Background

The objective of this summary is to outline the history of the development and the validation of a health index for patients with axial spondyloarthritis (axSpA) based on the International Classification of Functioning, Disability and Health (ICF) as a use case.

The burden of disease in axial spondyloarthritis (axSpA) is for the majority of patients considerable. Even after intensive discussions within Assessment of SpondyloArthritis international Society (ASAS) no agreement had been reached to define the severity of axSpA. The impact of disease on functioning is an essential information for clinicians when reporting health problems of individual patients. The ICF is a comprehensive and universally accepted model to classify and describe functioning, disability and health in a systematic way. Based on the ICF, a core set of items for axSpA was selected to represent the entire spectrum of possible problems in functioning. The ICF emphasizes health results from complex interactions of impairments, limitations and restrictions caused by the disease and various contextual factors. One major ICF Innovation is the identification and classification of these contextual factors that address the role of environmental and personal factors on functioning and health. Environmental factors (EF) are defined as the physical, social and attitudinal environment in which people live and conduct their lives.

ASAS decided in 2009 to develop a disease specific patient-reported outcome assessing global functioning and health (also called heath related quality of life) in axSpA patients, the ASAS Health Index (ASAS HI). Since environmental context has impact on how an individual will remain active and participate in society, ASAS decided upfront to develop an Environmental contextual factors (EF) Item Set (EFIS) accompanying the ASAS HI.

Aim

The aim of this ASAS-project was (I) to develop and validate the ASAS HI to quantify global functioning in patients with axSpA, and (II) to develop the EFIS accompanying the ASAS HI.

Methodology

A         ASAS Health Index

The questionnaire was developed and validated in three main steps:

Step 1: Development of the ASAS Health Index as patient-reported outcome based on the ICF (in English). Therefore, this international study was conducted in English speaking countries.  The different phases of development are shown in table 1.

Table 1: Phases of development for the ASAS Health Index and the EF item set

Step 2: Translation: Translation and cross-cultural adaptation of the ASAS HI were performed according to published recommendations. This was undertaken in 5 stages: translation, synthesis of translation, back translation, expert committee review and pre-testing in a field test.

Step 3: Validation and investigation of psychometric properties: The international validation study aimed to include 50-100 patients per country (sample size depends on the country size). All axSpA patients underwent a baseline part. Stable patients could enter the reliability part (at least 25% of the total sample size) and patients who need a therapeutic change could enter the part of sensitivity to change (another minimum of 25% of the total sample size). To assess construct validity, predefined hypothesis on level of correlation of other measurement domains with of the ASAS HI were tested using Spearman correlation with several standard health outcomes for axSpA. Test–retest reliability was assessed by intraclass correlation coefficients (ICCs) in patients with stable disease (interval 4–7 days). In patients who required an escalation of therapy because of high disease activity, responsiveness was tested after 2–24 weeks using standardised response mean (SRM). This study was also internationally conducted in English and in non-English speaking countries.

B         Environmental contextual factors (EF) Item Set (EFIS)

The EFIS development paralleled the ASAS HI development, following the same six phases as of the ASAS HI.

Table 2: Phases of development for the EF Item Set (EFIS)

The main difference of the ASAS HI development was that in phase I patients did not weigh the importance of items representing the environmental contextual factors. All subsequent phases were conducted in parallel and in the same countries of the ASAS HI development throughout the whole process.

Results:

A         ASAS Health Index

Step 1 Development: The ASAS HI is a linear composite measure and includes 17 items (dichotomous response option: “I agree” and “I do not agree”) which cover most of the ICF core set. A wide range of ICF categories are assessed including pain, emotional functions, sleep, sexual functions, mobility, self-care, and community life.

Step 2 Translation: The ASAS HI were translated into Arabic, Chinese, Croatian, Dutch, French, German, Greek, Hungarian, Italian, Korean, Portuguese, Russian, Spanish, Thai and Turkish in an international study. Translation and cross-cultural adaptation of the ASAS HI into 15 languages in 23 countries showing good performance in different cultures in patients with axSpA. Between 2013 and 2020 the ASAS HI was translated in 14 additional languages (Bulgarian, Czech, Danish, Estonian, Finish, Hebrew, Japanese, Latvian, Lithuanian, Norwegian, Polish, Romanian, Swedish, Taiwanese).

https://www.asas-group.org/instruments/asas-health-index/

Step 3 Validation: Construct validity ranged from low (age: 0.10) to high (Bath Ankylosing Spondylitis Functional Index (BASFI): 0.71). Internal consistency was high (Cronbach’s α of 0.93). The reliability among 578 patients was good (ICC=0.87 (95% CI 0.84 to 0.89)). Responsiveness among 246 patients was moderate-large (SRM=−0.44 for non-steroidal anti-inflammatory drugs (NSAIDs), −0.69 for conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) and −0.85 for tumour necrosis factor inhibitor (TNFi). The smallest detectable change was 3.0. Values ≤ 5.0 have balanced specificity to distinguish good health as opposed to moderate health, and values ≥ 12.0 are specific to represent poor health as opposed to moderate health.

