Abstract
Introduction:
The Children’s Dermatology Life Quality Index has been used to measure quality of life in studies of pediatric localized scleroderma, which suggested only modest effects on quality of life. However, the Children’s Dermatology Life Quality Index psychometric performance has not been examined in localized scleroderma and it was validated in populations lacking localized scleroderma’s distinctive clinical features, possibly underestimating the quality of life impact. This study assessed psychometric properties of the Children’s Dermatology Life Quality Index in a cohort of pediatric localized scleroderma patients.
Methods:
Existing Children’s Dermatology Life Quality Index data from a large pediatric localized scleroderma cohort were analyzed. Children’s Dermatology Life Quality Index score distributions were examined and internal consistency was evaluated with Cronbach’s alpha for the entire Children’s Dermatology Life Quality Index and after deletion of individual items. Construct validity was assessed by calculating Spearman’s correlations between Children’s Dermatology Life Quality Index scores and disease severity/impact measures. Dimensionality was examined using exploratory factor analysis with sequential item elimination.
Results:
Children’s Dermatology Life Quality Index scores suggested modest adverse effects on quality of life. Internal consistency was adequate (Cronbach’s alpha = 0.727) but increased after eliminating items regarding friendships, sleep, and treatment burdens. Children’s Dermatology Life Quality Index scores were not associated with physician-scored disease severity measures but were moderately associated with patient/parent assessments of disease impact. Exploratory factor analysis yielded a three-factor solution encompassing functional limitations, psychosocial effects, and skin symptoms/treatment burden.
Conclusion:
The Children’s Dermatology Life Quality Index may capture functional and psychosocial domains of quality of life in localized scleroderma, but likely underestimates the quality of life impact given that it includes some items with limited relevance in localized scleroderma, incompletely explores skin symptoms and treatment burdens, and demonstrates limited construct validity. Further study to optimize quality of life measurement in pediatric localized scleroderma is warranted.
Keywords: Localized scleroderma, quality of life, pediatrics, psychometrics, skin diseases
Introduction
Pediatric localized scleroderma (LS), also known as morphea, is an autoimmune disease of the skin and underlying tissues. It is characterized by progressive fibrosis, skin thickening, dyspigmentation, and dermal and subcutaneous atrophy that can lead to deformity and disability of the limbs, trunk, and face. 1 LS is “more than a skin disease,” with extracutaneous manifestations (ECMs)—including joint contracture, limb length discrepancies, peripheral arthritis, uveitis, abnormal neurological imaging findings, and gastroesophageal reflux—occurring in at least 25% of patients.2–5
Many inflammatory skin conditions significantly impair quality of life (QoL) in children and adolescents.6–12 Yet surprisingly, studies examining pediatric LS have concluded that LS only modestly impacts QoL, with some authors suggesting that this is a reassuring finding.13–16 However, these studies may be limited by use of QoL measures that have not been validated specifically for use in LS. The most commonly used QoL measure in studies of pediatric LS patients is the Children’s Dermatology Life Quality Index (CDLQI), a dermatology-specific measure of QoL in pediatric skin diseases. The CDLQI was developed and validated primarily in patients with atopic dermatitis, psoriasis, acne, and nevi.17,18
In previous psychometric studies, the CDLQI demonstrated good internal consistency (i.e. Cronbach’s alpha ranging from 0.82 to 0.92), test–retest reliability, responsiveness to change, and correlation with clinical measures. However, its content validity, dimensionality, and minimal clinically important differences remain largely unexamined. 19 In addition, atopic dermatitis and other diseases in which the CDLQI was validated lack the disfiguring fibrosis, musculoskeletal limitations, other ECMs, and intensive immunosuppressive treatments encountered by LS patients.1,17,18 Given these differences, it is unclear whether LS’s impact on QoL is fully represented by the modest scores on the CDLQI, or if these modest scores may be due in part to characteristics of the instrument itself.
