The construct validity, responsiveness, reliability and interpretability of the Recap of atopic eczema questionnaire (RECAP) in children.

BACKGROUND: The Recap of atopic eczema questionnaire (RECAP) was developed to measure eczema control in patients with atopic dermatitis (AD). The measurement properties of RECAP have not yet been validated in caregivers of children with AD. OBJECTIVES: To assess the construct validity, responsiveness, reliability and interpretability of the Dutch proxy version of RECAP. METHODS: A prospective validation study was conducted in children (aged < 12 years) with AD and their caregivers (in a Dutch tertiary hospital). At three timepoints (T0 = baseline; T1 = after 1-7 days; T2 = after 4-8 weeks) RECAP and multiple reference instruments were completed by caregivers of child patients. Single- and change-score validity (responsiveness) were tested with a priori hypotheses on correlations with reference instruments. Intraclass correlation coefficients (ICCagreement) and standard error of agreement (SEMagreement) were reported. Bands for perceived eczema control were proposed. The smallest detectable change (SDC) and minimally important change (MIC) were determined. Two anchor-based methods based on receiver operating characteristic curve (ROC) and predictive modelling were used to determine the MIC. RESULTS: A total of 231 children with AD and their caregivers participated. Of our a priori hypotheses for single-score and change-score validity, 77% and 80% were confirmed, respectively. A stronger correlation than hypothesized was found for all rejected hypotheses.Excellent reliability was found (ICCagreement = 0.94, 95% confidence interval 0.90-0.96). The SEMagreement was 1.9 points. The final banding was 0-1 (completely controlled), 2-7 (mostly controlled), 8-12 (moderately controlled), 13-18 (a little controlled) and 19-28 (not at all controlled). A cutoff point of ≥ 8 was selected to identify children whose AD is not under control. The SDC was 5.3 and the MIC values were 1.5 and 3.6 for the ROC and predictive modelling approaches, respectively. No floor or ceiling effects were observed. CONCLUSIONS: The proxy version of RECAP is a valid, reliable and responsive measurement instrument for measuring eczema control in children with AD. An improvement of ≥ 6 points can be regarded as a real and important change in children with AD.

Atopic dermatitis (AD) is a skin disease that affects children and adults. People with AD (eczema) and other stakeholders have identified perceived 'eczema control' as an important outcome to investigate in research. For this purpose, the Recap of atopic eczema (RECAP) questionnaire was developed, consisting of seven items to measure eczema control in people with AD. However, when developing questionnaires, they must be examined to ensure they are relevant, reliable and sensitive enough to detect meaningful change before and after any new treatment. Prior studies have demonstrated that the RECAP is suitable for adults with AD, but studies investigating whether the RECAP is suitable for children are lacking. A study of 231 children (under 12 years old) with AD and their caregivers was conducted in the Netherlands. Caregivers completed the RECAP questionnaire at three time points: at the start of the study, after 1­7 days and after 4­8 weeks. The researchers assessed AD severity and eczema control using other measures for comparison. RECAP scores from children whose caregivers reported unchanged eczema control were used to assess how reproducible this questionnaire was. RECAP scores of caregivers who reported change in eczema control were used to examine sensitivity to change. Statistical tests were used to analyse findings. The researchers found that RECAP accurately measures changes in eczema control over time and was sensitive enough to detect small changes in eczema control. Overall, the authors concluded that the RECAP questionnaire is valid, reproducible and responsive. Furthermore, they consider an improvement of at least 6 points to represent a genuine improvement in Dutch children.

Validity, reliability, responsiveness and interpretability of the Recap of atopic eczema (RECAP) questionnaire.

