[Development of patient-reported outcome scale for myasthenia gravis: a psychometric test].
OBJECTIVE
To investigate the scientificity of patient-reported outcome (PRO) scale for myasthenia gravis (MG), which was used to evaluate the clinical effects of traditional Chinese and Western medicine treatment on MG patients. Psychometric performance of the MG-PRO scale was also expected to be evaluated in this study.


METHODS
A total of 100 MG patients and 100 healthy people were face-to-face interviewed by well-trained investigators, and the data of MG-PRO scale were collected. The classical theory test (CTT) and item response theory (IRT) methods were used to analyze the psychometric performance such as validity, reliability, person separation index (PSI) and differential item functioning (DIF) in the MG-PRO scale.


RESULTS
The results of CTT analysis showed that the split-half reliabilities of the MG-PRO scale and each dimension were greater than 0.7. In the analysis of internal consistency of each dimension, the Cronbach's alpha was greater than 0.8. Each facet had greater correlation with its dimension than the other dimensions. Four principal components were extracted by exploratory factor analysis, which represented all dimensions of the scale, and the cumulative variance was 55.54%. The scores of each of the 8 facets between MG patients and healthy people were different (P<0.01). The results of IRT showed that the PSI of each model was greater than 0.8, and all items did not have uniform DIF and non-uniform DIF.


CONCLUSIONS
The MG-PRO scale reflects the definition and connotation of quality of life and contains special issues of MG patients as well, and shows good reliability (split-half reliability, Cronbach's alpha), validity (content validity, construct validity, discriminate validity) from the results of CTT, and good psychometric performance from the results of IRT.
Chen
Xin-lin
XL
Department of Preventive Medicine and Health Statistics, College of Basic Medical Sciences, Guangzhou University of Chinese Medicine, Guangzhou 510407, Guangdong Province, China.
Liu
Feng-bin
FB
Guo
Li
L
Liu
Xiao-bin
XB
D000328:Adult; D001699:Biometry; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008516:Medicine, Chinese Traditional; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000523:psychology* / Q000628:therapy*; D011594:Psychometrics; D015203:Reproducibility of Results; D057566:Self Report; D016896:Treatment Outcome