What is the diagnostic approach for dyslexia?

Diagnosing Dyslexia: A Comprehensive Approach

The diagnosis of dyslexia requires a comprehensive neuropsychological assessment that includes standardized tests of reading, spelling, and phonological awareness, along with evaluation of cognitive abilities and exclusion of other potential causes of reading difficulties. 1

Core Diagnostic Components

Initial Screening and Assessment

• Standardized developmental screening should begin early, with tools such as:
  • Ages and Stages Questionnaire (ASQ)
  • Parent's Evaluation of Developmental Status (PEDS) 2
• For school-aged children, screening should focus on:
  • Word reading accuracy and fluency
  • Spelling and written expression
  • Phonological processing abilities 1

Comprehensive Diagnostic Evaluation

A complete diagnostic workup for dyslexia should include:

1. Standardized Reading and Spelling Tests

   • Word reading accuracy and fluency assessment
   • Spelling evaluation
   • Reading comprehension measurement 1, 3

2. Phonological Processing Assessment

   • Phonological awareness (ability to identify and manipulate speech sounds)
   • Rapid naming abilities
   • Phonological memory
   • The Comprehensive Test of Phonological Processing (CTOPP-2) is commonly used 3

3. Cognitive Assessment

   • Intelligence testing to establish that reading difficulties aren't due to general intellectual disability
   • Assessment of attention, executive function, and memory 1
   • Commonly used tests include Woodcock-Johnson IV Tests of Achievement 3

4. Criterion-Referenced Assessments

   • Gallistel-Ellis Test of Coding Skills
   • Dynamic Indicators of Basic Early Literacy Skills (DIBELS) 3

Diagnostic Considerations and Pitfalls

Key Diagnostic Criteria

• Significant difficulty with word reading accuracy and fluency
• Problems with spelling and written expression
• Phonological processing deficits
• Difficulties that persist despite adequate instruction and normal intelligence 1

Common Diagnostic Pitfalls to Avoid

• Overreliance on outdated IQ-achievement discrepancy models
• Failure to assess phonological processing
• Attributing reading difficulties solely to behavioral or motivational factors
• Delaying assessment and intervention
• Using unvalidated diagnostic methods 1

Important Contextual Factors

• Test results must be interpreted in context of:
  • Educational background
  • Cultural and linguistic factors
  • Potential confounding variables like fatigue and medication effects 1
• Recognize that 40-60% of dyslexic children have psychological manifestations, including anxiety, depression, and attention deficit 4

Diagnostic Process

1. Gather Background Information

   • Structured interviews with parents and teachers
   • Educational history
   • Family history (dyslexia has a genetic basis) 5, 6

2. Administer Core Diagnostic Tests

   • Word reading test
   • Word spelling test
   • Phonological awareness assessment 7

3. Rule Out Other Conditions

   • Vision and hearing assessment
   • Evaluation for other neurodevelopmental disorders
   • Assessment of psychological state 4

4. Establish Diagnosis Using Multiaxial Classification

   • Document specific reading and spelling deficits
   • Note any comorbid psychological conditions 4

Early Identification

Early identification is critical for better outcomes. For children at risk (e.g., family history of dyslexia), screening should begin in kindergarten with preventive strategies implemented before formal reading instruction begins 1, 4.

The diagnosis of dyslexia should be made by qualified professionals (psychologists, neuropsychologists, or specialized educators) who can administer and interpret standardized assessments and develop appropriate intervention plans based on the specific pattern of strengths and weaknesses identified.