The polish validation of a disease-specific patient-reported outcome measure of systemic lupus erythematosus

Abstract

Background

LupusPRO is a disease-targeted, patient-reported outcome measure developed for assessing the quality of life in patients with systemic lupus erythematosus. Initially, the questionnaire was validated among U.S. patients of varied ethnic backgrounds and genders. This study aims to carry out a cross-cultural adaptation and validation of the Polish-translated version of LupusPRO.

Method

We administered the Polish version of LupusPRO along with the 36-Item Short Form Health Survey (SF-36) and EQ-5D-5L questionnaire, and the Polish modification of the Hospital Anxiety and Depression Scale (HADS-M). At the same time, we collected demographics and clinical characteristics. Disease activity, damage, and exacerbation were assessed using SELENA-SLEDAI, SLICC/ACR DI and LFA. Furthermore, we tested internal consistency reliability (measured with Cronbach’s alpha), test-retest reliability (using r-Pearson correlation coefficient), convergent validity (against corresponding domains of SF-36) and criterion validity (against disease activity, damage and EQ-VAS), and known group validity.

Results

A total of 199 (91% females) patients with SLE with a mean age of 42.6 ± 12.62 years participated in the study. We observed that the mean SELENA-SLEDAI reached 5.3 (±5.9) points, while SLICC/ACR DI was at 1.3 (±2.0) points. The internal consistency reliability of LupusPRO domains ranged between 0.737 and 0.925 (except for Lupus Symptoms, Social Support, Coping, and Satisfaction with care). For all domains except Social Support, test-retest reliability exceeded 0.7. Convergent validity with corresponding domains of the SF-36 was good (r > 0.5). All health-related quality of life domains performed well against disease activity and damage measures, establishing its criterion validity. Confirmatory factor analysis showed a satisfactory fit. (± expression of range).

Conclusion

The Polish version of LupusPRO has proved to have fair psychometric properties among Polish patients with SLE.

Keywords

Systemic lupus erythematosus quality of life lupusPRO

Introduction

Systemic lupus erythematosus is a chronic inflammatory connective tissue disease of autoimmune origin. The disease significantly affects various spheres of human life: physical, mental, and social. As a result, the quality of life in patients with SLE is substantially decreased compared to the general population, as numerous scientific publications proved.^1–3 Initially, the quality of life in SLE patients was assessed using general questionnaires: SF-36,⁴ WHO-BREF,⁵ and EQ-5D-5L.⁶ However, they all proved imperfect, as these questionnaires did not include many important aspects for lupus patients. Furthermore, the general questionnaires were not sensitive enough to register changes in disease activity.^7,8 In response to their imperfections, researchers have begun to develop new, specific quality-of life questionnaires designed exclusively for patients with lupus: SSC,⁹ SLEQOL,¹⁰ LQOL,¹¹ LupusQOL¹² and LupusPRO.¹³ They all have obtained satisfactory psychometric properties assessment and can be used among SLE patients. The LupusQoL and SLEQOL are disease-specific questionnaires developed to assess health-related quality of life (HRQoL) in patients with systemic lupus erythematosus (SLE), with the LupusQoL being the most frequently used instrument in this context. Of the SLE-specific questionnaires, LupusPRO stands out in particular because of its comprehensive evaluation of the quality of life - taking into account its two dimensions: healthrelated (HRQOL) and non-health-related (non-HRQOOL). It has the advantage of being validated among a U.S. population of SLE patients of both genders with diverse ethnic backgrounds. The original and other validations^14–24 versions have obtained satisfactory assessments of psychometric properties: reliability and validity. So far, no questionnaire specific to SLE has been available in Poland. In this study, we report the results of cross-cultural validation of the Polish version of LupusPRO in patients with SLE.

