Psychometrican analysis and dimensional structure of the Brazilian version of melasma quality of life scale (MELASQoL-BP)

Maranzatto, Camila Fernandes Pollo; Miot, Hélio Amante; Miot, Luciane Donida Bartoli; Meneguin, Silmara

doi:10.1590/abd1806-4841.20165014

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Investigation • An. Bras. Dermatol. 91 (4) • Jul-Aug 2016 • https://doi.org/10.1590/abd1806-4841.20165014 copy

Psychometrican analysis and dimensional structure of the Brazilian version of melasma quality of life scale (MELASQoL-BP)^* * Study performed at Dermatology Department and Nursing Department of the Medical School of Botucatu - Universidade Estadual Paulista "Júlio de Mesquita Filho" (Unesp) - Botucatu (SP), Brazil.

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract:

Background:

Although asymptomatic, melasma inflicts significant impact on quality of life. MELASQoL is the main instrument used to assess quality of life associated with melasma, it has been validated in several languages, but its latent dimensional structure and psychometric properties haven´t been fully explored.

Objectives:

To evaluate psychometric characteristics, information and dimensional structure of the Brazilian version of MELASQoL.

Methods:

Survey with patients with facial melasma through socio-demographic questionnaire, DLQI-BRA, MASI and MELASQoL-BP, exploratory and confirmatory factor analysis, internal consistency of MELASQoL and latent dimensions (Cronbach's alpha). The informativeness of the model and items were investigated by the Rasch model (ordinal data).

Results:

We evaluated 154 patients, 134 (87%) were female, mean age (± SD) of 39 (± 8) years, the onset of melasma at 27 (± 8) years, median (p25-p75) of MASI scores , DLQI and MELASQoL 8 (5-15) 2 (1-6) and 30 (17-44). The correlation (rho) of MELASQoL with DLQI and MASI were: 0.70 and 0.36. Exploratory factor analysis identified two latent dimensions: Q1-Q3 and Q4-Q10, which had significantly more adjusted factor structure than the one-dimensional model: Χ2 / gl = 2.03, CFI = 0.95, AGFI = 0.94, RMSEA = 0.08. Cronbach's coefficient for the one-dimensional model and the factors were: 0.95, 0.92 and 0.93. Rasch analysis demonstrated that the use of seven alternatives per item resulted in no increase in the model informativeness.

Conclusions:

MELASQoL-BP showed good psychometric performance and a latent structure of two dimensions. We also identified an oversizing of item alternatives to characterize the aggregate information to each dimension.

Keywords:
Factor analysis, Statistical; Melanosis; Quality of life

Variable	Values
N	154
Age (years)^* * Mean (standard deviation);	39 (8)
Gender	N (%)
Female	134 (87)
Male	20 (13)
Marital status	N (%)
Single	42 (27)
Married	93 (61)
Widow	19 (12)
Education	N (%)
Elementary	28 (18)
High school	50 (33)
Higher education	76 (49)
Family income	N(%)
<R$ 1,000	20 (13)
R$ 1,000-3,000	51 (33)
R$ 3,000-5,000	36 (23)
>R$ 5,000	47 (31)
Age of onset of melasma (years)^* * Mean (standard deviation);	27 (8)
Disease duration (years)^ Median (p25-p75)	10 (6-16)
MASI^ Median (p25-p75)	8 (5-15)
DLQI-BRA^ Median (p25-p75)	2 (1-6)
MELASQoL-PB^ Median (p25-p75)	30 (17-44)

	Q1	Q2	Q3	Q4	Q5	Q6	Q7	Q8	Q9	Q10
Q1	-	0.75	0.71	0.59	0.48	0.52	0.38	0.62	0.44	0.53
Q2		-	0.70	0.57	0.52	0.52	0.41	0.61	0.48	0.55
Q3			-	0.66	0.52	0.59	0.39	0.68	0.51	0.56
Q4				-	0.61	0.62	0.48	0.61	0.53	0.62
Q5					-	0.75	0.55	0.63	0.53	0.60
Q6						-	0.56	0.63	0.60	0.57
Q7							-	0.46	0.58	0.49
Q8								-	0.58	0.66
Q9									-	0.69
MELASQoL	0.83	0.85	0.87	0.84	0.81	0.82	0.66	0.88	0.75	0.83

Factor		Initial eigenvalues		Total	Extraction sums of squared loadings
	Eigenvalues	% of variance	% cumulative	Total	% of variance	% cumulative
1	6.75	67.50	67.50	6.48	64.78	64.78
2	1.00	10.00	77.51	0.74	7.39	72.17
3	0.48	4.79	82.30
4	0.45	4.47	86.77
5	0.34	3.39	90.16
6	0.27	2.67	92.83
7	0.25	2.53	95.36
8	0.18	1.83	97.19
9	0.15	1.54	98.73
10	0.13	1.27	100.00

	Factor
	1	2
Q1	-0.14	0.98
Q2	0.00	0.91
Q3	0.14	0.79
Q4	0.58	0.31
Q5	0.86	-0.01
Q6	0.81	0.06
Q7	0.81	-0.11
Q8	0.50	0.42
Q9	0.85	-0.03
Q10	0.74	0.13

	One-dimensional model	Two-dimensional model		Three-dimensional model
Items	Q1-Q10	Q1-Q3	Q4-Q10	Q1-Q4	Q5-Q7+Q10	Q8-Q9
Cronbach’s alpha	0.95	0.92	0.93	0.91	0.89	0.80
Χ²/gl^* * Chi-square ratio for degrees of freedom;	15.43		2.03 (p<0.01)		3.68 (p<0.01)
AGFI^ Adjusted goodness fit index	0.51		0.94		0.88
CFI^* ***** Comparative fit index;	-		0.95		0.87
RMSEA^# # Root mean square error of approximation;	0.31		0.08		0.13
CAIC^## ## consistent Akaike information criterion.	754.80		211.91		259.06

Items	Discrimination	Item	Information score alternative
Items	Discrimination	Item	1	2	3	4	5	6	7
Q1	5.6	170.3	21.1	4.2	0.6	0.5	7.7	5.0	24.9
Q2	5.1	150.4	24.2	3.0	1.5	1.6	5.5	3.5	24.5
Q3	4.2	108.2	26.9	2.8	1.0	1.7	5.9	3.4	22.2
Q4	3.7	78.2	30.4	1.8	1.3	2.6	3.5	2.2	22.2
Q5	4.3	101.7	31.0	1.4	1.0	2.4	4.6	2.6	20.9
Q6	4.8	117.2	31.3	1.7	0.4	2.0	3.4	4.4	20.8
Q7	3.0	63.9	33.6	0.4	0.0	3.6	3.6	8.2	13.7
Q8	4.0	92.2	27.7	1.4	0.7	2.6	3.9	3.8	23.8
Q9	4.2	80.7	33.7	0.5	0.5	3.0	2.1	2.4	21.7
Q10	4.1	85.6	31.5	0.9	0.8	2.2	3.6	2.7	22.4

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