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Table of Contents
ORIGINAL ARTICLE
Year : 2021  |  Volume : 39  |  Issue : 1  |  Page : 13-18

Reliability and validity of the Chinese version of the vitiligo specific quality of life instrument (VitiQoL)


1 Department of Dermatology, Shandong Provincial Hospital for Skin Diseases & Shandong Provincial Institute of Dermatology and Veneorology, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan; Department of Dermatology, Dalian Children's Hospital, Dalian, China
2 Department of Dermatology, Shandong Provincial Hospital for Skin Diseases & Shandong Provincial Institute of Dermatology and Veneorology, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, China
3 Department of Dermatology, Jinan Municipal Second Dermatosis Prevention and Control Hospital, Jinan, China
4 Department of Dermatology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA

Date of Submission01-Apr-2020
Date of Decision14-Aug-2020
Date of Acceptance22-Sep-2020
Date of Web Publication18-Feb-2021

Correspondence Address:
Dr. Baoqi Yang
Shandong Provincial Hospital for Skin Diseases & Shandong Provincial Institute of Dermatology and Veneorology, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, Shandong, 250022
China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ds.ds_48_20

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  Abstract 


Background: Vitiligo is an acquired, idiopathic skin disorder that can significantly affect the health-related quality of life (QoL). The vitiligo-specific QoL instrument (VitiQoL), recently developed by an American group, was found to be a reliable patient-reported outcome measure in both Brazilian and Iranian patients. Methods: The VitiQoL was initially cross-culturally adapted to Chinese through forward-backward translation. The Chinese version of the VitiQoL was then distributed to 182 vitiligo patients together with the dermatology life quality index (DLQI) and Skindex-16 questionnaire. Then, the reliability and validity of the Chinese version of the VitiQoL was assessed by statistical analysis. Results: The Chinese version of the VitiQoL showed high internal consistency (Cronbach alpha = 0.958) and test–retest reliability (intraclass correlation coefficient = 0.887). Convergent validity testing showed that the correlation coefficient for the Chinese VitiQoL and DLQI was 0.70 (P < 0.01), the Chinese VitiQoL and Skindex-16 each was 0.84 (P < 0.01), and for the Chinese VitiQoL (questions 1–15 and 16) was 0.62 (P < 0.01). Confirmatory factor analysis revealed two important factors within the VitiQoL: Participation limitation and stigma. Conclusion: The Chinese version of the VitiQoL questionnaire has sufficient reliability and validity to be used to evaluate Chinese vitiligo patients' QoL.

Keywords: Quality of life, vitiligo, vitiligo-specific quality of life instrument, reliability, validity


How to cite this article:
Zhao H, Zhao N, Zhou B, Chen G, Wang Y, Zhang H, Lin Y, Liu H, Kundu RV, Yang B. Reliability and validity of the Chinese version of the vitiligo specific quality of life instrument (VitiQoL). Dermatol Sin 2021;39:13-8

How to cite this URL:
Zhao H, Zhao N, Zhou B, Chen G, Wang Y, Zhang H, Lin Y, Liu H, Kundu RV, Yang B. Reliability and validity of the Chinese version of the vitiligo specific quality of life instrument (VitiQoL). Dermatol Sin [serial online] 2021 [cited 2021 Jun 18];39:13-8. Available from: https://www.dermsinica.org/text.asp?2021/39/1/13/309662

The authors, Hui Zhao and Na Zhao contributed equally to this work





  Introduction Top


Vitiligo is an acquired, idiopathic skin disorder characterized by circumscribed depigmented macules and patches. The etiopathogenesis of vitiligo is not clear, possibly involving genetic factors, autoimmunity, intrinsic defects of melanocytes and T-cells, and oxidative stress.[1],[2],[3] It is estimated that 0.5%–2% of the general worldwide population is affected by vitiligo. People of different ethnicities, skin types, and sex appear to be equally affected. Onset is most commonly observed from age 10–30, with the average age of onset being 20 years.[4],[5]