Accurate measurement of QoL is important for determining how health conditions affect patients’ lives and for assessing whether medical and non-pharmacologic interventions improve patients’ functional and psychosocial well-being. Since there are not disease-specific QoL measures for LS, determining whether generic instruments such as the CDLQI can be used to effectively measure QoL impact for LS patients is critical for optimizing ongoing research and clinical care. 20 This study examined psychometric properties of the CDLQI in a cohort of LS patients enrolled in the National Registry for Childhood Onset Scleroderma (NRCOS). We aimed to determine whether the CDLQI adequately measures QoL in this population and whether the CDLQI may require further refinement for use in the context of LS.
Methods
Study population
Patients enrolled in NRCOS with a diagnosis of LS and at least one completed CDLQI were eligible for inclusion. Once eligible participants were identified, data were extracted from the NRCOS database. As part of their participation in the NRCOS, parental consent and child assent were obtained for all participants prior to any data collection or research activities. Initial approval was granted by the University of Pittsburgh Institutional Review Board (IRB) in 2003. The sample was limited to 4- to 16-year-olds, as the CDLQI has been validated for this age range.17,18
Study variables
QoL was measured using the 10-item CDLQI (Table 1). Each item was ranked by the patient on a scale from 0 (“not at all”) to 3 (“very much”). Individual item scores were summed to give a total (range: 0–30), with higher scores representing worse QoL. Patients/parents scored a global assessment of disease impact (patient and parent impression of disease impact (Pt-GA and Par-GA), respectively) along a 10-cm visual analog scale (VAS). This specifically asked, “On the horizontal line below, please draw a vertical line to grade how [you have; your child] felt overall about the disease in the past month.”
Table 1.
Ten items of the Children’s Dermatology Life Quality Index (CDLQI).
Item number | Study abbreviation | Original item wording |
---|---|---|
1 | ITCHY/PAINFUL | How itchy, “scratchy,” sore, or painful has your skin been? |
2 | EMBARRASS | How upset or embarrassed, self-conscious, or sad have you been because of your skin? |
3 | FRIENDSHIP | How much has your skin affected your friendships? |
4 | CLOTHES | How much have you changed or worn different or special clothes/shoes because of your skin? |
5 | PLAYING | How much has your skin trouble affected going out, playing, or doing hobbies? |
6 | SPORTS | How much have you avoided swimming or other sports because of your skin trouble? |
7 | SCHOOL/HOLIDAY | Either: If school time: How much did your skin affect your school work? OR: If holiday time: How has your skin problem interfered with your holiday plans? |
8 | TEASING/BULLYING | How much trouble have you had because of your skin with other people calling you names, teasing, bullying, asking questions, or avoiding you? |
9 | SLEEP | How much has your sleep been affected by your skin problem? |
10 | TREATMENT | How much of a problem has the treatment for your skin been? |
Demographic variables, including gender, race/ethnicity, age at initial diagnosis, age at initial enrollment visit, LS disease subtype, and ECMs were accessed via the NRCOS registry database. These variables were documented at initial and follow-up visits using standardized clinical research forms developed based on extensive literature review of other LS cohorts.2–5
Physician-scored LS activity and damage were also extracted from the NRCOS registry database. Physician-scored disease activity measures included the modified Localized Scleroderma Skin Index (mLoSSI) and physician’s global assessment of disease activity (PGA-A). Physician-scored disease damage measures included the Localized Scleroderma Damage Index (LoSDI) and physician’s global assessment of disease damage (PGA-D). The mLoSSI and LoSDI comprise the two sections of the Localized Scleroderma Cutaneous Assessment Tool (LoSCAT), a validated cutaneous disease severity instrument for LS.21–24 The PGA-A and PGA-D were both scored along a 10-cm VAS.