BACKGROUND: Limited research has been conducted on the measurement properties of the Recap of atopic eczema (RECAP) questionnaire, particularly in relation to interpretability. OBJECTIVES: To investigate the validity, reliability, responsiveness and interpretability of the Dutch RECAP in adults with atopic dermatitis (AD). METHODS: We conducted a prospective study in a Dutch tertiary hospital, recruiting adults with AD between June 2021 and December 2022. Patients completed the RECAP questionnaire, reference instruments and anchor questions at the following three timepoints: baseline, after 1-3 days and after 4-12 weeks. Hypotheses testing was used to investigate single-score validity and change-score validity (responsiveness). To assess reliability, both standard error of measurement (SEMagreement) and intraclass correlation coefficient (ICCagreement) were reported. To assess the interpretability of single scores, bands for eczema control were proposed. To investigate the interpretability of change scores, both smallest detectable change (SDC) and minimally important change (MIC) scores were determined. To estimate the MIC scores, four different anchor-based methods were employed: the mean change method, 95% limit cut-off point, receiver operating characteristic curve and predictive modelling. RESULTS: In total, 200 participants were included (57.5% male sex, mean age 38.5 years). Of the a priori hypotheses, 82% (single-score validity) and 59% (responsiveness) were confirmed. Known-group analyses showed differences in the RECAP scores between patient groups based on disease severity and impairment of the quality of life. The SEMagreement was 1.17 points and the ICCagreement was 0.988. The final banding was as follows: 0-1 (completely controlled); 2-5 (mostly controlled); 6-11 (moderately controlled); 12-19 (a little controlled); 20-28 (not at all controlled). Moreover, a single cut-off point of ≥ 6 was determined to identify patients whose AD is not under control. The SDC was 3.2 points, and the MIC value from the predictive modelling was 3.9 points. Neither floor nor ceiling effects were observed. CONCLUSIONS: The RECAP has good single-score validity, moderate responsiveness and excellent reliability. This study fills a gap in the interpretability of the RECAP. Our results indicate a threshold of ≥ 6 points to identify patients whose AD is 'not under control', while an improvement of ≥ 4 points represents a clinically important change. Given its endorsement by the Harmonising Outcome Measures for Eczema initiatives, the results of this study support the integration of RECAP into both routine clinical practice and research settings.

EDP-297: A novel, farnesoid X receptor agonist-Results of a phase I study in healthy subjects.

EDP-297 is a farnesoid X receptor agonist under development for treating nonalcoholic steatohepatitis. The pharmacokinetic (PK), pharmacodynamic (PD), food effect, and safety were evaluated in a single ascending dose (SAD) and multiple ascending dose (MAD) phase I study. Healthy subjects received single EDP-297 doses of 20-600 µg or once daily doses of 5-90 µg for 14 days. Safety, PKs, and PDs were assessed, including fibroblast growth factor 19 (FGF-19) and 7-α-hydroxy-4-cholesten-3-one (C4). Among 82 subjects, EDP-297 was generally well-tolerated. Pruritus was observed in four subjects in the SAD phase and seven subjects in the MAD phase; four severe cases occurred at 90 µg in the MAD phase, including one that led to drug discontinuation. A grade 2 elevation in alanine aminotransferase occurred with 90 µg. Mean lipid values remained within normal range. Plasma exposures of EDP-297 increased with SADs and MADs, with mean half-life following multiple doses of 9-12.5 h. No food effect was observed. Mean FGF-19 increased and C4 decreased up to 95% and 92%, respectively. EDP-297 was generally well-tolerated up to 60 µg MAD, with linear PKs suitable for once daily oral dosing, target engagement, and no food effect.

Content validity of the Recap of atopic eczema (RECAP) instrument in Dutch, English and German to measure eczema control in young people with atopic eczema: a cognitive interview study.

BACKGROUND: Recap of atopic eczema (RECAP) is a patient-reported outcome measure assessing eczema control. This instrument has been developed and validated in the UK. There are self-reported and proxy-reported versions in English, Dutch and German. However, it is unclear whether the self-reported version shows adequate content validity when completed by young people (8-16 years) in these languages. OBJECTIVES: To assess the content validity (comprehensibility, relevance and comprehensiveness) of the English, German and Dutch versions of the self-reported RECAP in young people with atopic eczema and to identify the most appropriate age cutoff for self-completion. METHODS: We conducted 23 semistructured cognitive interviews with young people aged 8-16 years, using the 'think-aloud' method. In Germany and the Netherlands, participants were recruited in dermatology clinics and in the UK through social media and existing mailing lists. Interviews were audio recorded, transcribed verbatim and analysed in the three languages, using a problem-focused coding manual. Transcripts were coded by two independent reviewers in each country. Themes were translated into English and compared across the three countries. RESULTS: Significant age-related comprehensibility issues with the last three items of the questionnaire occurred with young people aged 8-11 years, causing difficulties completing RECAP without help. However, older children had only minor problems and were able to complete the questionnaire by themselves. The self-reported version of RECAP has sufficient content validity for self-completion in young people aged 12 years and above. However, the German version with some translational adaptations may be appropriate for children from the age of 8 years. There may be some situations where the proxy version is needed for older children too. CONCLUSIONS: The self-reported version of RECAP is appropriate for use from the age of 12 years. The proxy version can be used in children younger than 12 years. Other measurement properties should be further investigated. What is already known about this topic? Recap of atopic eczema (RECAP) is an instrument recommended by the Harmonising Outcome Measures for Eczema initiative for the core outcome domain of long-term control of atopic eczema. Content validity of RECAP for self-completion by adults and of the proxy version has been assessed. What does this study add? In this study, content validity (comprehensibility, relevance and comprehensiveness) of the self-reported version of RECAP among young people (aged 8-16 years) with atopic eczema across the UK, Germany and the Netherlands is assessed. Based on these findings, key recommendations on how to measure eczema control in young people with atopic eczema are formulated. What are the clinical implications of this work? The Dutch, English and German self-completion versions of RECAP are recommended for use in adolescents from the age of 12 years. The proxy version could be used in children younger than 12 years or where children are cognitively or physically incapable of reporting their experience of eczema control. Caregivers should be encouraged to complete RECAP together with their child where possible.

