Rasch analysis suggested three unidimensional domains for Affiliate Stigma Scale: additional psychometric evaluation.
OBJECTIVE
To examine the psychometrics of the Affiliate Stigma Scale using rigorous psychometric analysis: classical test theory (CTT) (traditional) and Rasch analysis (modern). Differential item functioning (DIF) items were also tested using Rasch analysis.


METHODS
Caregivers of relatives with mental illness (n = 453; mean age: 53.29 ± 13.50 years) were recruited from southern Taiwan. Each participant filled out four questionnaires: Affiliate Stigma Scale, Rosenberg Self-Esteem Scale, Beck Anxiety Inventory, and one background information sheet.


RESULTS
CTT analyses showed that the Affiliate Stigma Scale had satisfactory internal consistency (α = 0.85-0.94) and concurrent validity (Rosenberg Self-Esteem Scale: r = -0.52 to -0.46; Beck Anxiety Inventory: r = 0.27-0.34). Rasch analyses supported the unidimensionality of three domains in the Affiliate Stigma Scale and indicated four DIF items (affect domain: 1; cognitive domain: 3) across gender.


CONCLUSIONS
Our findings, based on rigorous statistical analysis, verified the psychometrics of the Affiliate Stigma Scale and reported its DIF items. We conclude that the three domains of the Affiliate Stigma Scale can be separately used and are suitable for measuring the affiliate stigma of caregivers of relatives with mental illness.
Department of Psychiatry, Chi Mei Medical Center, 901 Zhonghua Rd., Yongkang Dist., Tainan City 710, Taiwan; Health Service and Population Research Department, Institute of Psychiatry, King's College London, De Crespigny Park, Denmark Hill, London SE5 8AF, United Kingdom; Department of Senior Citizen Service Management, College of Recreation and Health Management, Chia Nan University of Pharmacy and Science, No. 60, Sec. 1, Erren Rd., Rende Dist., Tainan City 71710, Taiwan.
Chih-Cheng
CC
Chang
Department of Psychiatry, Chang Gung Memorial Hospital, No. 6, West Section, Chia-Pu Rd, Pu-Zih City, Chiayi County 61344, Taiwan; Graduate Institute of Clinical Medical Sciences, Chang Gung University, No. 259, Wen-hua 1st Rd., Gui-shan District, Taoyuan City 33302, Taiwan; Department of Nursing, Chang Gung University of Science and Technology, No. 2, West Section, Chia-Pu Rd, Pu-Zih City, Chiayi County 61344, Taiwan.
Jian-An
JA
Su
Department of Psychiatry, Chang Gung Memorial Hospital, No. 6, West Section, Chia-Pu Rd, Pu-Zih City, Chiayi County 61344, Taiwan; Graduate Institute of Clinical Medical Sciences, Chang Gung University, No. 259, Wen-hua 1st Rd., Gui-shan District, Taoyuan City 33302, Taiwan; Department of Nursing, Chang Gung University of Science and Technology, No. 2, West Section, Chia-Pu Rd, Pu-Zih City, Chiayi County 61344, Taiwan.
Ching-Shu
CS
Tsai
Department of Psychiatry, School of Medicine and Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung City, Kaohsiung 807, Taiwan; Department of Psychiatry, Kaohsiung Medical University Hospital, Kaohsiung, 100 Tzyou 1st Road, Kaohsiung City 807, Taiwan.
Cheng-Fang
CF
Yen
Department of Psychiatry, Chi Mei Medical Center, Liouying, 201 Taikang Vil, Liuying Dist., Tainan City 736, Taiwan.
Jiun-Horng
JH
Liu
Department of Public Health, College of Medicine, National Cheng Kung University, 1 University Road, Tainan 701, Taiwan. Electronic address: cylin36933@gmail.com.
Chung-Ying
CY
Lin
D017668:Age of Onset; D001007:Anxiety / Q000453:epidemiology; D017028:Caregivers / Q000523:psychology* / Q000706:statistics & numerical data*; D015897:Comorbidity; D005260:Female; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology* / Q000523:psychology*; D008875:Middle Aged; D011594:Psychometrics / Q000295:instrumentation* / Q000379:methods*; D012649:Self Concept; D057545:Social Stigma; D011795:Surveys and Questionnaires; D013624:Taiwan / Q000453:epidemiology
Affiliate stigma; Caregiver; Classical test theory; Family; Rasch analysis; Severe mental illness