Statistical analysis
In order to examine data encompassing a wide range of disease activity states and treatment durations, only one randomly selected CDLQI score from each eligible participant was used to examine the CDLQI score distributions, internal consistency, and exploratory factor analysis. Descriptive statistics were reported on the demographic and clinical data. The CDLQI total and individual item score distributions were examined for all included patients and separately for specific age groups (i.e. 4–7, 8–12, and 13–16 years). Research in the development of other validated pediatric QoL instruments indicates that QoL measurement tailored to these age ranges is developmentally appropriate. 25
Internal consistency of the CDLQI was assessed using Cronbach’s alpha. 26 To examine whether elimination of any items improved internal consistency, we recalculated Cronbach’s alpha for each possible combination of CDLQI total scores, systematically removing each of the 10 items. Improvements in internal consistency after a particular item was deleted indicated that the scale might be more cohesive without that item.
Exploratory factor analysis was conducted to characterize the underlying structure and dimensionality of the CDLQI. 26 Orthogonal rotation (varimax) was used, as there were low correlations among the factors. Scree plots and eigenvalues (>1.0) were used to determine the number of extracted factors. Factor loadings of 0.3 or greater were considered salient. To determine the most parsimonious number of items with an easily interpretable structure, items were eliminated systematically if they did not load saliently on any factors or loaded saliently on multiple factors. Given that prior analysis suggests all items in the CDLQI should load in the same direction, items loading in opposite directions were considered for elimination if the opposing signs could not be explained well by a logical relationship with the other items in the respective factors.19,27
To assess construct validity, we examined the association of CDLQI scores with physician-scored disease activity (mLoSSI and PGA-A) and damage (LoSDI and PGA-D) and patient/parent global assessments of disease impact (Pt-GA and Par-GA). 26 We expected that disease severity and impact vary in tandem with QoL. Spearman’s correlations (p < 0.05) were calculated between the CDLQI and each of the other outcome measures. When examining construct validity, CDLQI scores from initial study visits and from randomly selected follow-up visits were analyzed separately due to concerns that aggregating these data could potentially mask temporal differences in relationships between CDLQI scores and other outcomes. This concern was borne out by visual inspection of the data, with follow-up visit scores for multiple variables clustered around the low end of the scale, indicating fewer adverse effects of LS on QoL compared with initial visit data. Only participants with complete data (i.e. mLoSSI, LoSDI, PGA-A, PGA-D, Pt-GA, and Par-GA) were included in the construct validity analysis. If these participants also had one or more follow-up visits, one of the eligible visits was randomly selected for analysis.
Results
Study sample and participant characteristics
A total of 94 participants were included in the study (Table 2). The majority of participants were female (73%) and White (92.6%). Median age of symptom onset and at initial NRCOS visit was 8.9 and 12.1 years, respectively. At the study visits used in analysis, 14 participants were between 4 and 7 years old, 41 participants between 8 and 12 years old, and 39 participants between 13 and 16 years old. LS disease subtypes were well represented (Table 2). Out of 94 participants, 39 (41.5%) had at least one ECM present. For those participants who had ECMs, the median number present was 2 (interquartile range (IQR): 1–3). Musculoskeletal ECMs (e.g. joint contractures, limb length/circumference discrepancies, arthralgia/arthritis, muscle weakness, and myalgias) were most prevalent, followed by orofacial ECMs. Neurologic, ocular, and gastrointestinal ECMs were also noted (Table 2). At the study visits analyzed, 79 participants were receiving at least one systemic immunosuppressive medication (e.g. prednisone, methotrexate, or mycophenolate).
Table 2.
Demographics and clinical characteristics (n = 94).
Female sex, n (%) | 69 (73.4%) |
White race, a n (%) | 84 (92.6%) |
Hispanic ethnicity, b n (%) | 5 (5.3%) |
Age at onset (years), median (IQR) | 8.9 (6.8–11.6) |
Age at diagnosis (years), median (IQR) | 9.8 (7.4–12.2) |
Age at initial study visit (years), median (IQR) | 12.1 (9.6–15.1) |
Disease subtype, n (%) | |
Linear, trunk/extremities | 28 (30%) |
Linear, face/scalp | 14 (15%) |
Circumscribed morphea—superficial | 11 (12%) |
Circumscribed morphea—deep | 5 (5%) |
Generalized morphea | 4 (4%) |
Pansclerotic | 1 (1%) |
Mixed subtype | 31 (33%) |
Presence of ECM by category, n (%) | |
All categories | 39 (41.5%) |
Musculoskeletal | 21 (22.3%) |
Orofacial | 16 (17.0%) |
Neurologic | 9 (9.6%) |
Ocular | 4 (4.3%) |
Vascular (i.e. Raynaud’s) | 3 (3.2%) |
GI | 1 (1.1%) |
Other c | 2 (2.1%) |
IQR: interquartile range; ECM: extracutaneous manifestation; GI: glycemic index.
