[PMH16] Use of Rasch models for validation of instruments used in mental health evaluation

[PMH16] Use of Rasch models for validation of instruments used in mental health evaluation

2001 Value in health

Lancon, C. | Toumi, M. | Pettersson, Ã. | Aballea, S. | Fournier, A. | Volume: 4, Issue: 2, Pages: 145, poster, model, mental health, scale, Depression, Schizophrenia, methods, Quality of Life, Questionnaires,

OBJECTIVES: The Positive And Negative Syndrome
Scale (PANSS) and Calgary Depression Scale for Schizophrenics
(CDSS) are widely used in the evaluation of
schizophrenia. Their internal validity have already been
evaluated with classical methods (multitrait and confirmatory
analyses). During the last two decades, Item Response
Theory has been developed to deal with latent
traits. As part of it, Rasch models are commonly used in
Quality of Life research but not yet for other outcome
questionnaires. METHODS: 458 schizophrenic patients
were evaluated with the PANSS and CDSS. Rasch models
for polytomous items were fitted to the data in order to
assess: 1) unidimensionality of the CDSS and the PANSS
subscales, i.e. their ability to measure one latent trait (degree
of depression/degree of positive, negative, general
schizophrenic symptoms); infit and outfit statistics were
used and residuals studied; 2) invariance of comparisons,
implying that the parameter characterizing an item does
not depend on the latent trait distribution of the population;
item parameters estimates were compared for two
subgroups of the population. RESULTS: Unidimensionality
and invariance of comparisons are globally satisfactory
for the CDSS, although the appropriateness of two
items (items four and seven) may be questionable. Results
do not support the three-dimensional structure for the
PANSS, which is commonly used as the reference. CONCLUSIONS:
Further investigation of the factorial structure
of PANSS (e.g five-factors structures, which have
been proposed by several authors) is necessary. Rasch
models provide a powerful approach to evaluate internal
validity of mental health scales, enabling to investigate
invariance of comparisons, which constitutes the major
distinction from classical methods.

https://www.doi.org/10.1046/j.1524-4733.2001.40202-202.x