Unlike other skin disorders, vitiligo lesions are typically asymptomatic, which means that the patients do not feel pain or pruritus, and the condition has no effect on patients' longevity. Hence, the aim of vitiligo treatment is to improve skin appearance, requiring a long time, usually 6–18 months.[6] The long treatment cycles and lack of pigment often cause problems for patients, having major impacts on their health-related quality of life (QoL). Indeed, many studies have documented the significant effects of vitiligo on the QoL, and many instruments have been used to assess it, including validated generic and dermatological, health-related QoL scales.[7],[8],[9],[10]

Currently, the dermatology life quality index (DLQI) and the Skindex-16[11] are the most reported measures used to evaluate the QoL of vitiligo patients, and some studies using these instruments show that these patients have a significant decrease in QoL.[12],[13],[14]

Recently, a disease-specific instrument, the vitiligo-specific QoL instrument (VitiQoL) questionnaire was developed by an American group.[15] The VitiQoL is a questionnaire of 15 items, with item scores from 0 (never) to 6 (all the time). It yields a total score of from 0 to 90. Moreover, it presents a personal assessment of the severity of the vitiligo, using a scale ranging from 0 (no skin involvement) to 6 (worst case), which corresponds to the 16th question of the VitiQoL questionnaire and do not count in the total score. Meanwhile, they found that the VitiQoL is more sensitive than the DLQI in terms of discriminant validity.

The VitiQoL was found to be a reliable patient-reported outcome measure in both Brazilian and Iranian patients with satisfactory internal consistency (Cronbach's alpha, 0.944 and 0.956, respectively) and test–retest reliability (intraclass correlation coefficient [ICC],0.95 and 0.914, respectively).[16],[17] At the same time, there was a significant correlation between VitiQoL and DLQI (r = 0.776, P < 0.001); also between VitiQoL and subjects' assessment of the severity of their disease.[15] In this study, we aimed to perform the translation, cross-cultural adaptation and validation of the VitiQoL into Chinese, and evaluate its reliability in Chinese-speaking patients with vitiligo.


  Materials and Methods Top


Translation

First, we obtained permission from the holder of the original English version of the VitiQoL. Then two bilingual physicians translated it into Chinese. After that, the Chinese version of VitiQoL was translated back into English by a certified language service provider with no access to the original English questionnaire (back-to-back translation). Afterward, the final version was compared with the original English version. Finally, five dermatologists reviewed the Chinese translation and reached consensus.

To test the questionnaire, we recruited 10 vitiligo patients to complete it, asking them whether there was anything they could not understand, collecting their answers, and asking them how they determined their answers. Based on their feedback, we revised several words in the questionnaire to conform with Chinese language and culture. After determining that there were no misunderstandings, the final Chinese version of the VitiQoL questionnaire was administered for the study [Figure 1].{Figure 1}

Recruitment of participants

Vitiligo patients were recruited from two hospitals. Patient inclusion criteria: At least 18 years of age, a confirmed diagnosis of Vitiligo by a dermatologist, able to read and understand Chinese. Exclusion criteria: Patients with concomitant dermatological disease.

According to the literature reviewed,[18] the sample size should be 5 to10 times the number of questions in the questionnaire. Considering that vitiligo is a common disease and to compensate for probable dropouts, our aim was to recruit about 200 participants.

All the patients recruited in this study were outpatients. We asked each participant to complete the Chinese version of the VitiQoL, the DLQI, and the Skindex-16, according to the corresponding requirements of the questionnaire. All patients were asked to complete these three questionnaires twice, day 0 and day 7. They were permitted to take home the documents, finish them on day 7 at home, and return them to the researcher by either letter or messaging app WeChat.

Statistical analysis

All statistical analysis was performed using SPSS software (SPSS Inc., Chicago, IL, USA). P < 0.05 was considered statistically significant.

Reliability

Reliability refers to the extent to which a variable can be demonstrated to be measured in a reproducible fashion, or the extent to which the results measuring a stable variable can be relied on to be the same on each subsequent administration. The reliability of the instrument was demonstrated through the analysis of internal consistency using Cronbach's coefficient of reliability. Test–retest reliability was assessed by comparing the total VitiQoL scores in a subset of patients who completed the questionnaire twice. The patients were asked to finish the second questionnaire within a week, at least no > 2 weeks. The ICC was calculated to determine the ability of the tool to give concordant results at different times, and we used the “single measurement” to calculate the ICC.