Methods

LupusPRO has two constructs: health-related (HRQOL) and non-health-related (non-HRQOL) quality of life. The HRQOL domains are Lupus symptoms, Cognition, Lupus medications, Procreation, Physical health, Pain/Vitality, Emotional Problems, and Body image. The non-HRQOL domains are Desires/Goals, Coping, Social support, Satisfaction with medical care, and General health. Individual domains score, total HRQOL, and total non-HRQOL scores range from 0 to 100, where a higher score signifies a better QOL. This study was conducted in four reference Rheumatology Departments in Poland. It was approved by the Institutional Ethics Committee of the Rheumatology Institute in Warsaw. The translation of the US LupusPRO was undertaken using standard guidelines^25,26 to develop the Polish LupusPRO. During the linguistic and socio-cultural adaptation of the LupusPRO questionnaire, no significant difficulties were noted in translating it into Polish and adapting it to Polish conditions. Before inclusion into the study, we obtained informed consent from all patients. The study involved adult patients above 18 years of age with SLE diagnosed based on the SLICC criteria²⁷ from 2012. Data on the following variables were collected during a baseline visit: demographic information, clinical examination, disease activity, and damage assessment. Patients filled out the quality of life questionnaires: the Polish version of LupusPRO, SF-36, and EQ-5D-5L. Higher scores on SF-36 indicate better health. Disease activity was assessed by SELENA-SLEDAI²⁸ scale, and damage was assessed by SLICC/ACR DI.²⁹ In addition, depression and anxiety were evaluated using a Polish modification of the Hospital Anxiety and Depression scale (HADS-M).³⁰ HADS-M assesses the level of the severity of depression and anxiety. Furthermore, patients were handed another LupusPRO to be completed within 2–3 days and returned to the study site or sent by mail. Psychometric properties studied reliability and validity. Under reliability, internal consistency (ICR) was examined, and a test-retest was conducted. The ICR was evaluated using Cronbach’s alpha, where an alpha> 0.7 is considered acceptable.³¹ TRT was tested by assessing agreement between the patient responses to each domain at two-time points. It was evaluated using r-Pearson correlation coefficient. The evaluation of the validity of the Polish version of the LupusPRO questionnaire consisted of examining construct and criterion validity. Convergent validity, the method of validating known groups, and confirmatory factor analysis were analyzed as part of the construct validity assessment. Convergent validity was examined using Spearman’s correlation coefficient by evaluating the correlation strength with related domains on the SF-36v2 and HADS-M. The criterion validity of the polish version of LupusPRO questionnaire was determined by correlation with SELENA-SLEDAI, SLICC/ACR DI and EQ-VAS. Correlations were classified as strong (r > 0.5), moderate (0.3 > r < 0.5), weak (0.1 > r < 0.3), or absent (<0.1). Floor and ceiling effects were analyzed. Known group validity was judged against disease activity (SELENA-SLEDAI) and patient-reported health status (item 1 from SF-36). The conceptual framework (hypothesized item-to-scale relationships) of the LupusPRO was evaluated using confirmatory factor analysis (CFA) appropriate for categorical data. The goodness of fit of the hypothesized item-to-scale relationships (multi-factor) was evaluated with the Comparative Fit Index (CFI), Tucker-Lewis Index (TLI), and Root Mean Square Error of Approximation (RMSEA). It is recommended that CFI and TLI should be 0.9 or greater as evidence of acceptable model fit,³² and RMSEA should be ≤0.08.³³ All reported p values are two-tailed.

Results

One hundred ninety-nine Polish patients (91% females) with SLE with a mean age of 42.6 ± 12.62 years participated in the study. The majority of patients had high and secondary education. About 62.3% of patients were in a stable relationship (marriage or partnership). More than half of the patients (57.2%) were still professionally active. Most patients were taking both corticosteroids and antimalarial drugs. Of the immunomodulatory drugs, methotrexate, mycophenolate mofetil, and azathioprine were used with similar frequency. The mean ± SD SELENA-SLEDAI and SLICC/ACR DI were 5.3 ± 5.9 and 1.3 ± 2.0 (Table 1). Mean scores on the Polish version of LupusPRO domains are shown in Table 2. The lowest scores were recorded in the Emotional problems domain, followed by Desires/Goals and Pain/Vitality, and the highest score was reached in the Satisfaction with medical care domain. The ceiling and floor effects were not observed. Only in the domain of Cognition was the result borderline.

