Assessment Instruments for Asperger Syndrome

Howlin, P. (2000) Child Psychology & Psychiatry Review 5, (3) 120-129.

This review describes the current situation with regard to diagnostic instruments for Asperger’s syndrome. The paucity of such instruments, and the lack of adequate standardisation data amongst the few that do exist, represent a serious omission for both clinicians and researchers. The major problem limiting the development of effective diagnostic or screening instruments is the confusion inherent in ICD-10 and DSM-IV systems in differentiating autism from Asperger syndrome. In the absence of clear and clinically satisfactory diagnostic criteria, efforts to develop valid assessment instruments may be attempting to put the horse before the cart!

Clinicians, understandably confused by all this conflicting evidence, have tended to adopt their own working definitions, with variable degrees of consistency.

Given the persisting confusion as to what Asperger syndrome actually is, it is hardly surprising that very few diagnostic instruments have been designed specifically to identify it.

Conclusions
Despite the fact that the recent figures form the National Autistic Society, London (1997) and data based on Wing (1993) and Elhers and Gillberg (1993) suggest that Asperger syndrome may be much more common than autism, there are no adequately standardised diagnostic instruments specifically designed for this client group.

First, the few that do exist still require further research if they are to demonstrate acceptable levels of validity, reliability, specificity and sensitivity. Moreover, these are mainly being developed as screening instruments only.

Second, it is unrealistic to assume that a single instrument, no matter how thoroughly researched, can be used in isolation to ascertain diagnosis. Detailed information on cognitive and linguistic levels, family history, medical, social, psychiatric and, if possible, genetic background will also be required in order to differentiate similar conditions that may result from different causes.

Finally, there can be little doubt that, at least in part, ‘the absence of replicable, reliable, and valid instruments in this area is related to the absence of clear diagnostic criteria for these disorders’ (Lord, 1997). Unless problems of classification can be satisfactorily dealt with in future revisions of ICD and DSM, the development of effective and reliable diagnostic instruments will continue to be compromised.