Autism is a pervasive developmental disorder defined behaviorally and characterized by impairments in three areas: social interactions, reciprocal verbal and nonverbal communication and the range of interests and activities (1). Although recognition of this disorder may have its origins in Jean-Marc Gaspard Itard´s description of the „wild boy of Aveyron” from 1801 (2), the first formal account of autistic individuals was published by Leo Kanner in 1943 (3). The current definition of autism, although consistent with the deficits observer in Kanner´s original group of children, has been refined and broadened. Nowadays, persons with autism are considered to have one of the neurodevelopmental disorders that have such wide range of behavioral consequences and severity that they are collectively referred to as pervasive developmental disorders (PDDs) in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders, Text Revised (1). Within the group of five pervasive developmental disorders, a narrower term of autism spectrum disorders (ASDs) is used to refer to: autistic disorder, Asperger´s disorder and pervasive developmental disorder – not otherwise specified. In this article I will use the term „autism” and „autistic” broadly to refer to the whole range of ASDs.

Autism seems to affect more children than was previously believed. Early epidemiological studies report the prevalence of this disorder to be 4 children with autism in 10000 children in the general population (4), but some recent research suggested it to be 10 to 15 children with autism in 10000 (5). Frombonne (6, 7) reports the prevalence of ASD in children under the age of 8 years to be of the order of 60 per 10000 children. In the last decade, the number of children with ASD served in the United States has increased more than 1000% (8). Several factors could have contributed to an increased prevalence of autism. Existing data are insufficient to determine if there has been a true increase in incidence (2). Much of the reported increase in prevalence of autism and related disorders is probably attributable to improved detection and changes in diagnostic criteria (9). Regardless of the underlying reasons, recent evidence that the prevalence of diagnosed ASDs is increasing and that early diagnosis and intervention are likely associated with better long-term outcomes (10, 11) has made it imperative that pediatric primary health care providers have adequate knowledge regarding various issues related to disorder. Specifically, early detection of autism is currently a topic of much interest (12). The survey of professional attitudes by Skellern, Schluter and McDowell (13) draws attention to the increasing pressures placed on pediatricians and child psychiatrists to make a diagnosis of autism in response to the tide of applications for special education provision and disability allowance. Early identification and diagnosis enhances the opportunity for effective intervention; reduces parental stress by giving the family specific techniques and direction; and enables access to medical and other supports (14). Thus, in the current article, the focus is drawn to:

1) mechanisms of early diagnosis of autism and

2) the role of primary health care providers in the diagnostic process. It is important to note, however, that the guidelines presented in the paragraphs below are based on standards developed in the USA and in the United Kingdom. They may be difficult to implement right away in countries where systems of care for children with autism are still being developed. Nevertheless, they should be the goal to strive for.

Symptoms of autism typically occur during the first three years of life, yet the disorder often remains unrecognized and undiagnosed until or after late preschool age that is two or three years after symptoms became evident (15). In 1300 families surveyed by Howlin and Moore (16), the average age at diagnosis of autism was about 6 years, despite the fact that most parents felt something was wrong by 18 months of age and usually sought medical assistance by age 2 years. Fewer than 10% of the children were diagnosed at initial presentation; another 10% were either told to return if their worries persisted, or that their child „would grow out of it”. The rest were referred to another professional (at a mean age of 40 months), of which only 40% were given a formal diagnosis, 25% were told „not to worry”, and 25% were referred to a third or fourth professional. Almost 20% reported that they either had to exert considerable pressure to obtain the referrals or pay privately. Over 30% of parents referred to subsequent professionals reported that no help was offered, and only about 10% reported that a professional explained their child´s problems. Almost half of the families reported that the school system and other parents were the major source of assistance over time, rather than the medical health care community. This information is alarming considering the fact that primary care physicians have the opportunity to be the first point of contact when parents have concerns about their child´s development or behavior. The standard should be that the pediatrician recognizes the early symptoms of autism, facilitates the process of early detection of the disorder, and participates in its diagnosis and management.

