Alexandrescu, R., Siegert, R. J., & Turner-Stokes, L. (2015). The Northwick Park Therapy Dependency Assessment scale: a psychometric analysis from a large multicentre neurorehabilitation dataset. Disability and Rehabilation, 37(21), 1976-1983
Contact corresponding author: Richard Siegert
Purpose: To assess the internal reliability, construct and concurrent validity and responsiveness of the Northwick Park Therapy Dependency Assessment (NPTDA) scale.
Method: A cohort of 2505 neurorehabilitation patients submitted to the UK Rehabilitation Outcomes Collaborative
database. Cronbach’s coefficient-a was used to assess internal reliability and factor analysis (FA) to assess construct validity. We compared NPTDA scores at admission and discharge to determine responsiveness.
Results: Coefficient-a for the whole scale was 0.74. The exploratory FA resulted in a four-factor model (Physical, Psychosocial, Discharge planning and Activities) that
accounted for 43% of variance. This model was further supported by the confirmatory FA. The
final model had a good fit: root-mean-square error of approximation of 0.069, comparative fit
index/Tucker–Lewis index of 0.739/0.701 and the goodness of fit index of 0.909. The NPTDA
scores at admission and discharge were significantly different for each of the factors. Expected
correlations were seen between the admission scores for the NPTDA, the Rehabilitation
Complexity Scale (r¼0.30, p50.01) and the Functional Independence Measure (r¼0.25,
p50.01). Conclusions: The scale demonstrated acceptable internal reliability and good
construct and concurrent validity. NPTDA may be used to describe and quantify changes in
therapy inputs in the course of a rehabilitation programme.