have access to appropriate care pathways and can be a key enabler of trials of new drugs to treat PSP. The Bells test is non-invasive, quick, free and easy to score, so is very economical in terms of financial cost and clinician time. It already widely used in stroke medicine so barriers to adoption are low, and our team includes clinicians who specialise in Parkinson’s disease education for healthcare professionals, so are ideally placed to ensure doctors hear about and use the findings of this research.