Table 1.

Description of the study cohort (n = 199).

Age in years, mean ⊥ SD	42.6 ± 12.7
Female, %	91
Education, %
Primary	9.5
High school	45.7
College	44.7
Marital status, %
Never married	24.6
Currently married/in stable relationship	62.8
Divorced	9
Widowed	4
Living place, %
Countryside	24.8
Small city 50,000–150,000 inhabitants	34
City >150,000 inhabitants	41.1
Employment status
Unemployed	7
Part-time work	10
Full-time work	47.2
Studied	6
Disability pension	7.5
Retirement pension	22.6
Ethnicity, %	5.2
Caucasian	99.5
Other	0.5
SELENA-SLEDAI, mean ⊥ SD	5.3 ± 5.9
SDI, mean ⊥ SD	1.3 ± 2.0
LFA flare present (%)	24.6%
PCS score, mean ⊥ SD	51.2 ± 13.9
MCS score, mean ⊥ SD	66.9 ± 21.1
EQ-5D-5 L VAS, mean ⊥ SD	68.49 ± 19.6
HADS-M anxiety, mean ⊥ SD	12.27 ± 2.1
HADS-M depression, mean ⊥ SD	9.29 ± 1.7

MCS: mental component summary score; PCS: physical component summary score, SDI: SLICC/American college of rheumatology (ACR) damage index; SLEDAI: safety of estrogens in lupus erythematosus national assessment – SLE disease activity index; VAS: visual analog scale; HADS-M: modified hospital anxiety and depression scale, LFA: lupus foundation of America.

Table 2.

Descriptive scores of the LupusPRO domains in polish patients with SLE.

LupusPRO domain	Mean	SD	Ceiling effect (% max score of 100)	Floor effects (% min score of 100)	Missing responses (%)
Lupus symptoms	61.98	24.63	1.01	8.54	0.00
Cognition	62.37	28.12	6.53	20.60	0.00
Lupus medications	75.60	25.31	2.14	0.00	6.03
Procreation	74.33	32.03	6.98	0.00	35.18
Physical health	74.75	28.30	0.51	0.00	1.51
Pain/vitality	61.94	26.66	2.01	8.04	0.00
Emotional health	55.67	24.72	1.51	4.02	0.00
Body image	67.31	26.80	0.00	18.59	0.00
General health	66.51	19.96	0.00	0.00	1.01
Desires/goals	60.58	25.90	0.50	12.56	0.00
Social support	74.31	26.57	1.66	0.00	9.05
Coping	64.32	24.60	3.52	11.56	0.00
Satisfaction with medical care	81.08	23.51	1.60	0.00	5.53

SLE: systemic lupus erythematosus.

The psychometric properties of Polish version of LupusPRO are summarized in Table 3. The vast majority of the domains (9 out of 12) presented adequate internal consistency and reliability of the tested tool. Unsatisfactory ICR results concerned the domains: Lupus symptoms, Social support, and Coping skills. The results of the Polish version of LupusPRO test-retest were satisfactory. The results oscillated between 0.718 and 0.984. However, TRT was available only in 33 patients. Most did not return the other LupusPRO questionnaire in 2–3 days. The results of convergent validity of the corresponding domains of Polish version of LupusPRO and SF-36v2 showed a strong correlation, except for the Social domain support, where we noted a correlation at the average level. A weak correlation was noted between the juxtaposed Polish version of LupusPRO domains and the scores of the HADS-M Depression and Anxiety subscale. The internal structure of the questionnaire was examined using confirmatory factor analysis. It demonstrated an average fit of the hypothesized model to the data based on the CFI, TLI, and RMSEA scores (Table 4). In the method of known group validity of the domains of LupusPRO against disease activity, higher mean scores were reported in most domains at low disease activity. In contrast, known group validity of the domains of LupusPRO against health status (Question no. 1 of SF-36v2) scores was not able to distinguish between various self-reported overall health statuses (Tables 5 and 6). In the present study, inverse weak but statistically significant correlations were noted between most of the Polish version of LupusPRO domains and the SELENA-SLEDAI and SLICC/ACR DI indices. Only the Lupus Symptoms and Physical health domains showed an inverse average correlation.

