The Japanese LupusPRO: A cross-cultural validation of an outcome measure for lupus

Abstract

Objective

This study aimed to validate the Japanese version of the LupusPRO questionnaire for use with systemic lupus erythematosus patients.

Methods

Participants were 205 lupus patients recruited from three rheumatology centers in Japan. Demographic data were collected and quality of life was assessed using the LupusPRO and the Short Form Health Survey-12. Disease activity was evaluated by physicians using the Systemic Lupus Erythematosus Activity Index. Some participants completed questionnaires 10–14 days after the first survey. Internal consistency reliability, test-retest reliability, content validity and convergent validity were examined, and confirmatory factor analysis was performed.

Results

Participants’ mean age was 47.8 ± 13.6 years. Older participants scored lower on physical quality of life and higher on coping than younger participants. The LupusPRO showed satisfactory test-retest reliability (n = 111). Test-retest reliability was lower for the mental and social aspects of quality of life, indicating fluctuations in quality of life during the two-week interval. Internal consistency reliability was good and convergent validity with the corresponding domains of the Short Form Health Survey-12 was satisfactory. Confirmatory factor analysis showed a good model fit.

Conclusion

The Japanese LupusPRO is a reliable and valid measure to evaluate treatment interventions for systemic lupus erythematosus.

Keywords

Systemic lupus erythematosus quality of life patient-reported outcomes

Introduction

Systemic lupus erythematosus (SLE) is an autoimmune disease that results in multiple organ damage.¹ Advances in medical treatment have substantially improved SLE survival rates, and the number of elderly SLE patients is expected to increase.² SLE patients have lower quality of life (QoL) than rheumatoid arthritis patients.^3–6 Five QoL scales have been developed to investigate SLE patients’ perspectives on the impact of the disease;^7–11 however, none of these scales have been translated into Japanese.

One of these SLE-specific QoL scales is the Lupus Patient Reported Outcome Too (LupusPRO), which was developed in the United States.¹¹ It measures procreation, coping, desires/goals and satisfaction with care, which are not addressed by the other SLE-specific scales. The LupusPRO has been used to evaluate the effect of interventions^12,13 and has been translated into four languages, including Spanish, French, Turkish and Chinese.^14–17 The LupusPRO has been validated in several English-speaking countries.^18,19

The purpose of this study was to establish the reliability and validity of the Japanese version of the LupusPRO. Japanese SLE patients are unique, as they are covered by a special medical assistance program that covers almost all medical expenditure. Easy access to medical care means that Japanese samples are more varied in age and represent a greater range of disease duration than samples in previous validation studies.^11,14–17

Methods

Translation and establishment of the reliability and validity of the Japanese LupusPRO

The LupusPRO comprises two constructs: health-related QoL and non-health-related QoL. The health-related QoL domains are (1) lupus symptoms, (2) cognition, (3) lupus medications, (4) procreation, (5) physical health, (6) pain/vitality, (7) emotional health and (8) body image. The non-health-related QoL domains are (1) desires/goals, (2) social support, (3) coping and (4) satisfaction with care. In total, the LupusPRO comprises 43 items (30 for the health-related QoL construct, 13 for the non-health-related QoL construct) that relate to the past four weeks in the patient’s daily life. Each item is scored on a five-point Likert scale ranging from “none of the time” to “all of the time.” The score for each domain ranges from 0 to 100; higher scores indicate better QoL.

We obtained permission to develop the Japanese version of the LupusPRO from Dr Meenakshi Jolly, the author of the original version. The LupusPRO was translated by the first author following the guidelines for translation of the instrument.²⁰ The Japanese version was back-translated. It was compared with the original scale, and minor modifications were made to the Japanese version. The face validity of the Japanese version was tested by four SLE patients and an expert panel (three rheumatologists and two nurses), and minor changes were made to clarify the wording. Then, the expert panel was asked to evaluate each item using a Likert scale ranging from 1 (not relevant) to 4 (highly relevant). We calculated the content validity index for each item and the mean content validity index for the scale. Content validity indices for the scale and for each item were tabulated. A cutoff of 0.90²¹ was considered the minimum acceptable validity.