Eczema control and treatment satisfaction in atopic dermatitis patients treated with dupilumab - a cross-sectional study from the BioDay registry.

BACKGROUND: Eczema control is a new construct to be measured in atopic dermatitis (AD). OBJECTIVES: Measuring patient-perceived eczema control and treatment satisfaction in AD patients, treated with dupilumab between 16 and 52 weeks. METHODS: Cross-sectional questionnaire study. Patients from the Dutch BioDay registry completed the Atopic Dermatitis Control Test (ADCT), Recap of Atopic Eczema (RECAP) and Treatment Satisfaction Questionnaire for Medication, Version II (TSQM v. II), along with other Patient Reported Outcome Measures (PROMs). RESULTS: 104/157 patients responded (response rate 66.2%). Median ADCT score was 4 (interquartile range [IQR] 5); median RECAP score was 5 (IQR 6); median TSQM v.II global satisfaction score was 83.3 (IQR 25.0). According to the ADCT, 38.5-66.3% perceived their AD was 'in control', depending on the interpretability method used. Minimally clinically important difference (MCID) of ≥4 points for the DLQI and POEM was achieved respectively in N = 66 (84.6%) and N = 63 (78.8%) patients. CONCLUSION: When considering the favorable scores on other PROMs and the TSQM v. II, and comparing these to the relatively low percentage of patients perceiving control according to the ADCT, interpretability of eczema control still appears difficult. Treatment satisfaction in the studied cohort was high.

Guidelines for diagnosis, prevention, and treatment of hand eczema.

BACKGROUND: Hand eczema is a common inflammatory skin disorder. Health care providers need continuously updated information about the management of hand eczema to ensure best treatment for their patients. OBJECTIVES: To update the European Society of Contact Dermatitis guideline on the diagnosis, prevention, and treatment on of hand eczema. METHOD: The Guideline Development Group (GDG) was established on behalf of the ESCD. A call for interest was launched via the ESCD website and via the ESCD members' mailing list. Appraisal of the evidence for therapeutic and preventive interventions was applied and a structured method of developing consensus was used and moderated by an external methodologist. The final guideline was approved by the ESCD executive committee and was in external review on the ESCD webpage for 1 month. RESULTS: Consensus was achieved for several statements and management strategies. CONCLUSION: The updated guideline should improve management of hand eczema.

Vesicular hand eczema transcriptome analysis provides insights into its pathophysiology.

Hand eczema is a common inflammatory skin condition of the hands whose pathogenesis is largely unknown. More insight and knowledge of the disease on a more fundamental level might lead to a better understanding of the biological processes involved, which could provide possible new treatment strategies. We aimed to profile the transcriptome of lesional palmar epidermal skin of patients suffering from vesicular hand eczema using RNA-sequencing. RNA-sequencing was performed to identify differentially expressed genes in lesional vs. non-lesional palmar epidermal skin from a group of patients with vesicular hand eczema compared to healthy controls. Comprehensive real-time quantitative PCR analyses and immunohistochemistry were used for validation of candidate genes and protein profiles for vesicular hand eczema. Overall, a significant and high expression of genes/proteins involved in keratinocyte host defense and inflammation was found in lesional skin. Furthermore, we detected several molecules, both up or downregulated in lesional skin, which are involved in epidermal differentiation. Immune signalling genes were found to be upregulated in lesional skin, albeit with relatively low expression levels. Non-lesional patient skin showed no significant differences compared to healthy control skin. Lesional vesicular hand eczema skin shows a distinct expression profile compared to non-lesional skin and healthy control skin. Notably, the overall results indicate a large overlap between vesicular hand eczema and earlier reported atopic dermatitis lesional transcriptome profiles, which suggests that treatments for atopic dermatitis could also be effective in (vesicular) hand eczema.