Table 3.

Psychometric properties of LupusPRO.

LupusPRO domain	ICR	TRT (n = 33)	Convergent validity (r; p value)	Criterion validity (r; p value)
Lupus symptoms	0.594	0.85	PCS SF-36 (0.51; p < 0.05)	SLEDAI (−0.31; p < 0.05)
				SDI (−0.2; p < 0.05)
				EQ-5D-5 L VAS (0.48; p < 0.05)
Cognition	0.901	0.932		SLEDAI (−0.13; p > 0.05)
				SDI (−0.14; p > 0.05)
				EQ-5D-5 L VAS (0.46; p < 0.05)
Lupus medications	0.737	0.8		SLEDAI (−0.18; p < 0.05)
				SDI (−0.15; p < 0.05)
				EQ-5D-5 L VAS (0.48; p < 0.05)
Procreation	0.883	0.984		SLEDAI (−0.06; p > 0.05)
				SDI (−0.15; p > 0.05)
				EQ-5D-5 L VAS (0.02; p > 0.05)
Physical health	0.894	0.862	Physical function SF-36 (0.58; p < 0.05)	SLEDAI (−0.31; p < 0.05)
			Role physical SF-36 (0.56; p < 0.05)	SDI (−0.22; p < 0.05)
			PCS SF-36 (0.63; p < 0.05)	EQ-5D-5 L VAS (0.48; p < 0.05)
Pain/vitality	0.925	0.894	Bodily pain SF-36 (0.81; p < 0.05)	SLEDAI (−0.24; p < 0.05)
			Vitality SF-36 (0.75; p < 0.05)	SDI (−0.29; p < 0.05)
			PCS SF-36 (0.81; p < 0.05)	EQ-5D-5 L VAS (0.63; p < 0.05)
			EQ-5D-5 L pain/discomfort (−0.73; p < 0.05)	EQ-5D-5 L VAS (0.63; p < 0.05)
Emotional health	0.897	0.867	Mental health SF-36 (0.6; p < 0.05)	SLEDAI (−0.13; p > 0.05)
			Role emotional SF-36 (0.56; p < 0.05)	SDI (−0.23; p < 0.05)
			MCS SF-36 (0.67; p < 0.05)	EQ-5D-5 L VAS (0.59; p < 0.05)
			HADS-M anxiety (0.26; p < 0.05)
			HADS-M depression (−0.17; p < 0.05)
Body image	0.909	0.859		SLEDAI (−0.18; p < 0.05)
				SDI (−0.2; p < 0.05)
				EQ-5D-5 L VAS (0.54; p < 0.05)
Desires/goals	0.84	0.751		SLEDAI (−0.02; p > 0.05)
				SDI (−0.23; p < 0.05)
				EQ-5D-5 L VAS (0.4; p < 0.05)
Social support	0.654	0.153	Social function SF-36 (0.33; p < 0.05)	SLEDAI (−0.12; p > 0.05)
				SDI (0.03; p > 0.05)
				EQ-5D-5 L VAS (0.21; p < 0.05)
Coping	0.632	0.718		SLEDAI (−0.07; p > 0.05)
				SDI (−0.02; p > 0.05)
				EQ-5D-5 L VAS (0.07; p > 0.05)
Satisfaction with care	0.891	0.902		SLEDAI (−0.05; p > 0.05)
				SDI (0.02; p > 0.05)
				EQ-5D-5 L VAS (0.19; p < 0.05)

MCS: mental component summary score; PCS: physical component summary score; ICR: internal consistency reliability; SDI: SLICC/American college of rheumatology (ACR) damage index; SLEDAI: safety of estrogens in lupus erythematosus national assessment – SLE disease activity index; TRT: test-retest reliability; VAS: visual analog scale.

p values <0.0001 for test-retest correlation were statistically significant; p values <0.05 for convergent and criterion validity correlation were statistically significant.

Table 4.

Confirmatory factor analysis of LupusPRO.

