What is the recommended approach to diagnose dyslexia?

Diagnosing Dyslexia: A Comprehensive Assessment Approach

The diagnosis of dyslexia requires a comprehensive neuropsychological assessment that includes standardized tests of reading, spelling, and phonological awareness as core components, with additional evaluation of cognitive abilities and exclusion of other potential causes of reading difficulties.

Core Diagnostic Components

1. Standardized Assessment of Reading and Language Skills

• Reading assessment: Evaluate word decoding, fluent word recognition, rapid automatic naming, and reading comprehension 1
• Spelling assessment: Document difficulties with written language 1
• Phonological awareness testing: Assess the ability to recognize and manipulate basic sounds in language 2

2. Cognitive Assessment

• Intelligence testing: While IQ scores don't determine dyslexia diagnosis, cognitive assessment helps establish that reading difficulties aren't due to general intellectual disability 2, 3
• Processing speed evaluation: Measure cognitive processing speed using tests like Number Connection Test or Trail Making Test 4
• Working memory assessment: Evaluate attention span and working memory capacity 4

3. Additional Evaluations

• Language abilities: Assess expressive and receptive language, verbal fluency, and comprehension 4
• Executive function: Evaluate planning, organization, and mental flexibility 4
• Psychological assessment: Screen for anxiety, depression, and attention deficits, which co-occur in 40-60% of dyslexic children 5

Diagnostic Process

1. Initial screening:

   • Obtain structured interviews with parents and teachers about reading difficulties 6
   • Document family history (dyslexia has a genetic basis) 2
   • Review developmental milestones, especially language development

2. Formal testing:

   • Administer standardized reading and spelling tests 5
   • Compare performance to age-appropriate norms
   • Document significant difficulty with speed and accuracy of word decoding 2

3. Differential diagnosis:

   • Rule out vision problems (though vision problems alone don't cause dyslexia) 7
   • Exclude primary hearing or neurological disorders
   • Consider comorbid conditions like ADHD or anxiety disorders 5

Key Diagnostic Criteria

• Significant difficulty with word reading accuracy and fluency
• Problems with spelling and written expression
• Phonological processing deficits
• Difficulties persist despite adequate instruction and normal intelligence
• Problems cannot be better explained by intellectual disability, uncorrected sensory problems, or lack of educational opportunity

Important Considerations

• Early identification is critical for better outcomes 5
• Test results must be interpreted in context of educational background, cultural factors, and potential confounding variables 4
• Diagnosis should be established using a multiaxial classification system 5
• The diagnosis is not based on a single test but on a pattern of difficulties across multiple assessments
• Avoid relying on vision-based diagnostic procedures that lack scientific support 7

Diagnostic Pitfalls to Avoid

• Overreliance on IQ-achievement discrepancy models, which are outdated
• Failure to assess phonological processing, which is central to dyslexia
• Attributing reading difficulties solely to behavioral or motivational factors
• Delaying assessment and intervention, which reduces effectiveness
• Using unvalidated or scientifically unsupported diagnostic methods 7

By following this structured diagnostic approach, clinicians can accurately identify dyslexia and distinguish it from other learning or developmental disorders, enabling appropriate and timely intervention.