If Sustainable Developmental Goal 3 and Universal Health Coverage are to be achieved, functioning is a third health indicator which must be assessed and integrated into global health population-based metrics alongside mortality and morbidity. In this paper, we define functioning according to the International Classification of Functioning, Disability and Health (ICF) and present why functioning is important to measure, especially when considering the need for, and outcome of, rehabilitation and assistive technology (AT). We discuss examples of tools that measure components of functioning through clinical assessment and self-report methodologies, and present the development of a comprehensive population level tool which aligns with the ICF and combines self-report and clinical measurement methods to measure functioning and the need for rehabilitation and AT. Throughout the paper a survivor of Coronavirus 2019 (COVID-19) is given as an example to illustrate functioning according to the ICF and how access to the interventions of rehabilitation and AT might be of benefit to improve and optimise his/her functioning. We argue that the Global Health community must take action and ensure that the measurement of functioning is well established, accepted and integrated as the third health indicator following the COVID-19 pandemic.
Keywords: Functioning; population measurement; global health; rehabilitation; assistive technology
Responsible Editor Maria Nilsson
Historically population-based metrics in Global Health have relied heavily on mortality and morbidity. These two health indicators have accumulated great importance and are used widely when assessing health within nations and populations. Though gaps still remain, mortality and morbidity data have led to the development of life-saving health interventions and are increasingly routinely measured in health systems. Morbidity is defined as having a disease or the amount of disease in a population, but what about the Global Health metrics after morbidity? As members of a population survive with health conditions, including communicable or non-communicable diseases, what indicator is available to measure their lived experiences of health throughout the life course?
The importance of these questions can be illustrated through the coronavirus disease 2019 (COVID-19). Though much is still unknown about COVID-19 and the recovery trajectory, it is increasingly clear that many COVID-19 survivors experience difficulties in functioning following both hospitalisation for severe acute disease and recovery from mild to moderate symptoms in home/community settings. Evidence suggests high physical, neuropsychological and social need, and that the most common post-COVID symptoms are fatigue, breathlessness and psychological distress, including depression, anxiety and PTSD [[
An essential complementary third health indicator, functioning, provides metrics about how people are living in their daily lives [[
DIAGRAM: Figure 1. Example of International Classification of Functioning, Health and Disability (ICF) diagram for health condition of coronavirus disease 2019 (COVID-19) with access to related service and assistive technology needs [[
Figure 1(b) presents an example of functioning, using the ICF framework, as applied to a hypothetical COVID-19 survivor. In this example, a COVID-19 survivor experiences a mobility impairment due to high levels of fatigue and breathlessness resulting in poor endurance. He/she might experience difficulty walking long distances (activity restriction) preventing the survivor from getting to his/her office job (participation restriction) in the context of a long-distance commute involving both walking and public transport (environmental factor). These difficulties may also result in psychological distress (personal factor) which in turn may further limit participation in work.
Functioning data are vital to understand the experiences of people with disabilities, older people and people living with chronic health conditions, non-communicable diseases, and communicable diseases with long term conditions, including COVID-19 survivors. More broadly, functioning is critical as the Global Health community aims to achieve Sustainable Development Goal (SDG) 3 'Ensure healthy lives and promote well-being for all at all ages' and Universal Health Coverage (UHC) [[
These factors have become even more important given changing global health and demographic trends, and the increased numbers of people experiencing functional difficulties and disability [[
Rehabilitation and assistive technology (AT) are two inter-related sectors that rely on functional assessment to identify appropriate interventions to optimise functioning and independence. Comprehensive data on functioning at the population-level are key for identifying need/unmet need for rehabilitation and AT. However, as both sectors advance their global agendas, these data are lacking in many areas of the world, constraining the effective planning and provision of these services [[
Given the importance of data on functioning, how can it be measured?
As summarised in Table 1, different methods are used to assess functioning, and/or rehabilitation or AT needs at the population-level (e.g. through surveys). However, most of them capture only one or a sub-set of the six ICF components.