Participants

We recruited outpatients at three rheumatology centers (university hospital, city hospital, private hospital) in western Japan between June 2015 and February 2016. Eligibility criteria were (1) age ≥20 years, (2) meeting the American College of Rheumatology classification criteria for SLE,²² (3) ability to complete the self-administered questionnaires in Japanese and (4) written informed consent to participate in the study. An age of ≥20 years was chosen as this is the legal age of adulthood in Japan; therefore, participants did not require parental consent to take part. Consecutive patients who attended the outpatient department were screened for eligibility and were contacted by the first author. The exclusion criteria were (1) a major comorbidity that would affect QoL, such as the terminal stage of cancer and (2) overlap with other autoimmune diseases, such as rheumatoid arthritis.

Ethical considerations

This study was approved by the Ethics Committee of Osaka University and three rheumatology centers (ethics committee approval numbers: 14505 (319)-2). At the initial contact with the participants, the first author provided a verbal and written explanation to confirm their willingness to participate. After obtaining written informed consent, the first author distributed the questionnaires to participants.

Data collection

The self-administered questionnaires were used to collect demographic information, information about SLE duration and QoL data using a generic health-related QoL tool (Medical Outcomes Study Short Form Health Survey-12, SF-12)²³ and the LupusPRO. The following demographic information was obtained: gender, age, educational attainment, employment status and family structure. The SLE Disease Activity Index (SLEDAI)²⁴ was used to determine disease activity, and information on current SLE medications was collected. The SLEDAI information was abstracted from electronic medical records by the primary physician and included laboratory results, health history since last visit and physical examination data. A flare was defined as an increase of ≥3.0 in the total SLEDAI score between the previous visit and the date of the survey.²⁴

To examine test-retest reliability, approximately half the participants, 127 patients, were asked to fill out the questionnaires 14 days after the first survey and return them to the first author in a pre-stamped addressed envelope. An interval of 14 days was chosen following previous recommendations for reliability testing of psychometric scales, which all specify a 14-day interval and advocate a range of two days to four weeks.^25–27

Statistical analyses

Descriptive statistics were calculated for all variables. Then, demographic and QoL data were stratified by two age groups (<50, ≥50 years) by biological reproductive age, a definition used by the World Health Organization.²⁸ This age cutoff point was chosen for age stratification because the procreation subscale score could have affected the LupusPRO health-related QoL score. T-tests were used for parametric variables and Wilcoxon rank-sum tests were used for non-parametric variables to test the statistical significance of differences between the two age groups.

Cronbach’s alpha was used to examine internal consistency for each LupusPRO domain; an alpha of >0.7 was considered acceptable.²⁹ Correlation coefficients between item scores at the two time points were calculated to assess test-retest reliability.

Content validity, convergent validity and construct validity were evaluated. Content validity was evaluated using the content validity index for the scale and the indices for each item; a coefficient >0.9 was considered acceptable.²¹ Convergent validity was evaluated using Spearman’s correlations between the LupusPRO domains and the corresponding SF-12 domains.

To test construct validity, a confirmatory factor analysis of the LupusPRO item responses was performed using a robust weighted least squares estimator. The goodness of fit of the hypothesized item-to-scale relationships was evaluated using the comparative fit index, the Tucker-Lewis index (which is also a comparative fit index) and the root mean square error of approximation. The comparative fix index and the Tucker-Lewis index quantify the difference between the examined and independence model; higher scores indicate larger differences. The root mean square error of approximation quantifies the difference to the fully saturated model. It is generally recommended that acceptable fit requires a comparative fit index and Tucker-Lewis index ≥0.90^30,31 and a root mean square error of approximation ≤0.08.³²

JMP 11 (SAS, Cary, NC, USA) was used for descriptive analysis and SPSS Amos 24 (IBM, Armonk, NY, USA) was used for confirmatory factor analysis. All reported p values are two tailed, and p values <0.05 were considered statistically significant. There are several adjustment methods available for multiple comparisons; however, they tend to increase type II errors.³³ Therefore, we did not adjust for type II errors.

Results

The content validity indices for the scale and each item of the Japanese LupusPRO were evaluated by five experts. The mean content validity index for the scale score was 0.99, and the mean content validity index for each item score was 0.99.

The first author contacted 211 eligible SLE outpatients for study participation. Of those, three declined to participate, and one had an advanced stage of cancer and was excluded. Of the remaining 207, two participants produced questionnaires with several missing values and thus were excluded from the analysis. In total, 205 patients produced complete questionnaires. Participants’ mean age was 47.8 ± 13.6 years, and 91.8% were women (Table 1). The median SLE duration was 15.0 years, and nearly two-thirds of participants had a SLEDAI score of 4.0. Approximately 95% of participants used oral corticosteroids, but none used topical corticosteroids. Forty-two percent of participants took immunosuppressive drugs (Table 1).

Table 1

Descriptive data for the study participants

Variables	All participants		Age<50		Age≥50		p value of reproductive stage
Variables	(n = 205)		(n = 129)		(n = 76)		p value of reproductive stage
Age (mean, ± SD) years	47.8	±13.6	39.1	±6.7	62.6	±8.7
Female (%)	91.8		93.0		89.4
Education (%)
< High school	8.3		4.7		14.5
High school	38.5		31.0		51.3
Junior college	31.2		38.8		18.4
College	18.0		20.9		13.2
More than college	3.9		4.7		2.6
Education (mean, ±SD) year	4.4	±2.2	4.8	±2.0	3.7	±2.3	0.0004
Employment status (%)
Full time	24.0		32.0		10.0
Part time	26.0		29.0		20.0
None	50.0		39.0		70.0
Living alone (%)	8.8		6.2		13.2		0.09
Disease duration (median, IQR) years	15.0	(13.0)	13.0	(11.5)	19.0	(13.0)	< 0.0001
Medications (%)
Corticosteroids	95.1		92.2		96.1
Prednisolone	90.7		85.3		88.1
Methylprednisolone	5.4		6.2		3.9
Betamethasone	0.4		0.8		0.0
Corticosteroid; PSL equivalent, mg/day (median, IQR)	5.0	(5.4)	5.0	(6.4)	5.0	(2.4)	0.11
Tacrolimus	18.5		23.3		10.5
Mycophenolate mofetil	11.2		12.4		9.2
Cyclosporine	5.1		7.0		2.6
Mizoribine	4.9		6.2		2.6
Azathioprine	2.9		3.1		2.6
Methotrexate	2.4		1.6		4.0
Hydroxychloroquine	0.4		0.7		0.0
SLEDAI (median, IQR)	4.0	(3.0)	4.0	(3.5)	2.0	(3.0)	0.41
SLEDAI (%)
≤4	73.1		71.3		56.6
5–12	25.7		27.1		22.4
≥13	1.5		1.6		1.3
Moderate flare^a	5.9		7.0		3.9

IQR: interquartile range; PSL: prednisolone; SLEDAI: Systemic Lupus Erythematosus Disease Activity Index; ^aA flare was defined as an increase of ≥3.0 in the total SLEDAI score between the previous visit and the date of the first survey.

Participants <50 years (hereafter, the younger group) had significantly more years of schooling than participants ≥50 years old (hereafter, the older group). The younger group had significantly shorter disease duration than the older group. There was no difference in disease activity (based on SLEDAI scores) and corticosteroids use between the two age groups. In contrast, the use of immunosuppressive drugs was more common in the younger group (Table 1).

Regarding generic QoL, SF-12 scores were higher for physical function, body pain and social function, and lower for vitality. After stratifying by age, the younger group had significantly higher median scores for the three physical domains, but lower median scores for mental health, than the older group.

Scores for the physical and non-physical aspects of the LupusPRO domains showed a similar pattern to SF-12 scores. The physical health-related LupusPRO domains showed higher scores, whereas the coping and social support domains showed lower scores. However, the median score range varied substantially from 12.5 for social support to 85.0 for body image. After stratifying by age, the younger group had significantly better physical and emotional health, and significantly higher cognition and desires/goals scores, than the older group. However, the older group had significantly higher median coping scores than the younger group (Table 2).

