The Role of Medical (including Psychiatric) Evaluations in the Diagnosis of ASD:from Gold-Standard Instruments to Full Diagnosis

Background: The diagnosis of ASD is based on observable behaviors. Best–estimate clinical diagnosis of ASD refers to a diagnosis of the clinical symptoms and development compatible with an ASD diagnosis with all available information including developmental history, assessment of ASD-behaviors, medical and school reports, with or without instruments developed for the assessment of parts of the diagnostic procedure (i.e. developmental history, ASD symptoms). Differential diagnosis of other psychiatric conditions that may better explain the observed behaviors should always be part of the diagnostic procedure.

Objectives: To present data from an “ASD Complex Diagnosis Program” where a full psychiatric evaluation is conducted in addition to a full ASD-related evaluation in cases in diagnostic doubt after a general Child Psychiatrist and/or Neuropaediatrician evaluation.

Methods: 180 patients consecutively attended in a Specialized consultative care (Tertiary Tier) Child Psychiatry Program for the assessment of children and adolescents with the suspicion of having an ASD diagnosis, underwent a full psychiatric and developmental evaluation. Final best-estimate diagnosis following DSM/ICD criteria was reached after i) evaluation of all life-time medical, educational and psychological reports ii) full psychiatric history with the patient and primary carer iii) full developmental history with the primary carer (roughly 50 % of the times with the ADI-R) iv) ADOS-2 evaluation v) psychopathological assessment including mental state vi) cognitive/language assessment if not available vii) family and teacher questionnaires for the assessment of ASD-behaviors, particularly in relation with peer-relationships vii) other questionnaires as appropriate viii) medical specialists consultation when indicated.

Results: main reasons for referral were: young children referred for a differential diagnosis with Specific Language Disorder, Intelligence Developmental Disorder or emotional and/or behavioral disorders; children/adolescents with multiple previous diagnoses; adolescents for differential diagnosis with psychotic disorders or personality disorders. 85 % of the patients were male; 78 % were up to 9 years of age and 22 % were 10-18 years old. Roughly 50 % were elegible for module 3 of the ADOS-2 (complex language level and up to early adolescence). There was a deviation to the left in the distribution of IQ, with 51 % of the patients having a below average IQ (<70). 80 % of the full sample was given an ASD diagnosis. However, among children/adolescents 8-15 years of age only 58% were given a diagnosis of ASD; behavioural disorder (including severe ADHD), social communication disorder and specific language disorders followed in frequency. Among adolescents 16-18 years of age, 62 % were diagnosed with an ASD, followed by other psychiatric disorders (high-risk of psychosis, personality disorders) and specific language disorders.

Conclusions: a full psychiatric evaluation seems to be an important add-on for the proper diagnosis of children and adolescents with complex developmental/behavioral difficulties.