Quality of life in Hidradenitis Suppurativa (Acne Inversa): A scoping review

Abstract Background Hidradenitis Suppurativa (HS) is a chronic, relapsing, inflammatory skin condition which is physically, psychologically and socially disabling and often affects a patient's quality of life (QOL). There are numerous QOL tools used in dermatology. However, assessment of QOL in patients with HS is difficult due to the inability of generic QOL tools to specifically capture QOL in patients with HS. Numerous HS‐specific QOL tools have been developed in recent years. It is important to identify evidence on full psychometric evaluation of these tools. Objectives There has been a gradual increase in the use of generic and disease‐specific QOL tools in the last few decades. The aim of this scoping review (SR) is to evaluate the most widely used generic QOL tools and HS‐specific QOL tools to identify the psychometric evaluation of such tools. Methods Design: An SR guided by Joanna Briggs Institute manual and Arskey O’Malley framework guidelines. Data extraction included the studies available on full psychometric evaluation of the most widely used dermatology generic QOL tools in HS and HS‐specific QOL tools. Results Ten papers were included in the review, eight papers demonstrated HS‐specific QOL assessment tools. The psychometric properties of these tools were underpinned by reliability, validity and sensitivity measurement. Six disease‐specific tools were identified in this SR. However, they all lack full psychometric evaluation. Conclusion This review indicates that an extensive research in the field of QOL tools for HS is much needed. It is crucial to develop user‐friendly and validate disease‐specific tools to measure the real impact of disease on patients QOL. QOL instruments can evaluate the impact on life of an HS patient, thus helping improve intervention and management of disease. There is a necessity for more research into existing HS‐specific QOL tools and they should be widely tested and fully validated.

with extreme pain, discharge and odour and therefore, can potentially lead to significant psychological impact and greatly affect quality of life (QOL). 5 HS has a considerable negative effect on the life quality of persons who are affected by the disease as compared to other patients with other chronic skin conditions. 6,7 Patients' disease burden includes intense pain, work disability and thus leading to overall poor QOL. QOL is a multidimensional construct, which can be measured in various ways. 6,7 There are various QOL tools used in dermatology which can provide more in-depth data. The principle of QOL tool is to identify the health state experienced by the subject by means of an appropriate questionnaire covering several different QOL-related dimensions. 8 Moreover, a global index (or several indices) is determined with calculations thus calculating QOL. The development of valid instruments to measure QOL in dermatology plays a vital role in assessing a patient and deciding on the treatment. 8 Over the past years, QOL in patients with dermatological conditions has been broadly documented and various dermatology-specific instruments have been described to measure this impact. 8 There are some common generic QOL tools that are widely used in dermatology to assess QOL in patients with skin diseases including HS. For example, Dermatology Quality of life Index (DLQI) which was the first dermatologyspecific generic QOL instrument and to date is the most commonly used. 9 However, generic or dermatological QOL measures may not capture changes in QOL particularly in HS. 5 It's extremely important to identify if HS-QOL tools are developed with psychometric properties such as reliability, validity and internal consistency measurements. 2

| Aims and objectives
The aim of this scoping review (SR) is to illuminate and describe the QOL tools used in HS patients, both general and specific, in terms of reliability, validity, sensitivity and internal consistency and to describe these psychometric properties to ensure changes in patients QOL are captured.

| METHODS
Research findings on the topic were summarized and disseminated, research gaps in the area were identified, recommendations for future research were made and the literature was mapped with relevance to time, location, source and origin. The methodology for this SR was guided by The Joanna Briggs Institute (JBI) guidelines 10 and the preferred reporting system or framework for SR PRISMAs which has adapted guidance from Arksey & O'Malley framework. 11,12 This SR research has been formulated using PCC (Population, Concept and Context) frame following a certain inclusion and exclusion criteria. Data extraction and synthesis were performed following the study selection using a template data extraction from JBI reviewer's manual ( Figure 1). 10 Data are charted in the form of a table including study details, characteristics and extraction results (Table 1). 2,3,[5][6][7]9,13,20 The review included identifying the research question, identifying relevant studies, study selection, charting the data and collating, summarizing and reporting the results. All the studies included in this SR are presented in the form of a Table (Table 1).