LupusPRO domain	Item	Loading
Lupus symptoms	1	0.763
	2	0.605
	3	0.887
Cognition	4	1.046
Cognition	5	1.06
Lupus medications	6	1.026
Lupus medications	7	0.961
Procreation	8	1.77
Procreation	9	1.468
Physical health	10	1.225
	11	1.273
	12	1.105
	13	1.101
	14	0.657
Pain vitality	15	0.862
	16	0.923
	17	1.013
	18	1.157
	19	1.155
Emotional health	20	0.909
	21	0.669
	22	0.902
	23	0.82
	24	1.053
	25	1.128
Body image	26	1.163
	27	0.708
	28	0.933
	29	1.169
	30	1.133
Desires goals	32	0.748
	33	1.062
	34	1.101
	35	0.884
Social support	36	0.859
Social support	37	0.975
Coping	38	0.854
	39	0.825
	40	0.637
Satisfaction with care	41	1.078
	42	1.073
	43	1.101
	44	1.028
Tests of model fit	CFI	0.859
	TLI	0.84
	RMSEA	0.074

CFI: comparative fit index, TLI: tucker-lewis index; RMSEA: root mean square error of approximation.

Table 5.

Known group validity of the Polish version of LupusPRO against patient-reported health status (SF-36 item 1).

LupusPRO domain	Execellent	Very good	Good	Fair	Poor	p
Lupus symptoms	100	82.3	65.7	52.6	36.1	0.012
Cognition	100	82.5	66.6	52.2	36.5	0.091
Lupus medications	100	88.1	83.3	66.3	44.8	0.174
Procreation	100	71.6	75	71.9	100	0.599
Physical health	100	97.2	82	62.5	34.6	0.082
Pain/vitality	100	87.8	72.5	43.4	31.6	0.087
Emotional health	83.3	73.5	62.5	43.6	29.5	0.377
Body image	100	88.6	74.9	53.4	37.1	0.041
General health	100	88.3	74.4	52.1	39.6	0.355
Desires/goals	100	87	63.9	50.9	32.8	0.311
Social support	100	81.8	76.9	69.1	62.5	0.308
Coping	100	66.3	68.4	58.0	61.8	0.979
Satisfaction with medical care	100	89.7	81.9	77.2	77.2	0.613

Table 6.

Known group validity of the polish version of LupusPRO against disease activity by high (≥4) and low (<4) SLEDAI level.

LupusPRO domain	SLEDAI < 4	SLEDAI ≥ 4	p
Lupus symptoms	69,779	56,394	<0.005
Cognition	67,018	59,052	0.046
Lupus medications	85,033	69,144	<0.005
Procreation	75,658	73,264	−.878
Physical health	86,975	66.13	<0.005
Pain/vitality	71,747	54,914	<0.005
Emotional health	60,643	52,119	0.015
Body image	73,599	62,802	0.005
General health	72,639	62,053	<0.005
Desires/goals	67,922	55,334	0.001
Social support	73.48	74,883	0.735
Coping	64,859	63,937	0.795
Satisfaction with medical care	84,704	78,627	0.071

SLEDAI: safety of estrogens in lupus erythematosus national assessment – SLE disease activity index.

