Validation of a Brief ICF Core Set for COPD from the Perspective of Multidisciplinary Experts: A Delphi Study

To validity the Brief International Classification of Function, Disability, and Health Core Set from the perspective of multidisciplinary experts in China in order to apply it to global function assessment for Chinese patients with Chronic Obstructive Pulmonary Disease (COPD). Twenty-one experts who engaged in COPD clinical treatment or nursing, clinical rehabilitation therapy, chronic disease management, and clinical psychology research for more than 10 years’ experience were selected for the two rounds of Delphi consultations. Six out of 21 participants (28.6%) were males, and the average age was 48.19 (6.32) years old. The average length of working years was 24.95 (7.63) years. The authority coefficients for two rounds of Delphi consultation were both 0.836, and Kendall’s coordination coefficients were 0.215 and 0.344, respectively. The average importance value of indexes ranged from 3.52 to 4.90. The Brief ICF-COPD Core Set in Chinese version consisted of 4 firstlevel and 14 second-level categories finally, which is scientific and rational, which can be applied as a simple and standardized tool in multidisciplinary rehabilitation strategy for implementation and evaluation of follow-up.


Introduction
Chronic Obstructive Pulmonary Disease (COPD) is not only characterized by progressive deterioration of pulmonary function, but also leads to restrictions in daily activities and societal participation, worse quality of life, and psychological problems, including anxiety and depression [1].In China, COPD is the third leading cause of death, [2] and the most recent epidemiology survey shows that the prevalence among individuals aged above 40 years old is 13.7% [3] as compared with a global prevalence of 11.7% [4]. Pulmonary rehabilitation, which is recognized as a core component in the management of COPD, [5,6] offers an integrated approach for personalized management of patients with COPD through thorough assessment of treatable traits [7]. Although pulmonary rehabilitation has been clearly shown to improve exercise capacity and quality of life, the lack of consistent standards to evaluate the effects remains a global challenge [8]. Therefore, an effective specific assessment instrument which could evaluate patients' global functioning should be developed.
The World Health Organization International Classification of Function, Disability, and Health (ICF) provides an international standard and global agreed-on language for description and measurement of function limitation and rehabilitation in a unified view of various dimensions of health [9]. The ICF is composed of Volume  Functioning & Disability covers Body functions (b), Body structure (s), and Activities and participation (d). Contextual factors consist of environment factors (e), which encompasses physical, social, and attitudinal categories, and personal factors that include gender, age, educational level, and so on. Personal factors with various categories are not included in the current ICF version. Body function and structure domains describe the impairment of anatomical and physiological function of different body systems [10]. The activity and participation domain refers to the limitation or difficulty an individual experiences to perform a particular task in a certain environment and restrictions to participate in life situation and interact with society. The contextual factors involving environmental and personal factors are linked to the first three domains [11].
Rehabilitation intervention for patients with COPD should be conducted according to ICF framework in order to improve communication among all individuals who could be involved in the development of a multidisciplinary rehabilitation strategy, such as patients, families, health professionals, researchers, and policy-makers. To facilitate the implementation of the ICF into clinical application in rehabilitation of patients with COPD, ICF Core Sets for obstructive pulmonary disease containing COPD and asthma have been developed, and two types of comprehensive and brief core set are involved [12]. The brief core set is composed by minimum data to be used in clinical practice [13]. The ICF-OPD Core Set was developed from COPD and asthma which differed with age, risk factors, disease trajectory, and treatment strategy [10]. Therefore, usage of the ICF-OPD Core Set for patients with COPD is not feasible, which contributed to the development of a specific ICF-COPD Core Set to guide health professionals to provide rehabilitation intervention. Huang only applied the Brief ICF-OPD Core Set in Chinese patients with COPD to test its validation directly, and the results showed that one category was not confirmed, while the other eight categories were not considered in the Brief ICF-OPD Core Set. However, lack of perspectives in Brief ICF-OPD Core Set from health professionals can lead to difficulty implementing it in clinical practice [14]. Therefore, the objective of this study was to validate the brief ICF-COPD Core Set from the perspective of multidisciplinary experts in China in order to apply it to global function assessment for Chinese patients with COPD.