Table 1. Examples of four tools that measure components of the International Classification of Functioning, Health and Disability (ICF) [[
Measurement tool example Tool method Number of ICF component/s Specific ICF component/s measured Description RAAB [ Clinical measurement 1 Impairment Objectively measures distance and near visual impairment (VI) and assesses cause. RAAB 7 integrates Peek acuity which assesses visual acuity by a non-specialist using a smartphone. Washington Group on Disability question sets [ Self-report 1 Activity limitations WHO Model Disability Survey [ Self-report 6 Health condition; body function; activity limitations; participation restrictions; environment and personal factors Self-reported questionnaire that asks people what they do, or do not do, in their daily lives focusing on functioning in multiple domains well-aligned with the ICF and a series of questions regarding domain-specific and participation-specific health service, rehabilitation and AT use. WHO GATE's rapid Assistive Technology Assessment [ Self-report 3 Activity limitations; participation restrictions; environment Self-reported questionnaire that assesses participants' need, unmet need and access to AT using adapted Washington Group Short Set as initial screening and images alongside each assistive product.
Two of the most commonly used approaches are clinical measurement and self-report; however, they produce inconsistent results and typically remain siloed, and do not provide holistic cross-ICF component measurement [[
Self-reported functioning measures are cheaper and easier to administer than clinical measures. The Washington Group on Disability question sets ask about difficulty completing activities, such as the Short set which focuses upon activities in six domains (seeing, hearing, walking, remembering, understanding and self-care) alongside select AT use [[
Returning to the COVID-19 example, identifying long term effects, such as vocal cord damage from invasive ventilator use, and associated functional difficulties with COVID-19 and its variants will require functional screening and measurement tools across multiple domains at both individual and population levels. It also will be important to ensure disaggregation of these data by key characteristics, such as age, race, ethnicity, gender, disability and other socio-demographic variables as well as qualitative methods to explore lived experience in more depth. Further, managing functional needs will require i) person-centred care; ii) a continuum of care from clinicians to community workers, and; iii) uptake of referrals to rehabilitation and AT interventions from acute to community health settings either virtually or face-to face [[
The 'Post-COVID-19 Functional Status (PCFS) Scale' is a self-report screening tool designed for telephone administration to assess the spectrum of functional outcomes following COVID-19 and track progress over time [[
A gap remains for a comprehensive tool, not just specific to COVID-19, which can be used at the population level to measure functioning and the need for rehabilitation and AT. In the AT2030 research funded by UK Aid, a functional needs assessment tool is being developed and tested which combines self-report and clinical measurement methods incorporating all ICF components [[
As the world grapples to 'build back better' following the COVID-19 pandemic and at the same time advance the SDG and UHC agendas, it is important to remember the SDGs' tagline 'leave no one behind'. To do this it is essential to ensure that the measurement of functioning is well established, accepted and integrated as the third health indicator. Increased attention is needed to ensure improved clarity, consistency and understanding of its definition and measurement. Development and application of population-based assessment tools which incorporate all components of the ICF will be important for generating comprehensive and comparable data on functioning needed to inform rehabilitation and AT, as well as other interventions/services. To action this, the Global Health community is encouraged to lead a shift of terminology and mindset from focusing on 'mortality' and 'morbidity' to equally include 'functioning.' This resultant scaling up of the measurement of functioning will enable us to inclusively build back better, improving health and wellbeing for all.
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No potential conflict of interest was reported by the authors.
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Alongside mortality and morbidity, functioning is a third health indicator which must be assessed and integrated into global health population-based metrics. This paper defines functioning, presents measurement options and highlights the importance of functioning when considering the need for, and outcome of, rehabilitation and assistive technology following a health condition illustrated by the example of COVID-19. Increased attention is needed to ensure improved clarity, consistency and understanding of the definition and measurement of functioning.
Correction Statement
This article has been republished with minor changes. These changes do not impact the academic content of the article.
By Dorothy Boggs; Sarah Polack; Hannah Kuper and Allen Foster
Reported by Author; Author; Author; Author
All authors were involved in the conceptualisation, drafting and final approval of the manuscript.