Examining the validity and reliability of the Taita symptom checklist using Rasch analysis.

Background/purpose: The Taita symptom checklist (TSCL) is a standardized self-rating psychiatric symptom scale for outpatients with mental illness in Taiwan. This study aimed to examine the validity and reliability of the TSCL using Rasch analysis.

Methods: The TSCL was given to 583 healthy people and 479 people with mental illness. Rasch analysis was used to examine the appropriateness of the rating scale, the unidimensionality of the scale, the differential item functioning across sex and diagnosis, and the Rasch cut-off score of the scale.

Results: Rasch analysis confirmed that the revised 37 items with a three-point rating scale of the TSCL demonstrated good internal consistency and met criteria for unidimensionality. The person and item reliability indices were high. The TSCL could reliably measure healthy participants and patients with mental illness. Differential item functioning due to sex or psychiatric diagnosis was evident for three items. A Rasch cut-off score for TSCL was produced for detecting participants' psychiatric symptoms based on an eight-level classification.

Conclusion: The TSCL is a reliable and valid assessment to evaluate the participants' perceived disturbance of psychiatric symptoms based on Rasch analysis.