The early detection of autism in clinical practice

Abstract

utism is the prototypical form of a spectrum of related,complex neurodevelopmental disorders referred to asautistic spectrum disorders (ASDs; also known as the perva-sive developmental disorders; PDDs). In addition to autisticdisorder, the ASDs include Asperger syndrome, which is dis-tinguished by relatively strong cognitive and language skills,and PDD-not otherwise specified, a less severe variant ofautism (1,2). Like other complex neurodevelopmental disor-ders (eg, schizophrenia), ASD is thought to be the final com-mon pathway of multiple etiological (largely genetic) andneuropathological mechanisms (3), thus, complicating thesearch for universal, autism-specific biological markers. Inthe absence of a biological marker, ASD is defined behav-iourally, by impairments in three functional domains: social-ization; communication; and a lack of behavioural flexibility,with reliance on routines (1,2).Autism is among the most prevalent of the severe disor-ders of development. Health practitioners throughoutCanada and elsewhere are currently experiencing a stagger-ing increase in the numbers of children coming to atten-tion. Prevalence is now estimated at one to two per 1000 forautism, and six to seven per 1000 for the entire spectrum ofautistic disorders (4,5). While the issue of whether there isa real increase in ASD remains controversial (6,7), theincremental increase over time is generally attributed to thegradual broadening in how we define autism/ASD, and ourincreased awareness and detection of its diverse manifesta-tions, particularly in the more cognitively or linguisticallycapable child (4). The fact remains that individuals withASD are among the most difficult and costly to treat (8,9).The impact on families and their quality of life is enormousand sometimes devastating (10,11).Although prognosis for individuals with autism has his-torically been poor (12,13), recent evidence points toimproved outcomes with early intensive behavioural inter-vention (14-16). These interventions focus on the struc-tured and systematic teaching of targeted communicationand other functional skills, using empirically derived positivebehavioural principles. Evidence of treatment effectiveness,together with the increasing availability throughout Canadaof publicly funded early autism-specific intervention pro-grams, serves to underscore the critical importance of concerted efforts aimed at the earlier detection of ASDs(hereafter autism). At present, autism is typically not identi-fied before four years of age, often more than two years afterparents first seek medical attention (17). Initial contactsusually result in misplaced reassurance, followed by a seriesof professional consultations before a definitive diagnosis ofautism is made. The long delay frustrates parents and post-pones appropriate, autism-specific intervention.In an attempt to optimize early access to best practicesintervention, a panel of cross-disciplinary experts and par-ent representatives have recently issued practice guidelinesfor early community-based detection of autism (18). Theseguidelines have been adopted by the American Academiesof Pediatrics (19), Neurology (18) and Child andAdolescent Psychiatry (20), and after minor revisions,endorsed by several jurisdictions in Canada and the UnitedStates. Recommendations are that practitioners adopt atwo-stage early detection strategy: monitoring for signs ofautism within the context of routine developmental surveil-lance; and in cases of concern, followed by the use of an earlyautism screening instrument to identify children at highestrisk. Because there does not yet exist an ideal screeninginstrument for community use, practice guidelines areaimed at identifying infants/toddlers at high risk for autism,who can then be targeted for more comprehensive develop-mental assessment (18).Our purpose in this paper is to elaborate on this two-stage strategy, with a particular focus on its implementation.In this context, we outline what is currently known aboutthe early signs of autism and available screening instru-ments, and address concerns regarding false positive andequivocal cases. We end by commenting on the thoughtfulessays of parents that accompany this paper.CLINICAL MONITORING FOR EARLY SIGNS OF AUTISMAs a first step toward earlier detection, guidelines call forthe monitoring of early signs of autism during regular healthvisits as an adjunct to ongoing surveillance or monitoring ofdevelopment. Evidence on the early signs of autism deriveslargely from parents’ retrospective reports (21,22) and homevideos (23,24) of children later diagnosed with autism, andis thus limited by its retrospective and restricted nature(25). However, remarkable consistency exists between these