Diagnostics of dyslexia in young adults: a validation study of the Interactive Dyslexia Test Amsterdam - Antwerp (IDAA)

Introduction: Until recently dyslexia in young adults received little attention in scientific research. Most of the traditional Dutch tests fail to focus on the age category of +16 years and are not adequately validated. In collaboration with the University of Amsterdam, we therefore developed a computerised diagnostic instrument that targets the core phenomenon of dyslexia: severe reading and spelling disabilities at the word level. The aim of this study is to investigate the congruent validity of the IDAA and to integrate this instrument in the diagnostics of dyslexia using a holistic approach. Methods: Eighty-one young adults (40M/41F) with and fifty-two young adults (19M/33F) without dyslexia (16-18y) from all educational levels took part in this study. Components of the reading and spelling process were measured with traditional and IDAA subtests. Results: Binary logistic regression analyses revealed that the IDAA subtests adequately predicted the presence of automatised word recognition, phonological decoding, orthographical competence and phonological competence (resp. 86.4, 80.3, 86.4 and 87.9% correct classification). The traditional and IDAA subtests correlate significantly (r=0.16-0.78). Discussion: The current findings give clear indications for a rationalised use of diagnostic instruments: The IDAA subtests adequately predict the 4 components of the reading and spelling process but socio-demographic factors such as age and educational level should still be taken into account. Therefore, we present a holistic approach of dyslexia integrating each of the 4 components of the reading and spelling process as well as an analysis of the strengths and weaknesses of the young adult.