Rasch psychometric validation of the Impact on Participation and Autonomy questionnaire in people with Parkinson's disease.
OBJECTIVE
The aim of this study was to assess the psychometric properties of the Impact on Participation and Autonomy (IPA) questionnaire, in its two scales: IPA-I, perceived limitations in participation and autonomy; IPA-II, perceived problems in participation.


METHODS
The IPA data underwent Rasch analysis for rating scale diagnostics and a reliability and validity study. The work and education domain was left out of the analysis due to its low applicability to our subjects. A convenience sample of 100 patients with Parkinson's disease (PD) (41 male, 59 female; mean age 72+/-7 years) were consecutively observed at our Rehabilitation Clinic.


RESULTS
According to Rasch analysis, two response categories of IPA-I were collapsed into one and 1 item (''intimate relationship'') was deleted. The remaining 24 items fitted the unidimensional construct that the scale was intended to measure. IPA-I demonstrated good reliability (person separation = 0.93, item separation = 0.97) and internal construct validity. All six IPA-II items proved to belong to the same construct. For IPA-II, item separation = 0.97, person separation = 0.71. The targeting and spread of item difficulty and the quite low person separation reliability of IPA-II made it possible only to differentiate people with low vs high level of problems in participation. Both scales showed the expected correlation with PD-specific clinical and quality of life measures.


CONCLUSIONS
IPA-I shows promise as a tool for measuring participation in people with PD. IPA-II has acceptable psychometric characteristics for measuring perceived problems in participation. Additional steps to improve their metric properties and further studies in people with different kinds of health conditions need to be carried out.
Franchignoni
F
F
Unit of Occupational Rehabilitation and Ergonomics, Salvatore Maugeri Foundation, Clinica del Lavoro e della Riabilitazione, IRCCS, Veruno, Italy. ffranchignoni@fsm.it
Ferriero
G
G
Giordano
A
A
Guglielmi
V
V
Picco
D
D
D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology*; D026684:Personal Autonomy; D011594:Psychometrics; D011788:Quality of Life; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires