On the development and psychometric testing of the WHO screening instrument to assess disablement in the general population

Abstract The development and psychometric testing of the new World Health Organization (WHO) disablement screening instrument for the general population is described. Two samples were used for the empirical tests: the cross‐cultural sample of the WHO Disablement Assessment Schedule (WHO‐DAS II) field tests in 19 countries (N = 1323), and an Ontario (Canada) general population sample (N = 802). Psychometric tests included procedures from classical test theory as well as analyses based on item response theory (IRT), both parametric and non‐parametric. Results showed that the disablement screener had good properties with respect to classical test theory, but lacked compatibility with respect to IRT criteria. This lack of compatibility with IRT criteria generally leads to a test that must be redefined for each new sample and each time it is administered. Hence, the results reported in this paper suggest that the WHO disablement screener needs revision, if it is to serve as an international cross‐cultural instrument. Copyright © 1999 Whurr Publishers Ltd.