Discussion

The complexity of the clinical picture of SLE means that the disease affects various aspects of a patient’s life. Even reasonable control of the disease process is not always reflected in a high quality of life for patients. For this reason, it is vital that the medical care of patients with SLE - in addition to monitoring indicators of clinical disease activity - should also include an assessment of the quality of life, which is a subjective perception of one’s situation in the face of life conditions, including the disease. Failure to take this parameter into account may result in an inadequate grasp of the essence of the patient’s problem and, consequently, result in a lower effectiveness of the overall therapeutic process. In Poland, so far, there have been no linguistically and culturally adapted specific questionnaires available, which has made it difficult for physicians caring for SLE patients to obtain information about their quality of life in accordance with international standards. The Polish version of LupusPRO was cross-culturally adapted and validated. The scores of the individual domains of the Polish version of LupusPRO oscillated between 55.67 and 81.08, which allows us to conclude that the quality of life of the particular dimensions is reduced but is above the average index of possible scores in the questionnaire. The lowest scores were recorded in the Emotional Problems domain, followed by Desires/Goals and Pain/Vitality. The Emotional Problems domain was among the lowest-scoring domains in the other six published LupusPRO validations.^{13,15,17,18,20,23} Emotional disturbances are a leading cause of life impairment in SLE patients.³⁴ They occur twice as often as in the general population.³⁵ At the same time, the literature on the subject indicates frequent omission by attending physicians of the diagnosis of psychiatric disorders of patients.^36,37 This problem requires greater attention and implementation of appropriate procedures into everyday clinical practice. The Polish versions of LupusPRO includes proper results of ceiling and floor effects. Only one borderline results concerning ceiling effects was found in the domain of Cognition. In the study, the Polish version of LupusPRO demonstrated good reliability. The ICR was reliable for most domains. Unsatisfactory ICR results were registered in three domains: Lupus symptoms, Social support, and Coping skills. This may be a result of some limitations of using alpha-Cronbach’s alpha - the small number of items in the test may underestimate its value.³⁸ A lower ICR was observed in original LupusPRO and its language versions and it was associated with the exact domains: Lupus Symptoms^{15–17,19–21} Lupus Treatment,^13,16,17 Social Support^17,23,26 and Coping Skills.^16,19 Each of these contains a small number of items - two or three. In contrast, there was no low ICR in the domains consisting of more issues (four, five, and six issues), which supports the idea that ICR is influenced by the limitations of the alpha-Cronbach’s rule. On the other hand, a lower ICR score indicates a weak correlation between issues, which consequently supports the measurement of different constructs. The Social Support domain assesses whether the patient received sufficient help from family and friends. Poles may treat these social groups differently,³⁹ suggesting some dissociation between the expectation of receiving support from family and friends. A similar pattern was observed in the Coping Skills and Lupus Symptoms domains, where issues included in the domains assessed different constructs. The results of the TRT was satisfactory. One of the main limitations of using TRT is the lack of specification proper, optimal time interval.⁴⁰ Several publications have narrowed the reassessment time for a period from 2 days to 4 weeks^41–43 although there are no clear guidelines indicating the optimal time interval. The results of convergent validity of the corresponding domains of the Polish version of LupusPRO and SF-36 showed a strong correlation, as in other studies.^{13,14,18–21,23} The correlation between the corresponding domains of the Polish version of LupusPRO questionnaire and the HADS-M scale was weak. The reason could be that both subscales of the HADS-M only address selected issues of the analyzed domain of the Polish version of LupusPRO questionnaire. Moreover, the HADS-M scale is not a questionnaire for assessing the quality of life but a method for identifying selected psychiatric disorders. The poor correlation may be related to the fact that the two tools measure different constructs. We also noted weak but statistically significant correlations between domains of Polish LupusPRO and measures of disease activity and damage (except for domains Lupus symptoms and Physical Health) which demonstrates criterion validity. A certain limitation of the study is that the impact of fibromalgia was not examined although previous studies reported its influence on HRQoL.⁴⁴ In conclusion, the assessment of psychometric properties of the Polish LupusPRO showed satisfactory reliability and validity among polish patients with SLE. Evaluation of the quality of life in the Polish population of patients with SLE revealed deficits in the mental sphere.

Footnotes

Declaration of conflicting interests

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

Funding

The authors received no financial support for the research, authorship, and/or publication of the article.

ORCID iDs

A Pękala

M Jolly

References

Cheng

Wang

, et al. The impact of SLE on health-related quality of life assessed with SF-36: a systemic review and meta-analysis. Lupus 2019; 28(3): 371–382.

Thumboo

Strand

. Health-related quality of life in patients with systemic lupus erythematosus: an update. Ann Acad Med Singapore 2007; 36(2): 115–122.

Doria

Rinaldi

Ermani

, et al. Health-related quality of life in Italian patients with systemic lupus erythematosus. II. Role of clinical, immunological and psychological determinants. Rheumatology 2004; 43(12): 1580–1586.

