FUNCAP provides an accurate and reliable assessment of how well a person can carry out different tasks. The patient-led approach to its development resulted in this assessment being based on the consequence of undertaking certain activities, rather than asking what tasks an individual can complete and how often.

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) affects an estimated 400,000 people in the UK but is probably underdiagnosed. It is characterised by post-exertional malaise, where activities lead to unusually long periods of recovery, and increases severity of other symptoms including extensive fatigue, brain fog, sensory hypersensitivity and sleep that fails to refresh.

ME/CFS also affects a person’s functional capacity, which is how well they are able to carry out day to day tasks, activities or work.

In the absence of diagnostic tests for ME/CFS, diagnosis requires clinicians to determine whether patients have a “significant reduction of their function capacity”. The fluctuating nature of ME/CFS can make this unreliable, especially around measuring functional capacity.

One major flaw in current tests for assessing functional capacity, especially in ME/CFS, is that they don’t consider post-exertional malaise. Two people with the same functional capacity for a certain task may have this assessed differently, depending on how they respond in a questionnaire. If you ask an ME/CFS patient if they “can” do an activity, one might answer that they “can” even if they will be hit by a prolonged increase in symptoms, while another might answer that they “can’t”, because they know they will experience a symptom increase. This makes the answers in current assessment tools difficult to interpret.

This problem also affects research into ME/CFS, as it makes it harder to measure whether a new treatment or way to manage symptoms is having a genuine effect in reducing the severity of the condition.

It’s a problem experienced by Professor Simon Carding and Dr Katharine Seton from the Quadram Institute, who have been designing clinical trials to understand the causes of ME and work towards effective treatments based on biomedical research, supported by the charity Invest in ME Research.

The lack of a reliable test for functional capability to measure outcomes was something that was being addressed in Norway. Norway has an excellent universal healthcare system and national guidelines for the accurate diagnosis and management of ME/CFS. Paediatric neurologist Kristian Sommerfelt from the University of Bergen, who has over thirty years of experience working with ME and Trude Schei from the Norwegian ME Association had also identified this gap in assessment measures and set about creating a better tool. Prof. Carding and Dr Seton were happy to join the team developing this further.

The team saw it as essential that they bring in the lived experiences of people with ME and their carers to develop a new functional capability test. Therefore, the first version of the new questionnaire was distributed amongst the Norwegian ME Association support groups, via social media, and through its reach 200 people with ME helped to test the first version of a new questionnaire designed by the team.

This identified a common problem of the questions not addressing the consequences of undertaking the activity, and how this then affected their capacity to perform other activities.

Respondents were encouraged to answer along with a family member or friend who knew them, as this improved the accuracy and overcame the problems of recall associated with brain fog.

Feedback

After the initial round of feedback, the team altered the questionnaire to introduce a seven-point response scale to better pick up these consequences of activities, and their duration.

For the second round of feedback, the questionnaire was left open for a longer period to allow time for the most severely-affected patients to take part and provide feedback.

The third version was used in clinical practice by Kristian Sommerfelt and other clinicians with extensive experience of diagnosing and working with people with ME.

For the fourth round of feedback, the questionnaire was translated into English and opened up to people with ME world-wide, so that its accuracy could be compared with a completely different group of people.

Final rounds of testing showed the high reliability and validity of the test by including healthy people, usually friends or family of people with ME, and asking the same respondents to repeat the test two weeks later.

FUNCAP – a new tool for measuring functional capacity

The resulting questionnaire for assessing functional capacity in ME/CFS patients is called FUNCAP and is now freely available online at in Norwegian, English, French, Dutch, German and Swedish. Japanese and Italian translations are underway.

It assesses functional capacity overall, and subdivided by activity domains, such as basic hygiene, walking, communication and concentration.

The researchers hope that FUNCAP will be a valuable tool to improve the diagnosis of ME/CFS, and better measure its impact on peoples’ lives, alongside other established tests for other aspects of the condition.

A shortened version of the questionnaire has also been made available for researchers to use in clinical trials of interventions and therapies to better analyse how these alter functional capacity.

Although designed with and for people with ME, FUNCAP could also contribute to studies of functional capacity linked to long COVID, where post-exertional malaise is increasingly being recognised as a symptom.

To find out more about FUNCAP visit the FUNCAP website

Reference: Sommerfelt, K., Schei, T., Seton, K. A., & Carding, S. R. (2024). Assessing Functional Capacity in Myalgic Encephalopathy/Chronic Fatigue Syndrome: A Patient-Informed Questionnaire. Journal of Clinical Medicine, 13(12), 3486. DOI: 10.3390/jcm13123486