Construct ICF Categories
To construct a preliminary category system for the Delphi questionnaire, we applied brief ICF-OPD Core Sets, which include four first-level categories and 14 second-level categories. There are four second-level categories in the body function component: respiration function (b440), additional respiratory function (b450), exercise tolerance functions (b455), and sensations associated with cardiovascular and respiratory function (b460). Two secondlevel categories consist of structure of cardiovascular system (s410), and structure of respiratory system (s430) in the body structure component. Four second-level categories involving carrying out daily routine (d230), walking (d450), moving around (d455), and doing housework (d640) are included in the activity and participation component. The environmental component consists of products and substances for personal consumption (e110), products and technology for personal use in daily living (e115), climate (e225), and air quality (e260). After this process, a preliminary Delphi questionnaire was completed. The flowchart of the study process is shown (Figure 1). The study protocol was approved by the local ethics committee of Tianjin Medical University, China. The structure of this paper was assessed by SQUIRE reporting guidelines [15].

Selection of Delphi Experts
Twenty-one experts were selected for the Delphi consultations. The selection criteria were as follows: professional level and engaged in COPD clinical treatment or nursing, clinical rehabilitation treatment, chronic disease management and clinical psychology research for more than 10 years' experience, and consent to participate in the study. The characteristics of the experts are summarized in Additional File 1.

Delphi Consultation Process
Two rounds of Delphi consultation were conducted. The questionnaire was sent to the experts by e-mail after receiving their permission. Experts rated each of the first-level and secondlevel categories based on the level of perceived importance, rated from 1 (least important) to 5 (most important) (Additional File 2). Experts also defined the basis of their judgment according to their views in practical experience, theoretical knowledge, literature review, and intuitive feeling, and expert's judgment criteria for the categories was between 0.1 and 0.5 (Additional File 2). The degree of familiarity with each of the categories was rated from 0 to 1 (Additional File 2). The results of each consultation round were assessed for completeness, and experts were also contacted if there were any omissions or unclear content. The results of the first-round consultation were analyzed and explained and were also provided to experts when the second-round questionnaire was delivered. Tables   Level of Importance  Score   Very important  5   Important  4 Moderately important 3

Additional File 2: The Value
Unimportant 2 Most unimportant 1

Inclusion and Exclusion of the Categories
When analyzing the results of the first round of expert consultations, it was possible to add new categories on the basis of outcomes of the consultation process. After the second consultation round, the inclusion criteria of the results were mean of the importance score≥3.5, Coefficient of Variation (CV) <0.25 [16]. At the same time, the implications, significance, and data availability of each category should be fully considered to screen and construct the Brief ICF-COPD Core Set system.

Statistical Analysis
All the questionnaire data were double entered. Data analysis was performed using Microsoft Excel 2013 (Microsoft Corporation, Redmond, Washington, USA) and SPSS 25.0 software (IBM Corporation, New York, USA). The expert authority coefficient was calculated according to the following formula: Cr= (Ca+Cs)/2. Ca refers to the expert's judgment criteria for the categories, and Cs refers to the familiarity degree for the categories. The importance score was represented by mean and standard deviation (SD). Consensus and coordination of experts were calculated by coefficient of variation (CV) and the Kendall's coefficient of concordance (Kendall's W). P<0.05 in the Kendall's W were the criteria for consensus in the study.

Basic Information of Experts
A total of 21 experts participated in the consultation, among whom 28.6% were males (6/21) and 71.4% were females (15/21). The experts ranged in age from 36 to 55 years, with an average age of 48.19 (6.32) years old. The number of years working in COPD management ranged from 10 to 32 years, with an average length of 24.95 (7.63) years. With respect to academic level of expertise, 61.9% (13/21) were professionals, and 38.1% (8/21) were associate professionals. All of the experts were from tertiary hospitals and research institutions, including Beijing, Tianjin, and Guangzhou in China. Their major disciplines included clinical treatment, pulmonary rehabilitation, clinical nursing, psychological therapy, Chinese traditional therapy, and respiratory disease research of COPD.

