New Zealand Autism Spectrum Disorder Guideline - Ministry of Health

Part 1: Diagnosis and initial assessment of ASD
1.2.b Young people and adults
Components of diagnostic assessment
The diagnostic team and sources of
diagnostic assessment
Interagency or multidisciplinary assessments
or both are recommended for young people
11 33
and adults suspected of having an ASD
39-42
(Recommendation 1.2.2). Although it is
possible for a single clinician with experience
evaluating ASD to make a diagnosis in very
young children, assessment and diagnosis by a
team of health care practitioners experienced in
ASD is recommended for older individuals 33 . In
New Zealand, recommendations and proposals
have been made for the development of
specialist ASD services which could undertake
this role for people with ASD of all ages 43-45 , but
they have not been implemented.
Diagnostic assessment for young children
has been outlined in section 1.2.a. A similar
assessment should be undertaken for young
people and adults 33 46 . Diagnosing people
from these age groups presents a number of
challenges, however, which include:
• recognising the wide range of expression of
the symptoms of ASD which are influenced
by the person’s level of maturity, lifetime
experiences and cognitive ability 38
• the likelihood of more complex differential
diagnosis because of the increasing possibility
of alternative diagnoses and co-morbid
conditions 46
• competing diagnoses which may overshadow
ASD
Part 1
Currently, within New Zealand, there is no
formal referral pathway for ASD assessment
and diagnosis of adults. In some areas, referral
pathways for young people are also unclear
(Recommendation 1.2.3). Private health care
practitioners are often approached to carry
out diagnostic assessments. The health care
practitioners most likely to be able to diagnose
ASD in young people and adults include clinical
psychologists, educational psychologists, child
and adolescent psychiatrists and adult mental
health psychiatrists (Recommendation 1.2.2).
However, not all health care practitioners
have expertise in ASD, and identifying ASDcompetent
health care practitioners able to
diagnose older adolescents and adults is an
ongoing issue. When seeking a practitioner or
team to undertake a diagnostic assessment,
the choice of health care practitioner should be
based on their post-qualification education and
areas of specialisation, and recommendations
from within the ASD community (Good Practice
Point 6.26, Professional learning and development).
A suggested pathway for the identification and
assessment process for young people and adults
who may have ASD is outlined in Figure 2
which can be found at the end of this section.
• difficulty obtaining accurate and detailed
early developmental history as the age of the
individual increases 19 38 .
Research and expert opinion support diagnostic
assessment that includes the following
components:
• detailed health, developmental and
behavioural history (usually from parents
and other informants)
• detailed assessment of patterns of skills,
disabilities and behaviours
• comprehensive record and file review
• medical evaluation
• social and emotional abilities and interactions
• direct evaluation of the person through
interview and observation in a range of
environments
• formal assessment of intellectual functioning,
in order to better understand the person’s
abilities and their prognosis, but not as a
diagnostic tool in itself
New Zealand Autism Spectrum Disorder Guideline 51