Table 2.

Red flags indicating possible autism spectrum disorder.^*

Pre-school children
Communication impairment	Delayed or absent speech Deficient nonverbal communication e.g. lack pointing, difficulty following a point
Social impairment	Lack of response to others’ facial expression/feeling Lack of pretend play; little or no imagination Lack of showing typical interest in or play near peers purposefully Lack of initiation of activity Inability to share pleasure
Impairments of interests, activities and/or behaviors	Unusual or repetitive hand and finger mannerism Liking sameness/inability to cope with change Repetitive play with toys (eg, lining up toys; turning lights on and off)
School-age children
Communication impairment	Abnormalities in language development including muteness Persistent echolalia Unusual vocabulary for child’s age/social group
Social impairment	Inappropriate attempts at joint play (eg, may manifest as aggressive or disruptive behavior) Lack of awareness to classroom ‘norms’ (criticizing teachers, unwilling to cooperate in classroom activities)
Impairments of interests, activities and/or behaviors	Lack of flexible cooperative imaginative play/creativity Inability to cope with change Presence of odd behaviors including unusual response to sensory stimuli
Adolescents:
Language, non-verbal skills and social communication	Problems with communication, even if wide vocabulary and normal use of grammar. May be unduly quiet, may talk at others rather than hold a to-and-fro conversation, or may provide excessive information on topics of own interest. Unable to adapt style of communication to social situations (eg, may sound like ‘a little professor’ (overly formal) or be inappropriately familiar. May have speech peculiarities including ‘flat’, unmodulated speech, repetitiveness, use of stereotyped phrases. May take things literally and fail to understand sarcasm or metaphor. Unusual use and timing of non-verbal interaction (eg, eye contact, gesture and facial expression)
Social problems	Difficulty making and maintaining peer friendships, though may find it easier with adults or younger children. Can appear unaware or uninterested in peer group ‘norms’, may alienate by behaviors which transgress ‘unwritten rules’. May lack awareness of personal space, or be intolerant of intrusions on own space.
Rigidity in thinking and behavior	Preference for highly specific, narrow interests or hobbies, or may enjoy collecting, numbering or listing. Strong preferences for familiar routines, may have repetitive behaviors or intrusive rituals Problems using imagination e.g. in writing, future planning. May have unusual reactions to sensory stimuli (eg sounds, tastes, smell, touch, hot or cold.

^*From the Scottish Intercollegiate Guidelines Network (SIGN) 98.⁴⁵