Expert's Authority Coefficient
In two rounds, 21 questionnaires were issued and recovered with a recovery rate of 100%. Generally, the expert's authority coefficient greater than 0.7 was in an acceptable range [17].the authority coefficients for two rounds of Delphi consultation were both 0.836. This showed that the experts in this study had a high level of familiarity with the categories, including research and practical work in COPD. Therefore, the selection of categories and the results had high credibility [18].

Degree of expert coordination
Kendall's coordination coefficients (W) refers to whether there are big differences between experts in their opinions on an evaluation of each index. W is between 0 and 1, with a greater value, indicating a higher degree of concordance between experts. In two rounds of consultation, Kendall's coordination coefficients were 0.215 and 0.344, respectively (P<0.001) (

Validation of the Brief ICF-COPD Core Set Framework
The Brief ICF-COPD Core Set framework was validated after the second round of Delphi consultation. This was comprised of four first-level and 14 second-level categories (Table 5). For the first-level indexes, Body functions (b), Body structure (s), Activities and participation (d), and Environment factors (e), the index weights were 4.71, 4.57, 4.30, and 4.25, respectively. For the second-level indexes, the index weight was from 3.52-4.90, and the index weight of three top second-level indexes were Respiratory function (b440), Structure of respiratory system (s430) and Structure of cardiovascular system (s410), respectively.

