Here's some information on assessment and some of the instruments you might encounter (or have already encountered online).
If you're an adult suspected of being at the high functioning end of the autism spectrum, such as possibly fitting Asperger's syndrome (AS), there are various problems that can occur when seeking diagnosis.
Choosing a specialist
Diagnosis is still very childcentric and the gold standard instruments, which were developed largely for classic autism, haven't been properly validated for adults with AS. Therefore, it's important to seek not only a specialist in autism (general psychiatrists and therapists are usually unequiped), but someone with experience in adult AS who understands and is honest about the use of instruments and how adults can present during interview.
Clinicians have found many adults with AS can appear relatively normal in structured conditions such as assessments. This is particularly the case for women. This could be the result of compensatory learning over a lifetime. It's only in the more complex environment of everyday life and through examining their developmental histories and self-reports that their disabilities might be apparent.
Before you agree to attend an assessment, ask a list of questions about the diagnostic process and their experience with adult AS in particular. Be aware of hidden agendas - for instance some clinics are focused more on research than patient care. If there's a heavy focus on genetic research it's possible they want to exclude many patients with milder AS to obtain more homogeneous research samples (that is, excluding the broader spectrum, which has become too heterogeneous for such research). They're likely to be making use of the ADI-R and ADOS instruments. These were developed largely for classic autism and exclude many adults with AS (I'll detail some research on this later). They're quoted as the gold standard instruments for assessing ASDs, but many professionals won't admit (or maybe are unaware of) their inadequacy for adult AS. There are still no comparable gold standard instruments for AS despite a deep need.
Preparation
Assessment can involve a battery of neuropsychological tests in conjunction with structured interviews. It can take several hours and sometimes more than a day. In some cases it only involves interviews and filling out questionnaires. Many clinicians require you bring childhood informants (usually parents) to be interviewed about your developmental history. Many adults for various reasons can't provide them. Some places will agree to assess you anyway, but make sure they'll be able to provide a diagnosis. There have been cases where patients were told the assessors could work around lack of childhood informants, but at the assessment they discovered the assessors wouldn't provide an actual diagnosis without them.
In preparation for assessment, list examples of your symptoms under each of the diagnostic criteria. Consider your entire development. It helps them assess you. Criteria can be found online. They usually use the DSM-IV (or almost identical ICD-10 in the UK) and sometimes the Gillberg criteria.
For questions based on the DSM-IV appropriate for adulthood, check out the Cambridge AAA instrument from here. Be aware it's not an established instrument and some criteria (mainly the imagination criteria) are only tentatively included.
In addition bring along your results for the AQ screening questionnaire, although they often administer this before or during assessment. The AQ and EQ are more discriminant than other questionnaires such as the SQ and the Reading the Mind in the Eyes test, which have greater overlaps with control groups.
There are also childhood questionnaires, scales and checklists online to cover your early development. If your parents can't attend the assessment or be interviewed by telephone you can obtain developmental information from them in this way. If they're completely unavailable (such as deceased or estranged) try to obtain records such as old school reports, medical records and home videos, or speak to others who knew you well in childhood.
Assessment
In addition to interviews and questionnaires on autism (and perhaps neuropsych tests including IQ), they should also give you a psychiatric interview and questionnaires to help with differential diagnosis and diagnosing comorbid conditions. Common comorbids are depression, anxiety (including a lot of social phobia symptoms in high functioning populations), OCD, ADHD, and personality disorders. Psychosis isn't too uncommon but some clinicians will rule out a diagnosis if you've had such an episode. Some will also adhere strictly to the other DSM-IV exclusion criteria and see clinically significant social phobia or ADHD symptoms as part of your autism, which is unhelpful because your treatment needs are more likely to be overlooked.
Diagnosis shouldn't be based on any one instrument, including the gold standard ones. If you're interviewed with the ADI-R and ADOS-G and are high-functioning, you're quite likely to not meet the threshold for ASD (see this recent Cambridge study). In the study, they took a group of adults with AS/high functioning autism. From that group, they found only about 64% met full ADI-R criteria, consistent with other studies (remember these intruments weren't developed for AS). They took this group (and those who'd only missed the ADI-R threshold by one point in one domain) and also administered the ADOS module 4 (which is for verbal adults). They found only 40% of the group reached the threshold for ASD. It was particularly poor at detecting ASD in high functioning women - only about 21% of the women who had AS/HFA met the cutoff. They suggest autistic women are more likely to compensate during adulthood and appear more socially typical - their ADI-R scores however (which cover early development) didn't differ from the males'.
The assessment should conclude with their diagnostic opinion and recommendations. Good clinicians will allow open discussion of both. If they don't or you have major concerns with their assessment or written report, be sure to address this to them in writing. This helps with quality control and leaves a papertrail.
This covers the basics. I might make further posts on features found more in AS than classic autism. I might also go into more detail on the screening questionnaires.