Validity

A test is valid if it measures what it purports to measure. There are a variety of ways to demonstrate the validity of a test. Validation of the Chinese version of VitiQoL includes assessing content, construct, convergent, and discriminant validity. With content validity, one is most concerned with the extent to which all facets of a construct are represented within an instrument. In practice, content validity is ensured by having experts in the field evaluate an item pool to determine whether it represents an accurate and comprehensive coverage of the construct. Construct validity is assessed through exploratory factor analysis, which is performed to assess the dimensionality of the 15 items and to validate the structure of the Chinese version of the VitiQoL. Convergent validity is determined by correlating the VitiQoL scores with the scores obtained from the DLQI and Skindex-16. Discriminant validity is assessed by comparing the proportions of insensitive items in the VitiQoL and DLQI (or VitiQoL and Skindex-16).

Ethics approval and consent to participate

The study was conducted in accordance with the Declaration of Helsinki. The protocol was approved by the Ethics Committee of Shandong Provicial Hospital for Skin Diseases (2017-007). All participants signed the written consent form.


  Results Top


Demographics

We excluded some unqualified questionnaires, such as those incompletely filled out or having unrecognizable handwriting. Finally, we selected 182 qualified questionnaires from the total of 200. A total of 182 patients with vitiligo were recruited between October 2017 and June 2018, and 102 patients (56.04%) finished the second questionnaire after 1 week (no >2 weeks). Of the 182 patients recruited, 98 were men and 84 were women. Patient age ranged from 18 to 74 years, with a mean age of 31.30 years. The number of school years completed ranged from 6 to 19, with a mean of 13.85 years. Duration of the disease ranged from 0.08 to 60 years, with a mean of 4.04 years. Patient demographics are presented in [Table 1] and the descriptive statistics of the outcome measures are presented in [Supplementary Material 1].{Table 1}[INLINE:1]

Reliability and validity

The translated VitiQoL showed high internal consistency (Cronbach alpha = 0.958). Item total correlation ranged between 0.54 and 0.87. The correlations also showed high test–retest reliability, with an ICC of 0.887; the ICC of each item is presented in [Table 2].{Table 2}

With regard to convergent validity, the correlation coefficient for the Chinese VitiQoL and DLQI was 0.70 (P < 0.01), for the Chinese VitiQoL and Skindex-16 it was 0.84 (P < 0.01), and that for the Chinese VitiQoL (questions 1–15) and VitiQoL (question 16) was 0.62 (P < 0.01). There was no significant difference in the proportion of insensitive items between VitiQoL and DLQI (Pearson's Chi-square test, P = 0.076), or between the VitiQoL and Skindex-16 (Fisher exact test, P = 0.608). Statistical analyses of reliability and validity measures are presented in [Table 3].{Table 3}

Factor analysis

The Kaiser–Meyer-Olkin measure of sampling adequacy (0.935) and the Bartlett test of sphericity (P < 0.05) showed that factor analysis of the data was appropriate.[19] The Cattell scree plot suggested that two factors (participation limitation and stigma) should be retained, representing 66.32% of the cumulative variance. Exploratory factor analysis and principal component analysis followed by Oblimin rotation with Kaiser normalization, which displays that 11 items were loaded on the participation limitation subscale (questions 3–9, 11–14); four items were loaded on the stigma subscale (questions 1, 2, 10, and 15). The two dimensions represented are shown in [Table 4].{Table 4}


  Discussion Top


Descriptive statistics

As we can see from [Supplementary Material 1], the single item that most contributed to the total score of VitiQoL was related to disease progression (question 15); other items that significantly contributed to the final scores were concern over skin appearance (question 1) and frustration about skin condition (question 2). The average value of all the patients' items is 27.75, indicating that vitiligo has a significant impact on the patient's QOL. Meanwhile, the items that significantly contributed to the total score of DLQI and Skindex-16 was also related to the emotional dimension, such as feeling embarrassed or depressed, which reflected on the consistency with VitiQoL.