Discussion
This study was the first to employ a Delphi technique to identify a Brief ICF-COPD Core Set, which was based on the ICF-OPD published by the World Health Organization (WHO) [19]. This study contributes to the current knowledge on the development of a multidisciplinary rehabilitation strategy as our findings reveal a high consensus among clinical experts regarding the most relevant and common categories of functioning in management of COPD. By linking all responses, it could be shown that the Brief ICF-COPD Core Set with 14 categories is a valid tool to evaluate patients' global functioning in China.
The study recruited 21 multidisciplinary experts, including physicians, nurses, rehabilitation specialists, and psychologists, experienced in the management of COPD from three cities in China, which can extend the field of expertise and represent more experts' advice [20]. Within all of the participants, 14 (66.7%) have a master's or doctoral degree, and all of them (100%) were professionals; meanwhile, 15 (71.4%) have more than 20 years experiences of management in COPD, which shows that the experts have deeper understanding of this subject that conforms to the screening conditions of the Delphi technique [17]. Effective recovery two-round surveys were both 100%, and the expert's authority coefficient were both 0.836, which showed that the experts in this study had a high level of familiarity with the categories and the selection of categories, and the results had high credibility [18]. After two rounds of expert surveys, the importance of the first-level indexes were 4.25-4.71, CV 0.09-0.18, and Kendall coordination coefficient 0.199. Meanwhile, the importance of the second-level indexes were 3.52-4.90, CV 0.06-0.26, and Kendall coordination coefficient 0.358. All of the results showed the good reliability of ICF-COPD [20]. cardiovascular and respiratory function (b460), can represent common function problems in patients with COPD. Respiratory function (b440) refers to the function of taking air into the lungs, exchanging it with the blood, and exhaling it, such as respiratory rate, rhythm, and depth function. Additional respiratory functions (b450) refers to the auxiliary function related to breathing, such as coughing, sneezing, and yawning. Exercise tolerance function (b455) refers to functions related to respiratory and cardiovascular capacity as required for enduring physical exertion. Sensations associated with cardiovascular and respiratory function (b460) refers to arrhythmia, palpitations, shortness of breath, and other feelings. Respiratory muscle dysfunction, including inspiratory muscle impairment and expiratory muscle fatigue, is the major disorder in patients with COPD [21]. Approximately 10% of the patients with COPD from the Copenhagen General Population Study suffered from chronic cough and demonstrated lower lung function, more symptoms (including wheezing, dyspnea, and chest tightness) [22]. Ischemic heart disease, atrial fibrillation, and heart failure are also coexisting conditions in patients with COPD [23].
Body structure includes structure of cardiovascular system (s410) and structure of respiratory system (s430). Pathological changes in the characteristics of COPD are found in the airways, lung parenchyma, and pulmonary vasculature [24].Chronic inflammation is the main pathological change, which induces parenchymal tissue destruction and disruption of normal repair and defense mechanisms in patients who develop COPD. Cardiovascular diseases are common and important comorbidities in patients with COPD due to left ventricular dysfunction [25].
Activities and participation include Carrying out daily routine (d230), Walking (d450), Moving around (d455), and Doing housework (d640). Carrying out daily routine (d230) refers to scheduling, planning, organizing, and completing some simple or complex coordinated activities. Walking (d450) refers to walking on the ground step by step, such as walking, pacing, forward, back, or sideways. Moving around (d455) refers to moving the body from one place to another other than walking, such as rock climbing, jumping, running, jogging and swimming. Doing housework (d640) refers to managing the home by cleaning the house, doing laundry, using appliances, storing food, and tiding up. The physical activity of patients with COPD, such as cleaning, working, and exercising, is substantially less than that of healthy persons of the same age and sex [26]. The GOLD guideline states that all patients with COPD could benefit from regular physical activity [27]. Physical activity was impaired early in the process of the disease with COPD, [28] which influences the patients' ability to perform and participate in activities. Generally, the attenuation of lower-limb and upper-limb endurance are present at the same time for patients with COPD, [30,31] and respiratory and muscle dysfunction leads to fatigue and a reduction in physical activity [29]. Environment factors involve e110 Products or substances for personal consumption, e115 Products and technology for personal use in daily living, e225 Climate, and e260 Air quality. Products or substances for personal consumption (e110) refers to any natural or human-made object or substance gathered, processed or manufactured for ingestion, such as food, drink, and drugs. Products and technology for personal use in daily living (e115) refers to equipment, products and technologies used by people in daily activities, including those adapted or specially designed, located in, on, or near the person using them. Climate (e225) refers to meteorological features and events, such as the weather. Air quality (e260) refers to characteristics of the atmosphere (outside buildings) or enclosed areas of air (inside buildings), and which may provide useful or distracting information about the world. Malnutrition with weight loss due to increasing energy expenditure and insufficient dietary intake is very common in patients with COPD, [31] and pharmacological therapy is the necessary treatment for patients in stable COPD [27]. Therefore, patients require the use of surrounding environmental equipment to acquire sufficient food and drugs. COPD is associated with exposure to tobacco smoke and other environmental substances, such as biomass fuel, and potential occupational irritants [32,33]. Cold weather is also a risk factor heightening the mortality [34].
However, there are some limitations regarding the external validity of this study. Firstly, experts in different disciplines were chosen through their published articles related to ICF or COPD in China. Due to a new perspective in ICF used in COPD, some participants have a lack knowledge of ICF even though they self-reported an expert's authority coefficient. Secondly, although the authors were successful in recruiting 21 experts from different professions, the participants consisted predominantly of physicians in clinical treatment, with a lack of experts who were skilled in rehabilitation of COPD, which led to limits of the generalizability of clinical practice. To minimize these, we chose more experienced and knowledgeable experts in management of COPD who mastered the comprehensive rehabilitation of COPD.

Conclusions
The Brief ICF-COPD Core Set assessment index system is scientific and rational. Thus, it can be applied as a simple and useful tool in a multidisciplinary rehabilitation strategy within multi-professional teams. Based on the Brief ICF Core Set for COPD, the impairment in body functions and structures, limitations in activities, restrictions in participation and the influences in environmental factors can be described and measured in a standardized way in China, which can also be used as a reference for implementation and evaluation of followup since the management of COPD requires longitudinal care involving multidisciplinary health professionals. Further research is necessary regarding the feasibility of the Brief ICF-COPD in