Ware

Sherbourne

. The MOS 36-item short-form health survey (SF-36). I. Conceptual framework and item selection. Med Care 1992; 30: 473–483.

The World Health Organization quality of life assessment (WHOQOL) . Position paper from the world health organization. Soc Sci Med 1995; 41(10): 1403–1409.

EuroQol - a new facility for the measurement of health-related quality of life. Health Policy 1990; 16(3): 199-208.

Kuriya

Gladman

Ibañez

, et al. Quality of life over time in patients with systemic lupus erythematosus. Arthritis Rheum 2008; 59(2): 181–185.

Aggarwal

Wilke

Pickard

, et al. Psychometric properties of the EuroQol-5D and short Form-6D in patients with systemic lupus erythematosus. J Rheumatol 2009; 36(6): 1209–1216.

Grootscholten

Ligtenberg

Derksen

RHWM

, et al. Health-related quality of life in patients with systemic lupus erythematosus: development and validation of a lupus specific symptom checklist. Qual Life Res 2003; 12(6): 635–644.

10.

Leong

Kong

Thong

BYH

, et al. Development and preliminary validation of a systemic lupus erythematosus-specific quality-of-life instrument (SLEQOL). Rheumatology 2005; 44(10): 1267–1276.

11.

Doward

McKenna

Whalley

, et al. The development of the L-QoL: a qualityof-life instrument specific to systemic lupus erythematosus. Ann Rheum Dis 2009; 68: 196–200.

12.

McElhone

Castelino

Abbott

, et al. The LupusQoL and associations with demographics and clinical measurements in patients with systemic lupus erythematosus. J Rheumatol 2010; 37(11): 2273–2279.

13.

Jolly

Pickard

Block

, et al. Disease-specific patient reported outcome tools for systemic lupus erythematosus. Semin Arthritis Rheum 2012; 42(1): 56–65.

14.

Bourré-Tessier

Clarke

Mikolaitis-Preuss

, et al. Cross-cultural validation of a disease-specific patient-reported outcome measure for systemic lupus erythematosus in Canada. J Rheumatol 2013; 40(8): 1327–1333.

15.

Navarra

Tanangunan

Mikolaitis-Preuss

, et al. Cross-cultural validation of a disease-specific patient-reported outcome measure for lupus in Philippines. Lupus 2013; 22(3): 262–267.

16.

Inoue

Shiozawa

Yoshihara

, et al. The Japanese LupusPRO: a cross-cultural validation of an outcome measure for lupus. Lupus 2017; 26(8): 849–856.

17.

Pinto

Jolly

Dhooria

, et al. Hindi LupusPRO: cross cultural validation of disease specific patient reported outcome measure of lupus. Lupus 2019; 28(13): 1534–1540.

18.

Jolly

Toloza

Block

, et al. Spanish LupusPRO: cross-cultural validation study for lupus. Lupus 2013; 22(5): 431–436.

19.

Mok

Kosinski

, et al. Validation of the LupusPRO in Chinese patients from Hong Kong with systemic lupus erythematosus. Arthritis Care Res 2015; 67(2): 297–304.

20.

Kaya

Goker

Cura

, et al. Turkish lupusPRO: cross-cultural validation study for lupus. Clin Rheumatol 2014; 33(8): 1079–1084.

21.

Devilliers

Jolly

Samson

, et al. Validation of the French version of lupus patient reported outcome (LupusPRO), a disease-specific patient reported outcome for lupus patients [abstract]. Arthritis Rheumatol 2016; 68(10): 1776–1778.

22.

Jolly

Mazzoni

Cicognani

. Measurement properties of web based lupuspro, a disease targeted otcome tool, among Italian patients with lupus. Value Health 2015; 18(3): A302.

23.

Elkaraly

Nasef

Omar

, et al. The Arabic LupusPRO: a cross-cultural validation of a disease-specific patient-reported outcome tool for quality of life in lupus patients. Lupus 2020; 29(13): 1727–1735.

24.

Han

Cho

Nam

, et al. Korean LupusPRO: cross-Cultural validation study for systemic lupus erythematosus. Lupus 2022; 31(12): 1498–1507.

25.