Interpretability of the Quality Of Life in Hand Eczema Questionnaire.

The Quality Of Life in Hand Eczema Questionnaire (QOLHEQ) is used to measure impairment of health-related quality of life in hand eczema. Here, we prospectively studied the interpretability of international QOLHEQ scores at three time points: baseline, after 1-3 days (T1), and after 4-12 weeks (T2). Adult patients with hand eczema completed the QOLHEQ and anchor questions for overall assessment of health-related quality of life impairment. Interpretability of single scores was assessed at baseline by defining severity bands based on agreement with the anchor questions. Smallest detectable change was calculated at T1. Minimally important change of improvement was calculated at T2 using three methods: mean cut-off, receiver operating characteristic, and 95% limit. A total of 294 adult patients were included (160 males, mean age 44.9 years). The final proposed severity band of overall QOLHEQ single scores (κ-coefficient of agreement, 0.431) was not at all, 0-10; slightly, 11-39; moderately, 40-61; strongly, 62-86; and very strongly, ≥87. Separate overall severity bands were proposed for males and females and the four subscales of the QOLHEQ. The smallest detectable change in 166 unchanged patients was 18.6 points. The preferred minimally important change, obtained with the receiver operating characteristic method, was 21.5 points. An overall QOLHEQ score of ≥22 is recommended as cut-off for a minimally important, real change.

Effect of dupilumab on hand eczema in patients with atopic dermatitis: An observational study.

Systemic treatment options for chronic hand eczema are limited. Dupilumab is used in atopic dermatitis (AD) but is not licensed for (isolated) hand eczema. In this observational prospective study we aimed to determine the response of hand eczema to dupilumab in patients with AD. Adult patients with hand eczema and AD received dupilumab s.c. at a 600 mg loading dose, followed by 300 mg every 2 weeks. Primary outcome was a minimum improvement of 75% on the Hand Eczema Severity Index after 16 weeks (HECSI-75). Secondary outcomes were severity, measured using the Photographic guide; quality of life improvement as patient-reported outcome, measured using the Dermatology Life Quality Index (DLQI); and AD severity, measured using the Eczema Area and Severity Index (EASI). Forty-seven patients were included (32 males; mean age, 45 years). HECSI-75 was achieved by 28 (60%). Mean HECSI score reduction was 49.2 points (range, 0-164; 95% within-subject confidence interval, 46.4-52.0), which was already significantly decreased after 4 weeks (P < 0.001). DLQI score mean improvement was 8.8 points (standard deviation [SD], 6.0) or 70.0% decrease (SD, 26.4) (P < 0.001). Eighteen patients (38%) were classified as responders on the Photographic guide. There was no difference in response between chronic fissured and recurrent vesicular clinical subtypes. Similar percentages of patients achieving EASI-75 and HECSI-75 were seen after 16 weeks. In conclusion, this study shows a favorable response of hand eczema to dupilumab in patients with AD. This raises the question whether a response will also be seen in isolated hand eczema.

[Ocular symptoms associated with dupilumab in atopic dermatitis]. / Oogklachten door dupilumab bij constitutioneel eczeem.

BACKGROUND: Dupilumab, the first registered biological for the treatment of atopic dermatitis, frequently causes adverse ocular events. These often take the form of mild conjunctivitis or blepharoconjunctivitis, however, more serious adverse ocular events have also been reported, including limbal stem cell insufficiency. CASE DESCRIPTION: A 56-year-old man was treated with dupilumab for severe atopic dermatitis. His eczema improved greatly, but he developed bilateral conjunctivitis with limbal stem cell insufficiency in his right eye. After discontinuation of dupilumab, the eye symptoms gradually disappeared. After three months no conjunctivitis or limbal stem cell insufficiency was observed on ophthalmological examination. CONCLUSION: Adverse ocular events are often seen in the treatment of atopic dermatitis with dupilumab. Caution is advised if severe adverse events occur. Therefore, it is important to identify the underlying pathophysiological mechanism of these adverse events.

