CFA
of the R-SFST for patients with schizophrenia living in the community
2.
Method
2.1
Participants
Individuals with schizophrenia were recruited from three community psychiatric
rehabilitation centers and Psychiatric Day Care Center at Taipei City Hospital
in Taiwan in November 2014 to July 2015. Inclusion criteria were as follows:
(1) diagnosis of schizophrenia according to the Diagnostic and Statistical Manual
of Mental Disorders, 5th edition (DSM-V); (2) ages more than 18 years old; (3)
at least graduating from primary school; and (4) ability to understand and
provide informed consent. Exclusion criteria were as follows: (1) severe brain
injuries and impaired cognitive ability and (2) with diagnoses of substance
use. This study was approved by the Institutional Review Board of Taipei City
Hospital.
2.2
Procedures
Participants who met
the inclusion criteria and signed the informed consent were assessed by the
raters. The self-report R-SFST was administered in a quiet environment to groups
of 6-8 participants at a time. Demographic and clinical information of the
participants were collected from clinical records.
2.3
Instrument
Social Function
Scale-Taiwan short version (SFST) is commonly used to measure social function
in patients with schizophrenia (Song, 2001). SFST consists of 36 items divided
in to seven domains: social engagement/withdraw, sociality, interpersonal, independence-competence,
independence-performance, recreation, and employment subscales. However, the
disadvantages of SFST were as follows: (1) high missing rates on items in SFST,
(2) two subscales (independence-competence and independence-performance
subscales) having ceiling effects could not discriminate patients with high
social function, (3) two subscales had low internal consistency (Chiu et al.,
2012). The above results would threaten the validity and reliability of SFST and limit
its utility in both clinical and research settings.
As a result, our study revised SFST into the Revised Social Functioning Scale –Taiwan short version (R-SFST). It
consists of 27 items divided into six domains: 4-item interpersonal
interaction, 5-item sociality, 5-item communications, 4-item leisure
activities, 4-item ability of independence, and 5-item performance of
independence.
2.4
Data analysis
The statistical procedures were computed using SPSS and EQS. The factorial
structure of the general linear model (GLM) was assessed through Confirmatory
Factor Analysis (CFA). CFA was conducted to evaluate the 10 one-factor
structure. The diagonally weighted least squares method was used to estimate
CFA parameters (Forero, Maydeu-Olivares, & Gallardo-Pujol, 2009; Minrdila, 2010).
We examined goodness-of-fit indices to determine the unidimensional construct
of items. Four goodness-of-fit indices were used to examine the level of fit
between the overall model and data, such as the ratio of chi-square value to
the degrees of freedom, comparative fit index (CFI), Tucker-Lewis index (TLI),
and the root mean square error of approximation (RMSEA). The criteria of a good
model fit were χ2 / df<3.0, CFI>0.95, TLI>0.95, and RMSEA<0.08 (Bolle,
1989; Hu and Bentler, 1999; Bentler and Bonnett, 1980; Browne & Cudeck,
1993).
After a domain presented a sufficient model fit, we estimated the factor
loadings of the items to represent the correlation between the item and its
corresponding factor. If the factor loading was <0.50, we deleted the item.
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