The Pieces of a Dyslexia Diagnostic Assessment

Parents frequently ask me how a diagnosis of dyslexia is made. Recently, one parent questioned whether there was one test for dyslexia because she was told that an IQ test would be the sole test used to determine whether her son was dyslexic. In the past, intelligence tests were a part of the testing battery, but this is no longer the recommended practice. Here is an article from NIH that explains why we no longer use IQ for determining dyslexia. I suggested that the parent who inquired might consider sharing this article with her son’s team.

There is no one test that diagnoses dyslexia. Rather, making a diagnosis of dyslexia requires looking at a number of areas—oral language comprehension and use, including phonological processing, as well as reading, spelling, and writing—and gaining information about the child's profile relative to his or her strengths and weaknesses. To gather this information requires more than one test.

In my private clinical practice, our diagnostic evaluation core battery includes the following areas:

  • Receptive vocabulary—Dyslexics tend to have strengths in their understanding of oral vocabulary. We can use this measure to compare performance between other tests in other areas and determine where weak areas lie. This is also an important baseline measure to have. Early on, one’s vocabulary contributes to learning to read, but as kids get older, particularly 4th grade and on, reading contributes to vocabulary development. A child with dyslexia is at risk for falling behind his peers if he does not have access to (i.e., can’t read) the same information (texts) that his peers do. We want to ensure that a student’s vocabulary skills do not degrade over time, so it is important to get this baseline score early on to benchmark vocabulary growth.
  • Oral language skills—I have found that this important area is frequently overlooked in many evaluations. Oral language undergirds and is key to learning to read, spell, and write. Comprehension of spoken language tends to be an area of strength for individuals with dyslexia. While verbal expression is also generally an area of strength, we may find subtle differences in our dyslexics’ expressive language abilities, particularly in naming or word retrieval and/or in higher-level language skills, such as understanding inferences and gaining meaning from context.
  • Phonological processing skills—i.e., phonemic awareness, phonological memory, and rapid automatic naming. Difficulty in phonological processing is one of the hallmarks of dyslexia. Phonemic awareness has been shown to be highly predictive of reading success.
  • Reading—Depending on the age of the student, assessment of reading may entail letter identification and naming, letter-sound identification, whole word reading, nonsense word reading, passage reading including accuracy and fluency, and reading comprehension. In my practice, we give readers both a standardized passage-reading assessment and a timed real and nonsense word reading test. If a student is too young to get good information from a standardized reading test (i.e., he is not yet reading), then I give him either a criterion-referenced assessment that will give information as low as the pre-primer level or do an assessment of his book “reading” skills and book knowledge using a picture (i.e., wordless) book.
  • Spelling—This seems obvious, but what is of importance in a spelling assessment is not the standardized score, although that can be informative, but the types of errors being made (e.g., phonological, orthographic, or both). It can be challenging to assess a young student given that he may not be spelling many words, but at a minimum I get some idea of his letter-sound inventory (i.e., understanding of the letters/letter combinations and their corresponding sounds).
  • Writing—This is a tricky one because I have found that the standardized writing measures do not always reliably pick up on the challenges that my dyslexic clients seem to have. Many times, the scores that my clients receive on standardized writing tests are inflated. It really takes clinical knowledge and experience to analyze a writing sample. Many of the standardized tasks used to measure writing are contrived and do not assess all the various demands and genres of writing required in school. Here is when it is helpful to get some writing samples that have been done in school.
  • Short-term and working memory—If there is indication in the case history or during testing that memory issues are playing a role, then these areas need to be assessed.
  • Expressive vocabulary—Similarly, if there are concerns that the student has word retrieval or naming difficulties, this area should also be addressed in the assessment. Naming/word retrieval difficulties are of note because research has shown oral word retrieval problems can impact written language.

I have a fairly comprehensive piece that explains what making a diagnosis entails here. Additionally, I have quite a few of the tests for these areas listed here.

Once these areas have been assessed and the data interpreted (it is more than the test scores that informs the diagnosis), a pattern of strengths, usually in spoken language comprehension and use, and subsequent weaknesses in phonological processing and written language (i.e., decoding, fluency, comprehension, spelling, and/or writing) emerges; and the diagnosis of dyslexia can be made.