Hand eczema among Dutch beekeepers - a cross-sectional study.

BACKGROUND AND OBJECTIVES: Studies of beekeepers have mostly focused on contact allergy to propolis. The overall prevalence of hand eczema (HE) in beekeepers has not been studied. Our objectives were to gain insight into the prevalence of HE in the Dutch beekeeper population; to define the impact of beekeeping activities on HE and vice versa; and to determine associated factors. PATIENTS AND METHODS: We used a cross-sectional online survey. Dutch beekeepers answered questions on beekeeping activities, the prevalence and characteristics of HE, including severity, and the impact of the disease on beekeeping. RESULTS: We analyzed 833 surveys (12 % of Dutch beekeepers). The one-year prevalence of HE was 13.2 %, and the lifetime prevalence was 20.5 %. In 28 patch-tested beekeepers with hand eczema, eight (28.6 %) were allergic to propolis. Atopic dermatitis was the only variable associated with HE: the odds ratio was 4.53 (95 % confidence interval 2.78-7.38). One in three beekeepers reported that HE was caused or worsened by beekeeping, although only 3.8 % reported working less at beekeeping because of HE, and the impact of HE on beekeeping activities (as perceived by beekeepers) is low. CONCLUSIONS: In this sample of Dutch beekeepers, hand eczema was more prevalent than in the general population, but seems to have had little impact on the beekeeping activities of the majority of beekeepers.

Which outcomes have been measured in hand eczema trials? A systematic review.

The considerable heterogeneity of outcomes and measurement instruments in hand eczema trials substantially limits the evidence synthesis concerning therapeutic and preventive interventions. Therefore, the Hand Eczema Core Outcome Set (HECOS) initiative is developing a core outcome set for future trials. The first objective was to identify outcomes that were measured in previous trials, to group them in domains, and to identify their measurement instruments. We conducted a systematic review of controlled and randomized controlled hand eczema trials published since 2000. Sixty-one eligible studies were identified. Each assessed one or more of 47 outcomes in the "skin" domain. Eighteen trials (30%) additionally focused on preventive behaviour in risk occupations. Quality of life was measured in 13 studies (21%). Thirty-two distinct named instruments were applied, but 223 measurements (62%) were conducted with unnamed instruments. Only 32 studies (52%) defined a primary outcome. Twenty-nine trials (48%) provided some information on adverse events, but none gave any references concerning relevant methods. Our review confirms the need to harmonize outcome measurements in hand eczema trials. The findings form the basis for a consensus process to generate a core outcome set to improve the explanatory power and comparability of future hand eczema studies.

European Surveillance System on Contact Allergies (ESSCA): Contact allergies in relation to body sites in patients with allergic contact dermatitis.

BACKGROUND: Analyses of the European Surveillance System on Contact Allergies (ESSCA) database have focused primarily on the prevalence of contact allergies to the European baseline series, both overall and in subgroups of patients. However, affected body sites have hitherto not been addressed. OBJECTIVE: To determine the prevalence of contact allergies for distinct body sites in patients with allergic contact dermatitis (ACD). METHODS: Analysis of data collected by the ESSCA (www.essca-dc.org) in consecutively patch tested patients, from 2009 to 2014, in eight European countries was performed. Cases were selected on the basis of the presence of minimally one positive patch test reaction to the baseline series, and a final diagnosis of ACD attributed to only one body site. RESULTS: Six thousand two hundred and fifty-five cases were analysed. The head and hand were the most common single sites that ACD was attributed to. Differences between countries were seen for several body sites. Nickel, fragrance mix I, cobalt and methylchloroisothiazolinone/methylisothiazolinone were the most frequent allergens reported for various body sites. CONCLUSIONS: Distinct allergen patterns per body site were observed. However, contact allergies were probably not always relevant for the dermatitis that patients presented with. The possibility of linking positive patch test reactions to relevance, along with affected body sites, should be a useful addition to patch test documentation systems.

Study protocol: efficacy of oral alitretinoin versus oral cyclosporine A in patients with severe recurrent vesicular hand eczema (ALICsA): a randomised prospective open-label trial with blinded outcome assessment.