| RESULTS
Our literature search returned 550 articles after the removal of duplicates. Following title and abstract screening, 505 were deemed not related to QOL in HS and were excluded. Excluded studies included comparison articles with evaluation between more than one QOL tool, articles focussed on sexual health and disease severity, opinion articles and those unrelated to QOL tools. Five articles were duplicate, not originally  filed. Six were abstracts only. Five textbooks were excluded, 30 articles did not refer to QOL in HS and 40 articles were related to the treatment therapy in HS and improvement in QOL of patients with HS with different trials of medications. Eight articles were related to the paediatric population. Eighty-three articles in total were excluded. The remaining 45 articles were included. Following the full text review, five articles were excluded, and 10 articles were included in this SR.

| General description of included studies
Of 10 papers, three papers were published in the United Kingdom, three papers were published in Europe, two papers were published in the United States of America, and two in Canada. Studies and literature search were performed in the respective countries where they were published. The included papers are based on different types of studies. There were five mixed method studies, two quantitative studies with literature search, two qualitative studies with literature search and one longitudinal study.

| Data analysis of the studies included
Basra et al. 9 provide a comprehensive review of validation data and clinical results of DLQI between a period of 1994-2007, 13,20 identifying that DLQI has been used in 33 different skin conditions including HS. A detailed literature was conducted including 272 full text articles. Data concerning the development of DLQI from its development till 2007 were identified in terms of psychometric analysis. DLQI assessed in 12 different international studies using different correlation coefficients, ranged from 0.56 to 0.99 (with most studies showing values above 0.90, which is remarkably high. Internal consistency reliability of DLQI was assessed in 22 international studies using Cronbach's ɑlpha and ranged from 0.75 to 0.92. Study showed that DLQI has good responsiveness to change for most of the skin conditions (p < 0.0001); however, HS was not mentioned on list for sensitivity of DLQI. DLQI was used in a number of studies in parallel to other generic QOL instruments and showed good validity in terms of content and construct validity with a mean value of r = 0.58-0.78 and p < 0.0001). Overall, DLQI was found to be the most popular and most used generic QOL instrument in dermatology. However, an issue was raised regarding underrepresentation of emotional aspects of some skin conditions which are emotionally disabling, for example, HS. Although, wider ranges of dimensions are covered with generic measurement tools, many dimensions of HS in terms of QOL are not covered with DLQI. Therefore, HS-specific scale is important for further research and disease management of HS. Another study by Jorge et al. 21 indicates that DLQI exhibits adequate psychometric reliability and unidimensional structure for assessing QOL in Brazilian dermatology patients with Cronbach alpha result of 0.90 (Cl 95% 0.89-0.91), demonstrating that DLQI adequately assess the concrete discomforts of HS, however item performance varies in different sex and cultures and suffers from item bias which can be improved with disease-specific questions.
A study by Sisic et al. 14 developed an QOL instrument for HS (HS-QOL). Patient interviews and expert opinion were used to develop a conceptual framework for HS. An HS-QOL-v1 measure was developed and pilot testing was done by conducting patient interviews, which resulted in HS-QOL-v2. It is a 53-item questionnaire which is suitable for assessment of QOL in HS. According to the study, HS-QOL-v2 demonstrated content validity based on review of literature, concept elicitation interviews, item generation and cognitive interviews. The study indicated that psychometric validation is in process for evaluation of reliability, discriminant capacity and responsiveness. Mclellan et al. 15 looked at the validation of HS-QOL following their introduction of HS-QOL instrument in 2017, which had 53 items. Fifty-five adults with HS participated in the study. Participants completed 30-min online survey. All the subscales indicated excellent reliability (internal consistency) except support subscale, which showed adequate consistency as compared to DLQI and DASS-21 (Depression Anxiety Stress Scale) scores. It showed excellent validity as correlations with other measures were in expected direction. HS-QOL was reduced to 44 items resulting in 7 subscale questionnaires. However, the study was limited by sample size; less number of items may increase the internal coefficiency of the items. Although, it requires further refinement and validation, it is an excellent instrument to assess QOL in patients with HS due to its multidimensional design.
