Differential diagnostic assessment is used to establish the diagnosis of (severe) dyslexia. In the assessment, severity of the reading and spelling problems and the underlying cognitive profile including indications and contraindications for severe dyslexia are examined. In this differential diagnostic assessment, severe non-comorbid dyslexia is distinguished from mild dyslexia, from other reading problems and from multiple problems. The diagnostic method follows the guidelines of the protocol ‘Dyslexia Diagnosis and Treatment 2.0’ (Blomert (2006) and College voor Zorgverzekeringen (Cvz, 2013).
Treatment of dyslexia
Children and adults with severe dyslexia are treated with the LEXY-method at the IWAL institute. The LEXY-method is a psycholinguistic treatment, which is consistent with the international consensus with respect to cause and treatment of dyslexia. LEXY is a computer based treatment program, aimed at recognizing and using phonological and morphological word structure. The core of the treatment is the relationship between spoken and written language. Training is directed at speech sound skills, links between sound and letter (or groups of letters) and a control system of (inferential) algorithms based on phonological and morphological principles. The LEXY treatment is highly structured and is supported by the computer program LEXY. This program consists of six different modules with separate contents, each with increasing complexity. Although each client works through the material in the same order, the pace at which the material is treated depends on the client’s speed in attaining mastery level (the ‘mastery learning’ principle).
In the individual LEXY treatment, clients receive a weekly one-hour treatment session (45 minutes of contact time and 15 minutes preparation/reporting time). Clients practice three times a week for 15 minutes with teaching material provided by the practitioner. In general, treatment duration is 12 to 18 months (40 to 60 sessions). Progress is assessed every 15 sessions and 9 months after treatment termination.
The effectiveness of the LEXY treatment has been extensively evaluated in scientific studies. With respect to external validity, short term and long term clinical effects on reading and spelling were demonstrated in different studies: a) after treatment, clients achieve functional reading and spelling levels; b) these reading and spelling levels are enduring; c) the vast majority of the client population shows clinically meaningful benefits from treatment; d) treatment effects are not negatively affected by individual differences (such as intelligence, socioeconomic status, severity of the reading level at start of treatment and age); e) clients subjectively experience treatment as positive and effective (Tijms, Hoeks, Paulussen-Hoogeboom, Smolenaars, 2003; Tijms, 2005, 2008, Tijms & Hoeks, 2005).
Moreover, with respect to internal validity, research has indicated that cascading improvement during treatment of dyslexic children is closely associated with the presentation order of treatment components. This demonstrates the direct link between specific treatment ‘ingredients’ and treatment working mechanisms (Tijms, 2004, 2007).
These results have been published in various international scientific journals. Furthermore, the Health Care Insurance Board concerned with reimbursement for dyslexia treatment in the Netherlands used these results as evidence for the effectiveness of dyslexia treatment in the official Dutch reimbursement policy (Reij, 2003). Moreover, the effectiveness of the LEXY treatment is emphasized in several recent scientific national (Blomert, 2005) and international (Elliot, Davidson, & Lewin, 2007; Goetry, Nossent, & Van Hecke, 2006) peer reviewed review studies.