Table 2

Descriptive statistics for LupusPRO and SF-12 scores in Japanese lupus patients (0 = worst QoL, 100 = best QoL)

Domain	All participants		Age<50		Age≥50		p value of reproductive stage
	(n = 205)		(n = 129)		(n = 76)
	Median	(IQR)	Median	(IQR)	Median	(IQR)
SF-12
SF-12 PCS score	41.9	(23.7)	45.1	(17.2)	27.9	(24.3)	<0.0001
SF-12 MCS score	51.6	(10.0)	50.6	(10.9)	52.3	(8.9)	0.007
Physical Function	75.0	(50.0)	100.0	(25.0)	50.0	(43.8)	<0.0001
Role Physical	75.0	(50.0)	75.0	(50.0)	50.0	(46.9)	<0.0001
Bodily Pain	75.0	(50.0)	75.0	(50.0)	75.0	(50.0)	0.09
General Health	60.0	(35.0)	60.0	(35.0)	25.0	(35.0)	<0.0001
Vitality	50.0	(50.0)	50.0	(20.0)	50.0	(50.0)	0.05
Social Function	75.0	(50.0)	75.0	(50.0)	75.0	(50.0)	0.76
Role Emotional	75.0	(50.0)	75.0	(50.0)	62.5	(34.4)	0.006
Mental Health	62.5	(25.0)	62.5	(25.0)	62.5	(25.0)	0.62
LupusPRO
HRQoL	72.5	(28.3)	74.2	(30.0)	68.3	(26.7)	0.04
Lupus symptoms	83.3	(33.3)	88.3	(33.3)	83.3	(33.3)	0.85
Cognition	75.0	(50.0)	87.5	(37.5)	75.0	(50.0)	0.05
Lupus medications	75.0	(56.3)	87.5	(62.5)	75.0	(50.0)	0.90
Procreation	50.0	(100.0)	75.0	(100.0)	0.0	(100.0)	0.002
Physical health	90.0	(30.0)	95.0	(20.0)	90.0	(48.8)	0.01
Pain/Vitality	80.0	(35.0)	85.0	(35.0)	77.5	(43.8)	0.28
Emotional health	62.5	(50.0)	66.7	(43.7)	56.3	(49.0)	0.03
Body image	85.0	(45.0)	80.0	(50.0)	90.0	(45.0)	0.14
Non-HRQoL	48.1	(21.1)	46.2	(22.2)	52.9	(16.8)	0.08
Desires/Goals	75.0	(46.9)	75.0	(43.8)	62.5	(35.9)	0.01
Social Support	12.5	(50.0)	12.5	(50.0)	25.0	(50.0)	0.66
Coping	41.7	(50.0)	33.3	(58.3)	58.3	(33.3)	<0.0001
Satisfaction with care	50.0	(50.0)	50.0	(50.0)	50.0	(50.0)	0.71

HRQoL: health-related quality of life; IQR: interquartile range; MCS: Short Form Health Survey-12 mental component summary score; PCS: Short Form Health Survey-12 physical component summary score.

Of the 12 LupusPRO domains, Cronbach’s alpha did not reach 0.7 for four domains (lupus symptoms, lupus medications, social support and coping).

To assess test-retest reliability of the LupusPRO, 127 participants were asked to complete the questionnaires a second time. Of those, 12 did not return the questionnaires and four had many missing values and were excluded from the analysis. In total, 111 participants completed the second questionnaires. Correlations ranged from 0.54 for coping to 0.82 for body image (Table 3). Domains related to lupus, such as pain and body image, had higher coefficients, and domains related to coping tended to have lower coefficients. The correlations for the SF-12 scores ranged from 0.47 for social function to 0.88 for physical function.