INTRODUCTION: Systemic treatment with alitretinoin is registered for all clinical types of severe chronic hand eczema. However, it is especially effective in the hyperkeratotic subtype and less effective in non-hyperkeratotic forms. Cyclosporine A (cyclosporine) is prescribed for hand eczema in daily practice as well. It has shown to be particularly effective in patients with vesicular hand eczema. The primary objective of this study is to compare efficacy of alitretinoin and cyclosporine in the treatment of severe recurrent vesicular hand eczema. METHODS AND ANALYSIS: This is an investigator-initiated randomised prospective open-label trial with blinded outcome assessment. Severity assessments and laboratory measurements will be conducted corresponding to daily practice. The study population will consist of 72 adult patients (age 18-75 years) with severe recurrent vesicular hand eczema. Patients are treated with either (group I) alitretinoin 30 mg once daily or (group II) cyclosporine with a starting dose of 5 mg/kg/day and a decrease in dosage after 8 weeks to 3-3.5 mg/kg/day. The treatment period is 24 weeks for both drugs. Primary endpoint for efficacy is response to treatment, defined as an improvement of ≥2 steps on a Physician Global Assessment, using a validated Photoguide, after 24 weeks of treatment. Secondary endpoints are improvement of Hand Eczema Severity Index, Quality of Life in Hand Eczema Questionnaire and a Patient Global Assessment. Adverse events and time to response will be registered. Furthermore, cost-utility, quality-adjusted life years and cost-effectiveness will be assessed with the EQ-5D-5L questionnaire while monitoring costs. ETHICS AND DISSEMINATION: This protocol was reviewed and approved by the Medical Ethical Review Board of the University Medical Centre Groningen (reference METc 2015/375). The study will be conducted according to the principles of the Declaration of Helsinki, in accordance with the Dutch Medical Research Involving Human Subjects Act. TRIAL REGISTRATION NUMBER: NCT03026946; Pre-results.

Presenteeism in a Dutch hand eczema population-a cross-sectional survey.

BACKGROUND: Presenteeism (attending work despite complaints and ill health, which should prompt rest and absence) has been overlooked in the field of hand eczema. OBJECTIVES: To examine the 1-year prevalence of presenteeism related to hand eczema in a population of hand eczema patients who visited a tertiary referral centre. Secondary objectives: to identify intrinsic/extrinsic reasons for presenteeism and to evaluate associated factors. METHODS: This was a cross-sectional questionnaire study. Presenteeism was defined as "going to work despite feeling you should have taken sick leave because of hand eczema". Respondents answered questions about socio-demographic factors, clinical features, occupational characteristics, and hand eczema related to occupational exposure. RESULTS: Forty-one per cent (141/346) of patients who had both worked and had hand eczema during the past 12 months reported presenteeism. The most often reported reasons were: "Because I do not want to give in to my impairment/weakness" (46%) and "Because I enjoy my work" (40%). Presenteeism was associated with: mean hand eczema severity; absenteeism because of hand eczema; improvement of hand eczema when away from work; and high-risk occupations. CONCLUSIONS: In this study, presenteeism was common and predominantly observed in patients with more severe hand eczema and occupational exposure. The most frequently reported reasons for presenteeism were of an intrinsic nature.

Guideline for translation and national validation of the Quality of Life in Hand Eczema Questionnaire (QOLHEQ).

There is a need for well-developed and validated questionnaires to measure patient reported outcomes. The Quality of Life in Hand Eczema Questionnaire (QOLHEQ) is such a validated instrument measuring disease-specific health-related quality of life in hand eczema patients. A re-validation of measurement properties is required before an instrument is used in a new population. With the objective of arriving at a guideline for translation and national validation of the QOLHEQ, we have developed the design of a reference study on how to adequately assess measurement properties of the QOLHEQ based on interdisciplinary discussions and current standards. We present a step-by-step guideline to assess translation (including cross-cultural adaptation), scale structure, validity, reproducibility, responsiveness, and interpretability. We describe which outcomes should be reported for each measurement property, and give advice on how to calculate these. It is also specified which sample size is needed, how to deal with missing data, and which cutoff values should be applied for the measurement properties assessed during the validation process. In conclusion, this guideline, presenting a reference validation study for the QOLHEQ, creates the possibility to harmonize the national validation of the various language versions of the QOLHEQ.