Dyslexia Screening Part 5: The Diagnostic Evaluation


This is the last in a series of blogs I am writing about how schools determine which children need remedial instruction and of those, which have dyslexia.


Dyslexia Screening Part 5 The Diagnostic Evaluation


You can find the preceding blogs through the bullets below:

● Introduction and overview, part 1 and part 2

● Finding those that need a careful look using a Universal screener.

● A second screening for those exhibiting any signs of dyslexia.


Dr Michael Hart coined a succinct description for this process.

“A preliminary procedure, such as a test of examination, to detect the most characteristic signs of a disorder that may require investigation.” 


Screening, whether it be universal, or dyslexia screening which follows universal, are both good first steps in Dr Hart’s mind. Today, I’m going to talk about the key components to a very thorough diagnostic evaluation, and why it is important. 


If you have read my previous blogs, you should be able to identify all these steps on the flowchart on page 17 of the NJ Dyslexia Handbook. We have arrived at the box in the bottom right-hand corner. It can take some time for a child to reach this point, so remember that a referral to the school district Child Study Team (CST) for a comprehensive evaluation can be made at any point, if a disability is suspected. 


This evaluation should identify the source of the child’s reading problem or problems, and provide a diagnosis of dyslexia or another learning deficit. This information then enables the child’s teacher, parent/guardian and the CST, to develop an Individualized Education Plan (IEP) for that student. If necessary, the child can be referred to a further specialist, such as an audiologist. 


Evaluations can appear surprisingly broad unless you realize what goes into  creating an accurate diagnosis. They can also involve a large team including some or all of the following:


● Teachers

● Speech and Language Pathologists

● Physiotherapists

● Educational Psychologists

● Social workers

● Neuropsychologists

● Private assessment specialists

● Other healthcare professionals


This can be expensive, which explains the need for an efficient multi-level screening process to avoid the diagnostic test if it is not warranted. 


We will consider the separate pieces below: 


Family History and Observations



Dyslexia runs in families, so it can be important to gather a history of learning difficulties in immediate family members, such as parents and siblings, but also grandparents, cousins, and aunts and uncles. 


Other relevant data includes the child’s birth and health history; illnesses, birth complications, development milestones and so on.


Observations of the child in the classroom setting are relevant too: Interactions with classmates, interest in and focus on physical and academic tasks, and motor control.


Skills Used to Diagnose Dyslexia


The correct function of a car depends on all its components working in harmony, and a failure in one can seriously impair its smooth running. Similarly, reading and writing require the integration of myriad skills, and a weakness in one or more can slow the entire process to a crawl. To accurately diagnose the problem it is necessary to isolate and test each one. Weaknesses in the skills selected here are common to a number of reading disorders, but can be particularly helpful for identifying those students with dyslexia. 


Cognitive Function




When we think of cognitive processing, the test that most often springs to mind is Intelligence Quotient, or IQ. An IQ score is generally included in the assessment test, and a large differential between the IQ score and a child’s reading ability is a good indicator of a specific learning deficit, such as dyslexia. Some caution is required though, as an insufficient difference can be a reason to deny the support services that would help a child achieve his or her potential.


Beyond IQ, the specific cognitive functions tested are processing speed, working memory, and memory span. None of these directly impact the narrow definition of dyslexia as a phonological (sound-processing) deficit, but they do all affect word recognition and comprehension abilities. Processing speed is assessed using timed tests of aural and visual perception, and how quickly that stimulus translates to an output function such as speaking a word, or identifying a letter or shape. 


Oral Language Skills



On the listening (receptive) side, these span a range from the ability to identify words in a continuous stream of speech, divide these words into syllables, and sub-divide those syllables into the individual units we call phonemes. The complement is the ability to speak and write expressively, characterised by the ability to order thoughts into coherent sentences, choose appropriate words, and output these words as syntactically and grammatically correct written language. 


Dyslexia is generally recognized as a low-level phonological deficit, affecting the segmentation of words, and the identification and storage of phonemes. This affects word recognition, comprehension, vocabulary, spelling and so on. Higher level skills, such as the ability to comprehend concepts, reorganize sentences and ideas, and pick up on nuances are often unaffected, and the function of the assessment is to isolate any problems to specific areas. 


Some students will exhibit more than one deficit, such as challenges with directionality (left, right, up, down,) sequencing or word recall along with, say, dyslexia.


Oral language assessment generally starts at the sentence level, with observations of the child’s ability to interact in normal conversation.  More objective tests to assess comprehension and expression may involve listening to a passage and then answering questions. 


Though included within oral language skills, the low level tests of phonological skills are generally tested separately, as described below. 


Phonological and Phonemic Awareness


Phonological awareness is the ability to identify individual words in a sentence, which can be more difficult than you might think. Listen to a fluent speaker for any language you do not know, and you will probably hear it as a continuous stream rather than discrete words. Underpinning phonological awareness is the ability to segment words into syllables and syllables into individual phonemes. 


Since dyslexia is at its core a phonemic deficit, this is a key evaluation for diagnosis. 


