As we move into 2013, it is a good time to reflect on the current state of the art of paediatric neuropsychology and assessment.
As a neuropsychologist doing some work in the community, an ongoing area of confusion and discussion that has been relevant for this private work is the accurate and valid assessment of learning and literacy disorders in children. This can often be confusing, as speaking to different experienced clinicians or researchers about this topic can yield different answers regarding the diagnostic criteria for a specific literacy disorder. Many times, the responses on exactly how to diagnosis such a developmental disorder are vague and sometimes even uncertain.
As I understand it, part of the reason for this ambiguity is that setting a diagnostic threshold for a literacy disorder, for example dyslexia, can be somewhat arbitrary, given that reading skill is a continuum, leading to some confusion in categorising ‘dyslexic’ from ‘not dyslexic’. The confusion widens when we discuss whether this diagnostic threshold should be relative to age or IQ expectations.
Traditional definitions have required that the reading deficits are significantly below the IQ level of the child. This the raises fundamental issue that IQ is correlated with measures of reading and spelling, in a way confounding the assessment and diagnosis. There is also the issue that there are many children who will not be diagnosed using this definition (even though their reading skill is well below age expectation and is interfering with their functioning) as their IQ is also at a low level. An interesting point made by Pennington (2009) is that if this was to remain our diagnostic definition, we would ironically be systematically excluding those that are arguably the most severe cases (those with low reading skill and low IQ).
Recent research has looked into the differences between IQ discrepancies and age discrepancies in diagnosing dyslexia. At this stage, it seems that maintaining a distinction between these two methods of diagnosis is hard to justify, given that there is no external validity for the distinction, and also that treatments appear to be just as efficacious for those with and without IQ discrepancies. Therefore, the current consensus is that children should be identified and treated with a specific reading disorder, or dyslexia, if they meet either definition.
The ongoing problem with both definitions remains that any chosen diagnostic threshold is arbitrary. Pennington (2009) argues that an age based discrepancy requires an age based standardisation score of 80 or lower (a 1.3 standard deviation cut-off). For an IQ based cut-off, the predicted reading score should be used, along with a chosen level of discrepancy from that predicted score. Pennington suggests that a discrepancy of 20 is used (again, a 1.3 standard deviation cut-off is employed). Therefore, a score which is 20 standardised points lower than the predicted reading score can be considered to be diagnostic.
Despite the diagnostic criteria surrounding literacy disorders (as well as other related language and numeracy disorders) becoming clearer with ongoing research, it still remains a grey area, with clinical judgement an important aspect of such an assessment. Importantly, this discussion is not to mention the evidence-based intervention for these literacy difficulties... a can of worms for another time.
We would be very interested to hear about views on this topic, and about your experiences in these types of assessment.
Wishing you all lots of success and good wishes for 2013.
Frank and Linda
References
Pennington, B.F. (2009). Diagnosing learning disorders: A neuropsychological framework (Second Edition). New York, Guilford Press.
Upcoming conferences
Abstracts close on Feb 15 for the INS meeting in Amsterdam (July 10-13 2013).
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