Table 3

Reliability and validity of the Japanese LupusPRO

LupusPRO domain	Reliability				Validity
	Cronbach’s coefficient alpha	Test-retest correlation coefficient			Convergent validity
	Cronbach’s coefficient alpha	Japanese LupusPRO^a	SF-12^a		Correlation coefficient
	(n = 205)		(n = 111)		(n = 205)
Lupus symptoms	0.43	0.66			SLEDAI-alopecia	−0.22	0.001
					SLEDAI-rash	−0.30	0.003
					SLEDAI-arthritis	−0.02	0.741
Cognition	0.80	0.59
Lupus medications	0.64	0.63
Procreation	0.93	0.70
Physical health	0.85	0.76	Physical Function	0.88	Physical Function	0.53	<0.0001
			Role Physical	0.69	Role Physical	0.63	<0.0001
					PCS	0.62	<0.0001
Pain/Vitality	0.90	0.80	Vitality	0.65	Vitality	0.48	<0.0001
			Body Pain	0.66	Body Pain	0.59	<0.0001
Emotional health	0.88	0.75	Mental Health	0.66	Mental Health	0.42	<0.0001
			Role Emotional	0.74	Role Emotional	0.32	<0.0001
					MCS	0.30	<0.0001
Body image	0.93	0.82
Desires/Goals	0.77	0.65	General Health	0.69
Social support	0.64	0.62	Social Function	0.47
Coping	0.59	0.54
Satisfaction with care	0.76	0.66

MCS: Short Form Health Survey-12 mental component summary score; PCS: Short Form Health Survey-12 physical component summary score; SLEDAI: Systemic Lupus Erythematosus Disease Activity Index. ^aAll p values for test–retest correlation coefficients were <0.0001.

Convergent validity was tested using the SLEDAI subscales; SLEDAI-alopecia and SLEDAI-rash had significant but weak inverse correlations. Convergent validity of the three LupusPRO domains was examined by calculating correlations between the LupusPRO domains and the corresponding SF-12 domains. Physical health, pain/vitality and emotional health showed moderate correlations with the corresponding SF-12 domains (Table 3).

Table 4 shows the results of the confirmatory factor analysis. The model fit indices were as follows: the comparative fit index = 0.87, the Tucker-Lewis index = 0.85 and the root mean square error of approximation = 0.06 (Table 4).

Table 4

Confirmatory factor analysis results for the Japanese LupusPRO (n = 205)

	Factor loadings
Factor 1
Lupus symptoms
Loss of hair	0.34
New rash	0.35
Lupus flare	0.63
Factor 2
Cognition
Poor memory	0.76
Lack of concentration	0.87
Factor 3
Lupus medications
Meds cause side effects	0.64
Concerned over number of meds	0.74
Factor 4
Procreation
Ability to have baby	0.92
Ability to prevent pregnancy	0.95
Factor 5
Physical health
Taking care of personal needs	0.55
Getting in and out of bed	0.48
Fulfilling family responsibilities	0.91
Taking care of dependents	0.88
Burden to family	0.82
Factor 6
Pain/Vitality
Woke up feeling worn out	0.64
Felt pain	0.79
Unable to do usual activities	0.82
Performing activities take long	0.90
Limited in kinds of activities	0.91
Factor 7
Emotional health
Worried about lupus impact	0.81
Worried about losing income	0.49
Anxious	0.89
Depressed	0.56
Concerned lupus leads to more…	0.87
Concerned lupus last a long time	0.92
Factor 8
Body image
Dislike my appearance	0.89
Thought less of myself	0.82
Lacked control over appearance	0.88
Self-conscious about appearance	0.90
Embarrassed about how others…	0.86
Factor 9
Desires/Goals
Ability to plan	0.46
Overall life satisfaction	0.97
Enjoyment of life	0.89
Fulfill career goals	0.47
Factor 10
Social support
Receive support from friends	0.63
Receive support from family	0.77
Factor 11
Coping
Focus on making situation better	0.81
Learned to live with lupus	0.84
Comfort/strength from religion	0.13
Factor 12
Satisfaction with care
Dr accessible	0.39
Dr understood	0.77
Dr provided information	0.81
Dr discussed/monitored side effects	0.68
Tests of model fit
CFI	0.870
TLI	0.852
RMSEA	0.066

CFI: comparative fit index; TLI: Tucker–Lewis index; RMSEA: root mean square error of approximation.

