Autism Spectrum Disorder: Core Diagnostic Features

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder classically characterised by a triad of impairments: early onset, impaired communication, and restrictive/stereotyped behaviour. The correct combination is 1, 2 and 3.

Analysis of Each Statement

• 1. Onset before 3 years of age: Classical (ICD-10/DSM-IV) descriptions of Autistic Disorder require that abnormal or impaired development be evident before the age of 3 years, manifesting as delayed or abnormal functioning in social interaction, language as used in social communication, or symbolic/imaginative play. This is a correct core feature.
• 2. Impaired verbal and gestural communication: Qualitative impairment in communication — including delayed or absent spoken language, impaired ability to initiate or sustain conversation, and abnormal use of gestures/nonverbal behaviours (eye contact, facial expression, body postures) — is one of the two central diagnostic domains of ASD. This is a correct core feature.
• 3. Stereotypic and restrictive behavioural patterns: Restricted, repetitive, and stereotyped patterns of behaviour, interests, and activities (e.g., stereotyped movements, insistence on sameness, restricted interests) form the second central diagnostic domain of ASD. This is a correct core feature.
• 4. Tangential speech: Tangential speech (answers that drift off-topic and never return to the original point) is a formal thought disorder seen in conditions such as schizophrenia and other psychotic disorders, not a defining feature of ASD. Children with ASD may show echolalia, pronoun reversal, or lack of reciprocal conversation, but "tangential speech" as a described thought-disorder pattern is not part of the ASD diagnostic criteria. This statement is incorrect.

Why the Other Options Are Wrong

• 1, 3 and 4: Incorrectly includes tangential speech (not an ASD feature) while omitting impaired communication, which is one of the two essential diagnostic domains of ASD.
• 1, 2 and 4: Again incorrectly includes tangential speech and omits the essential criterion of restrictive/stereotyped behaviour patterns.
• 2, 3 and 4: Incorrectly includes tangential speech and omits the age-of-onset criterion, which is a defining element of the classical diagnosis.

Conclusion

The characteristic features of Autism Spectrum Disorder are onset before 3 years of age, impaired verbal and gestural (nonverbal) communication, and stereotypic/restrictive behavioural patterns — corresponding to statements 1, 2 and 3. Tangential speech is not a recognised feature of ASD.