Race not reported for four participants.
Ethnicity not reported for six participants.
Other ECMs include fatigue, subcutaneous nodules, and lipodystrophy.
CDLQI total and individual item score distributions
The CDLQI total scores were generally low (Table 3), indicating only mild adverse effects on QoL and similar score distributions were noted for each age group. When examined in aggregate and by specific age group, all but one of the items showed a majority of participants scoring zero (Figure 1). The exception occurred among 13- to 16-year-olds, with 53.8% scoring 1 or higher on the second item (i.e. EMBARRASS). Across all age groups, EMBARRASS, ITCHY/PAINFUL, and TREATMENT were the three items with the highest proportion of scores greater than zero. The items FRIENDSHIP and SLEEP had the lowest proportion of scores greater than zero across all age groups. We did not find any differences in the median total CDLQI score between participants who were on versus off systemic immunosuppressive medications (median = 2 for both groups, p = 0.981 by Independent Samples Mann–Whitney U test). However, none of the participants off systemic medications rated TREATMENT a 2 or 3, whereas eight of the participants on systemic immunosuppressive medications rated TREATMENT at least as a 2 (n = 5) or 3 (n = 3).
Table 3.
Children’s Dermatology Life Quality Index (CDLQI) total score distributions.
Age group (years) | CDLQI total scores | ||
---|---|---|---|
Median | IQR | Range | |
All ages | 2 | 0–6 | 0–14 |
4–7 | 1 | 0–7 | 0–11 |
8–12 | 2 | 0–4.5 | 0–10 |
13–16 | 3 | 0–6 | 0–14 |
IQR: interquartile range.
Figure 1.
Percentage of participants scoring >0 on individual CDLQI items, by age group.
Internal consistency
Cronbach’s alpha for all items was 0.727. Internal consistency scores calculated by sequentially removing each item and recalculating alpha ranged from 0.658 to 0.742. The overall alpha increased moderately when items 3, 9, and 10 (i.e. FRIENDSHIP, SLEEP, and TREATMENT) were deleted (alpha = 0.729, 0.733, and 0.742, respectively).
Exploratory factor analysis
Both the scree plot and eigenvalues suggested a 3-factor solution (not shown). Four items were candidates for deletion: SLEEP, FRIENDSHIP, SCHOOL/HOLIDAY, and CLOTHES. SLEEP was chosen for elimination because it loaded in opposite directions across factors 1 and 3; based on previous psychometric studies, all CDLQI items should typically be expected to load in the same direction.19,27 SLEEP also loaded negatively on a factor containing multiple items addressing psychosocial items (i.e. EMBARRASS, TEASING/BULLYING, and CLOTHES) which all loaded positively. We could find no reasonable explanation for patients with worse psychosocial impacts to have better sleep quality or vice versa. FRIENDSHIP and SCHOOL/HOLIDAY loaded weakly (<0.3) on all 3 factors and CLOTHES saliently loaded on more than one factor.
The final 6-item 3-factor solution explained a total of 79% of the variance in the CDLQI scores (Table 4). Factor 1 comprised SPORTS and PLAYING, which both relate to physical activity and functional status. Factor 2 contained EMBARRASS and TEASING/BULLYING, with both items relating to psychosocial QoL impact. Factor 3 comprised TREATMENT and ITCHY/PAINFUL; these items relate to treatment burden and skin symptoms, but their relationship to one another is less clear.
Table 4.
Exploratory factor analysis a (n = 94).