If you're an adult suspected of being at the high functioning end of the autism spectrum, such as possibly fitting Asperger's syndrome (AS), there are various problems that can occur when seeking diagnosis.
Choosing a specialist
Diagnosis is still very childcentric and the gold standard instruments, which were developed largely for classic autism, haven't been properly validated for adults with AS. Therefore, it's important to seek not only a specialist in autism (general psychiatrists and therapists are usually unequiped), but someone with experience in adult AS who understands and is honest about the use of instruments and how adults can present during interview.
Clinicians have found many adults with AS can appear relatively normal in structured conditions such as assessments. This is particularly the case for women. This could be the result of compensatory learning over a lifetime. It's only in the more complex environment of everyday life and through examining their developmental histories and self-reports that their disabilities might be apparent.
Before you agree to attend an assessment, ask a list of questions about the diagnostic process and their experience with adult AS in particular. Be aware of hidden agendas - for instance some clinics are focused more on research than patient care. If there's a heavy focus on genetic research it's possible they want to exclude many patients with milder AS to obtain more homogeneous research samples (that is, excluding the broader spectrum, which has become too heterogeneous for such research). They're likely to be making use of the ADI-R and ADOS instruments. These were developed largely for classic autism and exclude many adults with AS (I'll detail some research on this later). They're quoted as the gold standard instruments for assessing ASDs, but many professionals won't admit (or maybe are unaware of) their inadequacy for adult AS. There are still no comparable gold standard instruments for AS despite a deep need.
Preparation
Assessment can involve a battery of neuropsychological tests in conjunction with structured interviews. It can take several hours and sometimes more than a day. In some cases it only involves interviews and filling out questionnaires. Many clinicians require you bring childhood informants (usually parents) to be interviewed about your developmental history. Many adults for various reasons can't provide them. Some places will agree to assess you anyway, but make sure they'll be able to provide a diagnosis. There have been cases where patients were told the assessors could work around lack of childhood informants, but at the assessment they discovered the assessors wouldn't provide an actual diagnosis without them.
In preparation for assessment, list examples of your symptoms under each of the diagnostic criteria. Consider your entire development. It helps them assess you. Criteria can be found online. They usually use the DSM-IV (or almost identical ICD-10 in the UK) and sometimes the Gillberg criteria.
For questions based on the DSM-IV appropriate for adulthood, check out the Cambridge AAA instrument from here. Be aware it's not an established instrument and some criteria (mainly the imagination criteria) are only tentatively included.
In addition bring along your results for the AQ screening questionnaire, although they often administer this before or during assessment. The AQ and EQ are more discriminant than other questionnaires such as the SQ and the Reading the Mind in the Eyes test, which have greater overlaps with control groups.
There are also childhood questionnaires, scales and checklists online to cover your early development. If your parents can't attend the assessment or be interviewed by telephone you can obtain developmental information from them in this way. If they're completely unavailable (such as deceased or estranged) try to obtain records such as old school reports, medical records and home videos, or speak to others who knew you well in childhood.
Assessment
In addition to interviews and questionnaires on autism (and perhaps neuropsych tests including IQ), they should also give you a psychiatric interview and questionnaires to help with differential diagnosis and diagnosing comorbid conditions. Common comorbids are depression, anxiety (including a lot of social phobia symptoms in high functioning populations), OCD, ADHD, and personality disorders. Psychosis isn't too uncommon but some clinicians will rule out a diagnosis if you've had such an episode. Some will also adhere strictly to the other DSM-IV exclusion criteria and see clinically significant social phobia or ADHD symptoms as part of your autism, which is unhelpful because your treatment needs are more likely to be overlooked.
Diagnosis shouldn't be based on any one instrument, including the gold standard ones. If you're interviewed with the ADI-R and ADOS-G and are high-functioning, you're quite likely to not meet the threshold for ASD (see this recent Cambridge study). In the study, they took a group of adults with AS/high functioning autism. From that group, they found only about 64% met full ADI-R criteria, consistent with other studies (remember these intruments weren't developed for AS). They took this group (and those who'd only missed the ADI-R threshold by one point in one domain) and also administered the ADOS module 4 (which is for verbal adults). They found only 40% of the group reached the threshold for ASD. It was particularly poor at detecting ASD in high functioning women - only about 21% of the women who had AS/HFA met the cutoff. They suggest autistic women are more likely to compensate during adulthood and appear more socially typical - their ADI-R scores however (which cover early development) didn't differ from the males'.
The assessment should conclude with their diagnostic opinion and recommendations. Good clinicians will allow open discussion of both. If they don't or you have major concerns with their assessment or written report, be sure to address this to them in writing. This helps with quality control and leaves a papertrail.
This covers the basics. I might make further posts on features found more in AS than classic autism. I might also go into more detail on the screening questionnaires.