Kirby et al. 2 developed and validated another QOL instrument called Hidradenitis Suppurativa Quality of Life (HiSQOL) for clinical trial measurement of HSspecific HR-QOL (Health-Related Quality of Life). A qualitative method was adopted in stage 1 conducting patients' interviews, stage 2 involved cognitive debriefing interviews and observational study of 222 patients was conducted in stage 3 which resulted in item reduction, validation measurement and psychometric properties assessment. Observational study of 215 patients was conducted in stage 4, to confirm the psychometric structure of the new scale. This 17 item QOL scale (HiSQOL) demonstrated reliability and validity to measure HS-specific HR-QOL in clinical trials. It showed excellent internal consistency reliability including each of the three subscales. However, responsiveness of the tool remains pending needing further research. Limitation to this study was that it under included the patients from different races and cultural beliefs. Moreover, further studies need to be performed for Differential Item Functioning analyses.
HSBOD (Hidradenitis Suppurativa Burden of Disease) is another HS-specific QOL 2018 instrument developed in a mixed method study by Pinard et al. 16 It is a 19-item instrument which is self-administered 10 cm visual analog scale (VAS) and was developed to understand the overall burden of disease in HS patients. HSBOD demonstrated strong internal consistency and convergent validity when compared to nondisease-specific DLQI but lack the full psychometric analysis. The study is limited by small sample size and requires further studies to confirm selection of items, validity and reliability. Although, HSBOD yield good responses, it requires abstract thinking, which can be quite difficult for some patients due to the cultural background.
Another new disease-specific questionnaire was developed by Marron et al. 17 called HSQOL-24. The study performed preliminary validation on the tool which indicated adequate reliability and validity values of the tool. Aragones et al. 18 extended the psychometric evaluation of the tool at a later stage. The questionnaire was validated with a sample of 130 patients with HS. It is a first self-administered QOL instrument in Spanish to assess QOL in patients with HS. This study demonstrated excellent reliability (test-retest), internal consistency, validity and discriminative capacity of the instrument. The reliability study indicates strong internal accuracy and reproducibility with Cronbach's alpha of 0.920 (test) and 0.917 (retest). Intraclass correlation coefficient with DLQI and Skindex-29 of 0.698 Cl 95% (0.456-0.844) and 0.900 Cl 95% (0.801-0.951), respectively. 17,18 For its use, cut-off points were set, and the instrument was found to be prone to adjustment.
A study by Peris et al. 19 demonstrated the psychometric evaluation of a new HS-specific QOL tool known as HIDRAdisk. It is a VAS and composes 10 questions. Study demonstrated significant construct validity, excellent internal consistency reliability, good testretest reliability and good responsiveness to change. Therefore, a validated tool in Italian language that can improve management in HS. Although, it can be an effective QOL tool, limitation can be its need for translation into different foreign languages for different populations.
Thorlacius et al. 5 developed another HS-specific QOL tool called HiSQOL. A 23 item HS-specific QOL questionnaire was developed. Study proved HiSQOL as comprehensible, acceptable and feasible which will prove quite beneficial in future to assess QOL in patients with HS. HiSQOL awaits psychometric evaluation. Limitations to this study analysis involve potential cultural bias with respect to the questionnaire's monocultural growth. This is therefore a possible weakness found in most processes of questionnaire growth. Furthermore, the study shows there could be a potential selection bias. 5 Table 1 shows all the details/results extracted from included studies (in relation to the concept of the SR). Table 2 2,3,[5][6][7]9,13,20 shows the psychometric properties of all the QOL tools identified in the review.

| DISCUSSION
This review has identified few studies measuring the impact of HS on QOL. Although, there are currently a limited numbers of HS-specific QOL tools, they lack full