Development of a specific health-related quality of life test in drug abusers using the Rasch rating scale model.

A test has recently been designed for the measurement of health-related quality of life in drug abusers (Health-Related Quality of Life for Drug Abusers Test - HRQOLDA Test) based on the bi-axial concept of addiction. The aim of this work is to find out the metric properties of the test by applying the polytomous Rasch Rating Scale Model (RSM). The HRQOLDA Test was given to a sample of 358 drug abusers who began treatment in a Therapeutic Community. The Rating Scale Model (RSM) and the WINSTEPS programme were used for the analysis of its metric properties. The results shown here are an overall fit of data to the model. The items are adequately distributed over the HRQOL continuum. The response categories appear to be in order except for the category 'a little'. The test region which measures most accurately, and is most informative, is in the middle of the continuum. The test properties studied confirm the adequacy of the RSM for accurate measurement of HRQOL in drug abusers, providing a test for measuring this specific construct in this population.