Discussion

We established the reliability and validity of the Japanese LupusPRO in a sample of 205 patients and found that age was associated with QoL. Further, the low test–retest reliability indicated fluctuations in non-physical-related QoL during a two-week interval.

As expected, the older group perceived their physical health to be worse compared with the younger group. Similarly, the mental aspects of QoL, as measured by both the generic and disease-specific QoL scales, were worse for the older group than for the younger group. Our findings support those of previous studies. An Italian study by Rinaldi et al. compared QoL in 126 SLE patients and healthy controls (age range: 25–64 years).³⁴ They found that in SLE patients, mean SF-36 physical health and mental health scores linearly decreased with increasing age, whereas scores for the healthy controls did not decrease with increasing age. A study of health-related QoL in patients with rheumatic disorders showed that older patients had worse QoL scores related to physical and social relationships than younger patients.³⁵ Our results showed that the older group had higher LupusPRO coping scores than the younger group, but the former had worse health-related QoL than the latter. Further research is needed to explore the effect of age on QoL to identify areas for intervention.

The test–retest reliability scores showed fluctuations in the LupusPRO emotional health and social support domains. In contrast, the physical aspects of LupusPRO were relatively stable. A similar pattern was found for SF-12 QoL scores. Of those LupusPRO test-retest validation studies using intervals of two to three days, three studies showed relatively high agreement for most of the domains,^14–17 whereas the original LupusPRO validation study found low correlations (<0.7) for satisfaction with care, procreation, desires/goals and social support.¹¹ Differences in data collection methods and demographic characteristics may account for these inconsistent findings. Our participants completed the first questionnaire after finishing their physician consultation and completed the second questionnaire at home. They may have had more time to reflect on social support and emotional health issues. Previous studies lack descriptions of how these data were collected.^14–17 Regarding demographic differences, our sample had a greater range of both age and SLE duration compared with participants in previous LupusPRO validation studies.^11,14–17

Regarding the internal consistency of the LupusPRO, Cronbach’s alpha for lupus symptoms, lupus medications, social support and coping domains was less than optimal.²⁹ Cronbach’s alpha increases with the number of items in a domain,³⁶ and these domains comprise only a few items. Overall, the test-retest reliability of the Japanese LupusPRO was satisfactory and was in agreement with previous studies.^11,14–17

We also established the content validity, convergent validity and construct validity of the Japanese LupusPRO. The content validity index was high and the face validity of the scale was established. Moderate correlations between the Japanese LupusPRO domains and the corresponding SF-12 domains demonstrated convergent validity. The weak correlation between the Japanese LupusPRO scores and the SLEDAI symptom scores (alopecia and rash) indicate that disease activity is not a good predicator of QoL in SLE patients, which is in accordance with previous studies.^37,38 The confirmatory factor analysis results confirmed the construct validity of the LupusPRO.

One study limitation was that data were drawn from only some areas of western Japan. Another limitation is that only the SLEDAI was used to evaluate disease activity or organ damage. However, previous studies also found small correlations between these clinical indicators and the LupusPRO.^11,14–17

A major finding of this study was that participants perceived that they had a low level of social support. Compared with provision for rheumatoid arthritis patient groups, there are few SLE self-help groups in Japan and online resources are limited. The formation of support groups and the improvement of online resources are urgently needed.

Fluctuations in mental and emotional aspects of QoL are of concern for health care professionals as well as for patients. We found that domain scores for social function, cognition and coping fluctuated more than scores for physical domains in the two-week interval. A similar pattern was found for SF-12 scores. Perceived lack of social support may indicate SLE participants’ vulnerability to stress, which would affect QoL related to social function, cognition and coping. Qualitative research is necessary to explore Japanese SLE patients’ perceptions of social support and other related QoL domains.

