Since the questionnaire relies on client self-report, all responses should be verified by the clinician, and a definitive diagnosis is made on clinical grounds taking into account how well the client understood the questionnaire, as well as other relevant information from the client.
The Autism-Spectrum Quotient (AQ) is not diagnostic, but may serve as a useful instrument in identifying the extent of autistic traits shown by an adult of normal intelligence. A score of 32+ appears to be a useful cut-off for distinguishing individuals who have clinically significant levels of autistic traits. Such a high score on the AQ however does not mean an individual has Asperger syndrome (AS) or high-functioning autism (HFA), since a diagnosis is only merited if the individual is suffering a clinical level of distress as a result of their autistic traits.
A limitation of this instrument is that it may not be appropriate for patients with low IQ, since the AQ assumes reading comprehension skills.