Reliability

To the best of our knowledge, the VitiQoL is the first specific assessment tool related to vitiligo. In our study, we established a Chinese version of a VitiQoL questionnaire, then performed reliability and validity tests. The reliability of the Chinese version was confirmed by Cronbach's alpha (0.958), which is a little higher than the original VitiQoL Cronbach's alpha (0.935) and similar to the Brazilian/Portuguese and Iranian/Persian study (Cronbach's alpha, 0.944 and 0.956, respectively). A Cronbach's alpha of >0.7 is considered an ideal score with which to evaluate the reliability of patient-reported measures for internal consistency of a questionnaire.[20] Therefore, the Chinese version of VitiQoL should be a suitable measure for evaluating the QoL of Chinese vitiligo patients. In the original VitiQoL, one of the authors' limitations was the fact that no assessment of test-retest reliability had been carried out. In our study, 102 patients (56.04%) completed the VitiQoL twice, confirming the ICC of 0.887, which was a little lower than the values found in the Brazilian/Portuguese study (ICC, 0.95). However, it is worth mentioning that in our study, the sample size for test–retest reliability was larger than that in the Brazilian/Portuguese study (16 subjects, 21% of the sample). Thus, the data suggest that the Chinese VitiQoL will yield consistent results under similar conditions.

Validity

In this study, we selected DLQI and Skindex-16 as the calibration questionnaires based on literature review. With respect to convergent validity measures, we recognize that 0.61–0.80 are considered good correlation values and excellent when they are >0.81.[21] We revealed good convergence between VitiQoL and DLQI (r = 0.701, P < 0.01), and excellent convergence between VitiQoL and Skindex-16 (r = 0.843, P < 0.01). This result was similar to that of the original study (DLQI: r = 0.832; Skindex-16: r = 0.816). With respect to discriminant validity, there was no significant difference in the proportion of insensitive items between VItiQoL and DLQI (P = 0.076), or between VitiQoL and Skindex-16 (P = 0.608). However, we cannot find the data for discriminant validity either in the original study or in the subsequent verification study. We believe that the cultural difference can be explained by the insensitivity of the result.

Factor analysis

In the original VitiQoL study, the questionnaires were classified as factors of three categories: Participation limitation (questions 3, 4, 6, 9–11, and 14), stigma (1, 2, 5, 7, and 15), and behaviors (8, 12, and 13). However, in our study, the questionnaires were classified as factors of two categories: Participation limitation (questions 3–9, 11–14) and stigma (questions 1, 2, 10, and 15). There are some differences between our study and the original study, such as question 10 (“Has your skin condition affected your emotional well-being?”) belonging to a participation limitation factor in the original study, whereas in our study, this item belongs to the stigma factor, because in the Chinese, “emotional well-being” is more easily affected by some stigma factors such as being worried about the disease progressing to new areas.

Meanwhile, questions 8 (“Has your skin condition influenced the clothes you wear?”), 12 (“Has your skin condition affected your grooming practices?”), and 13 (“Has your skin condition affected your sun protection efforts during recreation?”) belong to behaviors in the original study, but also belong to participation limitation in our study. That may be because among the Chinese, patients with vitiligo can only wear long sleeves to cover their “white spots” or protect their skin even in summer. In addition, they must spend a long time on sun protection efforts such as using sun cream every day, which is a limitation to them. The last differences are concerning questions 5 (“When you were talking to someone, have you worried about what they may be thinking of you?”) and 7 (“Have you felt embarrassed or self-conscious because of your skin?”). These questions belong to the stigma category in the original study, but they also belong to participation limitation in our study, meaning that Chinese patients may avoid communicating with other people because they are afraid of embarrassment or what others think about them, which to them is a limitation.

Limitations

There are some limitations in our study. First, the study was performed in only two hospitals, which may not be representative of all vitiligo patients in society. Second, the mean age in our study was younger than in the original study because some older people had a low level of education and did not understand our questionnaire very well. This factor may have caused age bias.


  Conclusions Top


This Chinese version of the VitiQoL questionnaire has adequate validity and reliability for our study. It can be used in Chinese patients to evaluate the QoL of patients with vitiligo.

Acknowledgments

The authors are grateful to all participants and assessors for their contributions.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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