B         Environmental contextual factors (EF) Item Set (EFIS)

Step 1 Development

Fifty-three items related to one of the EF categories of the WHO/ASAS Core Set for AS were found in 24 different questionnaires, none of them commonly used in patients with SpA. These items could be linked to 7 of the 13 EF categories of the ICF Core Set for SpA. As final result of item selection process 9 items were included in the EFIS. Decision was based on the extent of the correlation coefficient between each individual EF item and the sum score of the ASAS HI as well as considering avoidance of redundancy because of high correlation coefficient individual items of EFIS and ASAS HI total sum and coverage of representative domains of the Comprehensive ICF Core Set for AS.

Step 2: Translation

The EFIS were translated into 15 languages (Arabic, Chinese, Croatian, Dutch, French, German, Greek, Hungarian, Italian, Korean, Portuguese, Russian, Spanish, Thai and Turkish) Between 2013 and 2020 the ASAS HI was translated in 4 additional languages: Danish, Romanian, Swedish and Taiwanese.

Conclusions:

Functioning and health in patients with axSpA can be assessed in clinical trials and in daily routine by using one of the disease-specific ASAS HI versions covering most of the languages worldwide. ASAS HI proven to be valid, reliable and responsive. The ASAS HI can be used to evaluate the impact of SpA and its treatment on functioning and health. An EFIS is available complementing the ASAS HI and helps to interpret the ASAS HI results by gaining an understanding of the interaction between a health condition and contextual factors. The EFIS emphasizes the importance of support and relationships, as well as attitudes of the patient and health services in relation to self-reported health

Timelines of the project: 2009 – 2020

Project Team

PI: Juergen Braun (Herne, Germany)

Steering committee: D. van der Heijde (Leiden, Netherlands), A. Boonen (Maastricht, Netherlands), Uta Kiltz (Herne, Germany)

Working group: Akkoc, N. (Turkey), W Bautista-Molano (Bogota, Colombia), R Burgos-Vargas (Mexico City, Mexico), P Chiowchanwisawakit (Bangkok, Thailand), A. Cieza (Genive, Switzerland), Dougados, M. (Paris, France), T Duruoz (Turkey), B El-Zorkany (Cairo, Egypt), I Essers (Maastricht, Netherlnads), I Gaydukova (St. Petersburg, Russia), P Géher (Budapest, Hungary), Gensler, L. S. (San Francisco, USA), Gilio, M.(Italy), L Gossec (Paris, France), S Grazio (Zagreb, Croatia), J Gu (China), Inman, R. D. (Canada), M. A. Khan (USA), T J Kim (South Corea), W. P. Maksymowych (Egmonton, Canada) , H. Marzo-Ortega (Leeds, UK), V Navarro-Compán (Madrid, Spain), I Olivieri (ITaly), Ozgocmen, S. (Turkey), D Patrikos (Greece), F M Pimentel-Santos (Lissabon, Portugal), J. Reveille (Houston, USA), M Schirmer (Innsbruck, Austria), S. Stebbings (New Zealand), G. Stucki (Switzerland), F van den Bosch (Ghent, Belgium), van Tubergen, A. (Maastricht, Netherlands),  U Weber (Switzerland), Wei, J. C. (Taiwan),  J Zochling (Austraia).

Publications

1. Kiltz U, van der Heijde D, Cieza A, Boonen A, Stucki G, Ustun B, et al. Developing and validating an index for measuring health in patients with ankylosing spondylitis. Rheumatology (Oxford). 2011 May; 50(5):894-898.
2. Kiltz U, van der Heijde D, Boonen A, Cieza A, Stucki G, Khan MA, et al. Development of a health index in patients with ankylosing spondylitis (ASAS HI): final result of a global initiative based on the ICF guided by ASAS. Ann Rheum Dis 2015;74:830-5
3. Kiltz U, van der Heijde D, Boonen A, Bautista-Molano W, Burgos-Vargas R, Chiowchanwisawakit P, et al. Measuring impairments of functioning and health in patients with axial spondyloarthritis by using the ASAS Health Index and the Environmental Item Set: translation and cross-cultural adaptation into 15 languages. RMD Open. 2016; 2(2):e000311.
4. Kiltz U, van der Heijde D, Boonen A, Akkoc N, Bautista-Molano W, Burgos-Vargas R, et al. Measurement properties of the ASAS Health Index: results of a global study in patients with axial and peripheral spondyloarthritis. Ann Rheum Dis. 2018 Sep; 77(9):1311-1317.
5. Kiltz U, Boonen A, van der Heijde D, Bautista-Molano W, Burgos Vargas R, Chiowchanwisawakit P, et al. Development of an environmental contextual factor item set relevant to global functioning and health in patients with axial spondyloarthritis. Rheumatology (Oxford). 2022 May 5; 61(5):2054-2062.