Factor 1 | Factor 2 | Factor 3 | |
---|---|---|---|
SPORTS | 0.848 | – | – |
PLAYING | 0.773 | – | 0.349 |
EMBARRASS | – | 0.917 | 0.363 |
TEASING/BULLYING | – | 0.682 | – |
TREATMENT | – | – | 0.533 |
ITCHY/PAINFUL | – | – | 0.519 |
Final three-factor solution after sequential item elimination shown; orthogonal (Varimax) rotation. Factor loadings < 0.3 not shown.
Construct validity
Of the total of 94 participants sampled, 48 had complete data for all variables of interest at initial visit and 43 of those participants also had complete data for at least one follow-up visit. Demographic and clinical characteristics of the selected participants were similar to those of the total NRCOS population (results not shown). The CDLQI moderately correlated with the patient and parent global assessments of disease impact, with follow-up visits showing a stronger relationship than initial visits (Table 5). However, at both initial and follow-up visits, the correlations between CDLQI scores and the physician-scored measures of disease activity and damage were weak and did not reach statistical significance (Table 5).
Table 5.
Relationships between the Children’s Dermatology Life Quality Index (CDLQI) and other outcome measures.
Initial visits (n = 48) |
Follow-up visits (n = 43) |
|||
---|---|---|---|---|
Spearman’s rho | p | Spearman’s rho | p | |
Physician-scored | ||||
mLoSSI | 0.153 | 0.299 | 0.278 | 0.071 |
PGA-A | 0.172 | 0.244 | 0.28 | 0.069 |
LoSDI | 0.23 | 0.116 | 0.273 | 0.077 |
PGA-D | 0.28 | 0.054 | 0.3 | 0.051 |
Patient/parent-scored | ||||
Pt-GA | 0.352 | 0.014 | 0.597 | <0.001 |
Par-GA | 0.403 | 0.004 | 0.532 | <0.001 |
mLoSSI: Modified Localized Scleroderma Skin Index; PGA-A: Physician’s Global Assessment of Disease Activity; LoSDI: Localized Scleroderma Damage Index; PGA-D: Physician’s Global Assessment of Disease Damage; Pt-GA: Patient Global Assessment of Disease Impact; Par-GA: Parent Global Assessment of Disease Impact.
Discussion
To our knowledge, this is the first study assessing the CDLQI’s psychometric properties in the context of LS. As in previous studies, we found consistently low CDLQI scores corresponding to only mild QoL impact.13–16 Our analyses suggest that the CDLQI may be capturing some salient domains of QoL in LS (e.g. functional limitations, psychosocial effects). The CDLQI also demonstrated acceptable internal consistency in LS (α > 0.7), though it was lower than in other conditions (i.e. 0.82–0.92). 19 While these findings suggest that the CDLQI may partially characterize QoL in LS, we would suggest that the low CDLQI scores reflect some underestimation of adverse QoL impact given that: (1) a few items were not relevant in LS, (2) some domains such as skin symptoms and treatment burdens may be only partially captured, and (3) the CDLQI scores were not associated with clinical activity and damage measures.
Our results suggest some CDLQI items have limited relevance for pediatric LS patients. First, some items (i.e. FRIENDSHIP and SLEEP) showed almost no variance in this population, with scores clustered around zero (Figure 1). Removing these items increased internal consistency. Second, exploratory factor analysis with sequential item elimination revealed that some items do not load strongly on any factor (i.e. FRIENDSHIP and SCHOOL/HOLIDAY) or should be eliminated due to cross-loading. The presence of these items may depress the total CDLQI score for LS patients, giving a potentially inaccurate impression that LS only mildly impacts QoL.
The CDLQI may also not fully represent the range of important domains that contribute to QoL in LS, potentially leading to underestimation of the total impact on QoL. While exploratory factor analysis showed functional limitations and psychosocial effects are important domains of QoL captured by the CDLQI (Table 5), the third factor combined the items ITCHY/PAINFUL and TREATMENT and the interpretation of this factor was less clear.
