Psychometrics

The QOLIBRI development was undertaken to create a sensitive instrument that can pick up important differences in TBI specific HRQoL. Sensitivity has been shown in two international samples.

Each of QOLIBRI scales is internally consistent (Cronbach’s alpha ranges from 0.75 to 0.89), and shows good test-retest reliability (intraclass correlations ranged from 0.78 to 0.85).

The analysis also indicates that there is a common overall health-related quality of life factor, and this is captured by a total QOLIBRI score. The QOLIBRI Total has good internal consistency (alpha=.95) and good test-retest reliability (ICC=.91). Although the QOLIBRI Total score is useful as an overall summary, the analysis indicates that it does not completely describe variation in HRQoL, and that this is more fully and consistently measured by the profile of individual scales. In factor analysis a single-factor solution accounted for only 37% of the variance, while six factors accounted for 59%.

Structural Equation Modelling indicates a satisfactory fit with a model consisting of six latent variables on one level (i.e. corresponding to the scales), and a “second-order” latent variable (a general QoL factor).

Further details concerning psychometrics in the international sample can be found in von Steinbuechel et al (2010a, 2010b).