Conclusion

These findings demonstrate the reliability and validity of the Japanese version of the LupusPRO. We found that older participants had generally lower median QoL domain scores than younger participants. However, older participants seemed to cope better with SLE than younger participants. We also found that the social and mental aspects of QoL, as measured by the Lupus PRO and the SF-12, tended to fluctuate more than the physical aspects during a two-week interval. Health care professionals need to be attentive to the vulnerability of SLE patients. Future research is necessary to examine which factors predict QoL in SLE patients.

Footnotes

Acknowledgments

We would like to thank all patients who participated in this study and the staff at the three clinics that cooperated with the data collection. We would also like to acknowledge Dr. Atsushi Kumanogoh, Dr. Yasushi Tanaka, Dr. Chihiro Tanaka, and Dr. Noriaki Yoh for supporting this project.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The first author (MI) received a research assistant scholarship for this project from Osaka University.

References

Sutanto

Grewal

McNeil

. Experiences and perspectives of adults living with systemic lupus erythematosus: Thematic synthesis of qualitative studies. Arthritis Care Res 2013; 65: 1752–1765.

Shakra

. Do improved survival rates of patients with systemic lupus erythematosus reflect a global trend? J Rheumatol 2008; 35: 1906–1908.

Wolfe

Michaud

Katz

. EQ-5D and SF-36 quality of life measures in systemic lupus erythematosus: Comparisons with rheumatoid arthritis, no inflammatory rheumatic disorders, and fibromyalgia. J Rheumatol 2010; 37: 296–304.

Castelino

Abbott

McElhone

Teh

. Comparison of the psychometric properties of health-related quality of life measures used in adults with systemic lupus erythematosus: A review of the literature. Rheumatology 2012; 52: 684–696.

Chehab

Carnarius

Schneider

. What matters for lupus patients? Presse Med 2014; 3(6 Pt 2): e197–e207.

Holloway

Humphrey

Heron

. Patient-reported outcome measures for systemic lupus erythematosus clinical trials: A review of content validity, face validity and psychometric performance. Health Qual Life Outcomes 2014; 12: 116–116.

Leong

Kong

Thong

. Development and preliminary validation of a systemic lupus erythematosus-specific quality of life instrument (SLEQOL). Rheumatology 2005; 44: 1267–1276.

McElhone

Abbott

Shelmerdine

. Development and validation of a disease-specific health-related quality of life measure, the Lupus Qol, for adults with systemic lupus erythematosus. Arthritis Rheum 2007; 57: 972–979.

Moses

Wiggers

Nicholas

Cockbun

. Development and psychometric analysis of the systemic lupus erythematosus need questionnaire (SLENQ). Qual Life Res 2006; 16: 461–466.

10.

Doward

McKenna

. The development of the L-QoL: A quality-of-life instrument specific to systemic erythematosus. Ann Rheum Dis 2009; 68: 196–200.

11.

Jolly

Pickard

Block

. Disease-specific patient reported outcome tool for systemic lupus erythematosus. Semin Arthritis Rheum 2012; 42: 56–65.

12.

Jolly

Garris

Mikolaitis

. Development and validation of the Lupus Impact Tracker: A patient-completed tool for clinical practice to assess and monitor the impact of systemic lupus erythematosus. Arthritis Care Res 2014; 66: 1542–1550.

13.

Jolly

Kristin

Mikolaitis

Evans-Raoulk

Block

. Body image intervention to improve health outcomes in lupus: A pilot study. J Clin Rheumatol 2014; 20: 403–410.

14.

Jolly

Toloza

Block

. Spanish LupusPRO: Cross-cultural validation study for lupus. Lupus 2013; 22: 431–436.

15.

Mok

Kosinski

Chan

Jolly

. Validation of the LupusPRO in Chinese patients from Hong Kong with systemic lupus erythematosus. Arthritis Care Res 2015; 67: 297–304.

16.

Kaya

Goker

Cura

. Turkish lupusPRO: Cross-cultural validation study for lupus. Clin Rheumatol 2014; 33: 1079–1084.

17.