Testing usually takes the form of listening to and then repeating, blending, or manipulating phoneme sequences. For example, say “sat” without the /s/, or change the middle sound in “hate” to an /ē/, or identify which sound changes between /h/ /ă/ /t/ and /h/ /ǒ/ /t/.


Nonsense words are usually used for these tests, to prevent the student guessing at the word. 


Word Recognition 


This assessment tests the student’s ability to recognize words in isolation, without the context or picture clues they normally encounter in books. The test will use lists of words of increasing length and difficulty.




Students with dyslexia can find it a challenge to learn the many grapheme↔phoneme relationships in English. Fluent reading requires them to identify these graphemes, run through the possible phonemes they represent, and then blend them to make a word they can recognize.


In some ways the decoding assessment is similar to the word recognition tests, but these words will be grouped to assess how well the student applies each of the decoding rules. For example, how the sound of the letters ‘c’ and ‘g’ change when followed by the vowels ‘e’, ‘i’ or ‘y’, or the way that a final silent-e affects the preceding vowel.


Generally the test will include nonsense words to avoid the student using vocabulary knowledge to inform the use of decoding rules.  


Orthography/Spelling (Encoding) 


Humans have been speaking far longer than we have been writing, so words in our minds are stored in phonemes. To write a word requires recalling the phonemes, then converting those to letters or groups of letters (ch, dge,) that comply with the spelling rules, and morphological rules (to, too or two,) and historical rules (high, but not hight,) and grammatical rules, and then record that as letters, all without forgetting the rest of the sentence we wished to convey! 


Add in the challenges of dyslexia, with confusion at the phoneme level, and any motor control and sequencing weaknesses, and you can begin to see how this can be a laborious process. 


This is usually assessed, by asking the student to write the alphabet, and spell some regular and irregular words, and then analyzing the errors for information on gaps in orthographic and phonic knowledge. 


Automaticity/Fluency Skills 


Dyslexia is quite often accompanied by (the medical term is ‘comorbid with’) slow processing. This is a real measurable condition, evaluated using the time to respond to visual or auditory stimuli. For example responding to instructions, or simply naming an array of letters or objects as quickly as they can. In fact, naming speed, especially letter or object naming, which can be performed at an early age, is one of the best predictors of later reading difficulties. 


Reading Comprehension


Reading comprehension can only be tested, obviously, if the student can read with reasonable fluency, and the passage includes mostly familiar vocabulary, and is at their grade level. One of the hallmarks of dyslexia is a substantial difference between the students aural and reading comprehension. Expert readers might be expected to achieve higher scores on the reading part, since they will automatically re-read anything that does not make sense. For dyslexic students the reverse is generally true. They are usually accomplished listeners, but reading strains their working memory capacity as they labor to decode, and pay attention to grammatical and punctuation cues. 


Tests usually involve reading and answering questions on familiar and unfamiliar topics, at the level of sentences and paragraphs, and then answering comprehension questions. It can also be instructive to compare their silent reading comprehension with their oral reading, and to record additional data such as oral reading speed and accuracy, ability to detect and self-correct errors and lost meaning. 


Written Expression


This is perhaps the most challenging area for students with dyslexia as it requires mastery of many skills to be successful. These include legible handwriting, fluency, spelling, grammar which includes syntax (the correct order of words), punctuation, vocabulary, and paragraph writing. A writing sample can tell you a lot and observing how a student writes may lead to a referral to a occupational therapist for remediation. 


Social-Emotional/Behavioral Functioning


This area is often assessed using behavioral checklists, clinical interviews and observations, and sometimes projective measures, which use ambiguous stimuli to give clues to a child’s personality.  


Dyslexia can often occur alongside learning disorders that impact the the social and emotional well being of a student, such as Attention-Deficit-Hyperactivity-Disorder (ADHD.)


In many of these comorbid instances the student may need to undergo further testing to properly understand their situation. 




A comprehensive evaluation is expensive in time and resources, and as such is only requested for those children about whom developmental concerns, and results from two levels of screening, strongly indicate dyslexia or another specific learning difficulty. 


The purpose of this evaluation is to gain insight into the specific weaknesses that hinder the normal development of reading and writing. 


The output from the evaluation should be a diagnosis, and an Individualized Education Plan to help them achieve their potential. 


If you are looking for more information on the extensive range of tests available on the market today, the University of Michigan maintains an impressive list on its Dyslexia Help web pages.




I would like to thank Dr Michael Hart for supporting me through the process of writing this blog, with his own ideas and resources. I encourage you to explore his web site, which is a treasure trove of information about diagnostic tests, testing and resources to support the dyslexic community. 


I also highly recommend The New Jersey Dyslexia Handbook which provides a wealth of information, check lists and flow-charts to guide you through the labyrinth of dyslexia and literacy development. 




Lorna Wooldridge is a dyslexia specialist tutor with over twenty-five years of experience and qualifications in the field of learning differences, from both the UK and USA. Lorna has a unique perspective on this condition as she has dyslexia, and her passion is to serve this community in any way she can.


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