Traditionally, LS has been considered a painless, non-pruritic skin condition, but recent work reveals that sensations of itch, pain, and tightness adversely impact a subset of patients. 16 LS patients are also often treated with systemic immunosuppressive medications (e.g. high-dose prednisone and subcutaneous methotrexate), which can cause many side effects.20,28–30 Our findings concur by showing relatively high rates of QoL impact for the items assessing skin symptoms and treatment burden (Figure 1). The CDLQI collapses all skin symptoms (e.g. itch, pain, and tightness) into a single item and all treatment burdens into another single item, potentially underestimating the impact of each. The ITCHY/PAINFUL and TREATMENT items are difficult to group together conceptually, loading onto a single factor primarily due to the lack of other items in the CDLQI assessing these topics. The increase in Cronbach’s alpha after elimination of TREATMENT further supports that treatment burdens represent a unique domain of QoL in LS. While we did not find differences in the median CDLQI total score for participants on versus off systemic immunosuppressive treatment, we did find that nearly 10% of participants on systemic immunosuppression scored >1 for TREATMENT, suggesting that some significant treatment burdens exist but remain underexplored. An improved approach to QoL measurement in LS should incorporate more detailed information on skin symptoms and treatment burdens and treat these as distinct domains.
Although the CDLQI moderately correlated with the Pt-GA and Par-GA, the lack of association between physician-scored cutaneous activity/damage measures and CDLQI scores raises concern that construct validity of the CDLQI is limited (Table 4). Another study found that while CDLQI and LoSCAT scores were associated in adults with LS, such associations did not hold for children. The authors concluded that children may experience LS uniquely and could require new or modified instruments in order to effectively measure QoL impact. 16
The wide variety of ECMs, such as joint contracture and uveitis, encountered in LS patients sets them apart from populations in which the CDLQI was validated and the CDLQI may only be indirectly assessing the impact of ECMs on QoL.2–5 The developmental context at different ages has also been shown to affect how disfiguring skin conditions affect QoL in growing children. 31 Given the concerns about construct validity raised by our analysis, further study of these areas and their incorporation into QoL measurement in LS may be useful.
There are a few limitations that should be noted. First, this study is exploratory, retrospectively analyzing available registry data in order to assess the CDLQI’s psychometric performance in pediatric LS. Accordingly, the findings should be considered preliminary. Future prospective studies assessing the reliability and validity of this instrument are necessary. Second, given that the study involved secondary data analysis, there are multiple important psychometric properties that we could not study, such as test–retest reliability, interrater (e.g. patient-proxy) reliability, and more detailed examinations of construct and criterion validity. Finally, the study findings are limited by the relatively small sample size, though our study sample is comparable to those described in previous studies for this rare disease.13–16
Despite these limitations, this study’s findings have important implications for patient-reported outcomes research in LS. First, CDLQI scores reflect the importance of functional limitations and psychosocial ramifications for LS patients and significant attention should be paid to these domains. Second, treatment burden and skin-related symptoms, such as itch and pain, may be incompletely assessed by the CDLQI. Future research, including qualitative studies, should explore skin symptoms and treatment burdens in pediatric LS patients. Finally, the CDLQI addresses some but not all relevant domains of QoL in LS. Given the lack of validated patient-reported outcomes for use in this population, we recommend modification of existing instruments or development of a new disease-specific QoL measure as important steps in rigorously assessing outcomes for this population. We hope that this continued refinement of QoL measurement in LS will allow for QoL to be assessed rigorously as a study outcome in future research. Valid tools can be used by researchers to identify high-risk patients and to help clinicians adjust treatment and psychosocial supports for children with LS.
Acknowledgments
The authors thank Thomas Medsger, MD, and Thaschawee Arkachaisri, MD, for establishing the pediatric scleroderma clinic and registry at the University of Pittsburgh. They also thank Cody Caplinger, Christina Mihok, and Mary Lucas for assistance with organizing and maintaining the NRCOS database.
Footnotes
Declaration of conflicting interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding: Dr Torok was supported by a National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) K23 AR059722 Grant, and through the Nancy Taylor Foundation for Chronic Diseases Inc. Dr Ardalan received support from the NIAMS T32 AR052282 Grant.
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