Bourré-Tessier

Clarke

Kosinski

. The French-Canadian validation of a disease-specific, patient-reported outcome measure for lupus. Lupus 2014; 23: 1452–1459.

18.

Navarra

Tanangunan

Mikolaitis-Preuss

Kosinski

Block

Jolly

. Cross-cultural validation of disease-specific patient-reported outcome measure for lupus in Philippines. Lupus 2013; 22: 262–267.

19.

Bourré-Tessier

Clarke

Mikolaitis-Preuss

. Cross-cultural validation of a disease-specific patient-reported outcome measure for systemic lupus erythematosus in Canada. J Rheumatol 2013; 40: 1327–1333.

20.

Sousa

Rojjanasrirat

. Translation, adaptation and validation of instruments or scales for use in cross-cultural health care research: A clear and user-friendly guideline. J Eval Clin Pract 2011; 17: 268–274.

21.

Polit

Beck

. The content validity index: Are you sure you know what’s being reported? Critique and recommendations. Res Nurs Health 2006; 29: 489–497.

22.

Aletaha

Tuhina

Alan

. Updating the American College of Rheumatology revised criteria for the classification of systemic lupus erythematosus. Ann Rheum Dis 2010; 69: 1580–1588.

23.

Fukuhara

Suzukamo

. Manual of SF-36v2 Japanese version, Kyoto: Institute for Health Outcomes & Process Evaluation Research, 2004.

24.

Karlson

Liang

Eaton

. A randomized clinical trial of a psychoeducational intervention to improve outcomes in systemic lupus erythematosus. Arthritis Rheum 2002; 50: 1832–1841.

25.

Burns

Grove

. The Practice of nursing research conduct, critique, & utilization, 4th ed. Philadelphia: Sanders, 2001, pp. 396–396.

26.

Aday

. Designing & conducting health surveys, 2nd ed. San Francisco: Jossey-Bass, 1996, pp. 53–53.

27.

Streiner

Norman

. Health measurement scales. A practical guide to their development and use, 4th ed. Oxford: Oxford University Press, 2008182.

28.

Booth

. Demographic forecasting: 1980 to 2005 in review. Int J Forecast 2006; 22: 547–581.

29.

Hays

Anderson

Revicki

. Psychometrics considerations in evaluating health-related quality of life measures. Qual Life Res 1993; 2: 441–449.

30.

Bentler

. Cutoff criteria for fit indexes in covariance structure analysis: Conventional criteria versus new alternatives. Struct Equ Modeling 1998; 6: 1–55.

31.

Jackson

Gillaspy

Purc-Stephenson

. Reporting practice in confirmatory factor analysis: An overview and some recommendations. Psychol Methods 2009; 14: 6–23.

32.

Carle

Riley

Hays

. Confirmatory factor analysis of the patient reported outcomes measurement information system (PROMIS) adult domain framework using item response theory scores. Med Care 2015; 53: 894–900.

33.

Barash

. Clinical anesthesia, Philadelphia: Williams & Wilkins, 2013, pp. 199–199.

34.

Rinaldi

Doria

Salaffi

. Health-related quality of life in Italian patients with systemic lupus erythematosus. I. Relationship impact of age. Rheumatology 2004; 43: 1574–1579.

35.

Goulia

Voulgari

Tsifetaki

Drosos

Hyphantis

. Comparison of health-related quality of life and associated psychological factors between younger and older patients with established rheumatic disorders. Aging Ment Health 2010; 14: 819–827.

36.

McDowell

Newell

. Measuring health. A guide to rating scales and questionnaires, 2nd ed. Oxford: Oxford University Press, 1996, pp. 41–41.

37.

Alarcón

McGwin

Jr Brooks

. Systemic lupus erythematosus in three ethnic groups. XI. Source of discrepancy in perception of disease activity: A comparison of physician and patients visual analog scale scores. Arthritis Rheum 2002; 47: 408–413.

38.

Jolly

Utset

. Can disease specific measures for systemic lupus erythematosus predict patients health related quality of life? Lupus 2004; 13: 924–926.