In addition to basic reliability and validity, it is important for health-related assessment tools to be useful in health services research. Specifically, measures must be sensitive to clinically meaningful changes (either improvements or decrements in health status or functioning) and must be able to predict important health-related outcomes of interest.

To examine the WHODAS II's sensitivity to change and predictive validity, health services research studies are being conducted in centres throughout the world during the year 2000.

Sensitivity to Change Field Trials

Goals of the WHO DAS II sensitivity to change field trials are:

1. To establish the WHO DAS II as an instrument which can detect change in disability after treatment or rehabilitation interventions.

2. To compare the effect size of the WHO DAS II to other disability measures.

Predictive Validity Field Trials

Goals of the WHO DAS II predictive validity field trials are: