On the structure of motor symptoms of Parkinson's disease.

This study aims to investigate the structure of the motor symptoms of Parkinson's disease (PD), as measured by the Motor Section of the Unified Parkinson's Disease Rating Scale (UPDRS). The dimensionality of the Motor Section of the UPDRS was studied using structural equation modeling. The UPDRS measures were obtained from 405 patients with PD [237 men (39 "off", 170 "on", 28 unknown) and 168 women (21 "off", 140 "on", 7 unknown)].

Mokken scale analysis of the UPDRS: dimensionality of the Motor Section revisited.

The dimensionality and reliability of the Motor Section of the Unified Parkinson Disease Rating Scale (UPDRS III) was studied with non-parametric Mokken scale analysis. UPDRS measures were obtained on 147 patients with PD (96 men, 51 women, mean age 61, range 35-80 yrs). Mokken scale analysis revealed a four-dimensional structure of the UPDRS III.

The Treatment Motivation Scales for forensic outpatient treatment (TMS-F): construction and psychometric evaluation.

The Treatment Motivation Scales for forensic outpatient treatment (TMS-F) is a Dutch 85-item self-report questionnaire for the motivation of forensic outpatients to engage in their treatment and six cognitive and affective determinants of this motivation. Following descriptions of the conceptual basis and construction, the psychometric properties of the TMS-F are evaluated in two studies. In Study 1 (N = 378), the factorial structure of the instrument and the dimensionality of its scales are evaluated by confirmative factor analysis.

Validation of the Treatment Motivation Scales for Forensic outpatient treatment (TMS-F).

The validity of the Treatment Motivation Scales for outpatient offender treatment (TMS-F), a self-report questionnaire with scales for the motivation of patients to engage in the treatment and six cognitive and emotional determinants of this motivation, is evaluated in two studies. In Study 1 (N = 620), the construct validity of the TMS-F is investigated applying a multitrait-multimethod design with a therapist-rating instrument as the criterion method. All scales were found to have adequate convergent validity and acceptable discriminant validity.

The true-change model with individual method effects: reliability issues.

The true intra-individual change model is generalized by defining individual method effects. This allows the analysis of non-congeneric test-retest variables assumed to measure a common, possibly (temporally) transient, attribute. Temporal change in the attribute between different times of measurement is modelled by the true-change variable.

Structural equation analysis of a hypothesised symptom model in the autism spectrum.

Background: Several studies showed a different symptom structure underlying the spectrum of autistic-like disorders from the behaviour triad as mentioned in the DSM-IV. In the present study, a hypothesised symptom model for autism was constructed, based on earlier explorative findings, and was put to a confirmatory test.

Method: Items from the Autism Diagnostic Interview-Revised (ADI-R) were used to examine the goodness of fit of the DSM-IV model, the hypothesised symptom model, and two additional models for autism.