Wild

Grove

Martin

, et al. Principles of good practice for the translation and cultural adaptation process for patient-reported outcomes (PRO) measures: report of the ISPOR task force for translation and cultural adaptation. Value Health 2005; 8(2): 94–104.

26.

Beaton

Bombardier

Guillemin

, et al. Guidelines for the process of crosscultural adaptation of self-report measures. Spine 2000; 25(24): 3186–3191.

27.

Petri

Orbai

Alarcõn

, et al. Derivation and validation of the systemic lupus international collaborating clinics classification criteria for systemic lupus erythematosus. Arthritis Rheum 2012; 64(8): 2677–2686.

28.

Petri

Kim

Kalunian

, et al. Combined oral contraceptives in women with systemic lupus erythematosus. N Engl J Med 2005; 353(24): 2550–2558.

29.

Gladman

Ginzler

Goldsmith

, et al. The development and initial validation of the systemic lupus international collaborating clinics/American college of rheumatology damage index for systemic lupus erythematosus. Arthritis Rheum 1996; 39(3): 363–369.

30.

Walden-Głuszko

Majkowicz

. Praktyczna ocena efektywności opieki paliatywnej - wybrane techniki badawcze. Ocena Jakości Opieki Paliatywnej w Teorii i Praktyce. Gdańsk: Wyd: Akademia Medyczna w Gdańsku, 2000, pp. 21–39.

31.

Hays

Anderson

Revicki

. Psychometric considerations in evaluating health-related quality of life measures. Qual Life Res 1993; 2(6): 441–449.

32.

Bentler

. Cutoff criteria for fit indexes in covariance structure analysis: conventional criteria versus new alternatives. Struct Equ Model 1999; 6(1): 1–55.

33.

Carle

Riley

Hays

, et al. Confirmatory factor analysis of the patient reported outcomes measurement information system (PROMIS) adult domain framework using item response theory scores. Med Care 2015; 53(10): 894–900.

34.

Jolly

Sequeira

Block

, et al. Sex differences in quality of life in patients with systemic lupus erythematosus. Arthritis Care Res 2019; 71(12): 1647–1652.

35.

Ainiala

Loukkola

Peltola

, et al. The prevalence of neuropsychiatric syndromes in systemic lupus erythematosus. Neurology 2001; 57(3): 496–500.

36.

Fonseca

Bernardes

Terroso

, et al. Silent burdens in disease: fatigue and depression in SLE. Autoimmune Dis 2014; 2014: 790724.

37.

Beckerman

Auerbach

Blanco

. Psychosocial dimensions of SLE: implications for the health care team. J Multidiscip Healthc 2011; 4: 63–72.

38.

McDowell

. The theoretical and technical foundations of health measurement. Measuring Health: A Guide to Rating Scales and Questionnaires. Oxford Scholarschip: Oxford Univercity Press, 2009, pp. 30–53.

39.

Centrum Badania Opinii Społecznej . Komunikat z badań: Nie Ma jak rodzina. (2019). https://cbos.pl/SPISKOM.POL/2019/K_022_19.PDF

40.

Jankowski

Zajenkowski

. Metody szacowania rzetelności pomiaru testem. Psychometria. Podstawowe zagadnienia. Fronczyk K. Wyd: Wyższa Szkoła Finansów i Zarządzania w Warszawie. Warszawa: Vizja Press & IT, 2009, pp. 84–110.

41.

Streiner

Norman

Cairney

. Reliability. Health measurement scales: a practical guide to their development and use. Oxford: Wyd: Oxford University Press, 2008.

42.

Aday

Cornelius

. Designing and conducting health surveys: a comprehensive guide. San Francisco: Wyd: Jossey-Bass, 2006, pp. 48–80.

43.

Burns

Grove

. The practice of nursing research: conduct, critique, and utilization. Philadelphia: Wyd: W. B. Saunders, 2001.

44.

Etchegaray-Morales

Méndez-Martínez

Jiménez-Hernández

, et al. Factors associated with health-related quality of life in Mexican lupus patients using the LupusQol. PLoS One 2017; 12(1): e0170209.