Early diagnosis of autism requires two levels of investigation that are necessary to clinically identify children with this disorder (17, 18). Each level addresses a distinct component of patient management. The first level – „Routine Developmental Surveillance” -should be performed on all children and it involves first identifying those at risk for any type of atypical development, followed by identifying those specifically at risk for autism. The second level – „Diagnosis and Evaluation of Autism” – involves a more in-depth investigation of already identified children and differentiates autism from other developmental disorders.

Developmental surveillance is the routine monitoring and tracking of specific developmental milestones at check-up visits. This includes the gathering of information through reliable standardized instruments combined with parent and professional observations and judgment as well as tracking developmental progress as compared with children of similar age. Early detection is dependent on listening carefully to parents´ concerns about their child´s development and behavior. Current research has revealed that parents are usually correct in their concerns about their child´s development (19). Any concerns should be valued and should lead to additional investigation by the primary care pediatrician, a child neurologist, a developmental pediatrician or other qualified specialist, or preferably, a team of specialists. The child´s primary care provider should use during the first stage appropriate developmental screening questionnaires that provide sensitive and specific information. In the USA, for example, recommended screening instruments include The Ages and Stages Questionnaire, the Child Development Inventories as well as the Parents´ Evaluation of Developmental Status.

An indicator for immediate evaluation at level two is failure to acquire major developmental milestones. The following cases would be considered out of range of typical development: a child does not babble or point or use other gestures by the age of 12 months; a child does not use single words by 16 months or spontaneous (nonecholalic) 2-word phrases by 24 months; a child who experiences any loss of any language or social skills at any age (20). Deficits in joint attention differentiate infants with autism from those with typical development (21, 22, 23). These behaviors include deficits in the following areas: eye contact, orientation to name being called, pointing, and showing. In the toddler age group, a lack of pretend play and imitation, deficits in nonverbal communication, and disproportionate language delays differentiate autism from other developmental disorders. Although repetitive behaviors, stereotypic motor mannerisms, atypical sensory responses, and behavioral outbursts are generally observed in children with autism, these behaviors do not consistently differentiate autism from other developmental disorders at early ages (18).

Screening specifically for autism should be performed on all children failing routine developmental surveillance procedures using one of the validated instruments. Screening the population of children from birth through age 5 for ASD seeks to identify those children in the population most at risk of developing an ASD and/or developmental delay. The application of specific screening instruments for a particular disorder may occur at a specific age for the general population or when concerns and/or results of routine developmental surveillance indicate that a child is at risk for developmental difficulties. Screening instruments are not intended to provide diagnoses, but rather to suggest a need for further diagnostic evaluation and intervention planning assessment.

Within the past two decades, a variety of screening tools specific to ASD have been developed. The following instruments were selected based upon ease of use, time efficiency and acceptable psychometric properties and are recommended for use in primary care practice. Relevance of the instrument and demonstrated utility with very young children were also factors of primary importance in their inclusion. Currently accepted tools include the Checklist for Autism in Toddlers and the Pervasive Developmental Disorder Screening Test.

The Checklist for Autism in Toddlers (CHAT), a screening tool designed for use with 18-month-old children in primary care settings was developed in England and has been used to screen more than 16 000 toddlers (24, 25). Of the 14 items measuring various aspects of imitation, pretend play, and joint attention, nine are derived from parental history and five are from observation. There are five items in CHAT that are considered critical items. They deal with:

1) pretend play,

2) indicating interest,

3) joint attention,

4) play skills, and

5) referential pointing. In one study, all children failing these 5 critical items twice, 1 month apart, were later diagnosed with AD between 20 and 42 months old (14). Children with global delays are likely to also fail the CHAT and need additional investigation to rule out mental retardation. Finally, the CHAT has been demonstrated to have relatively poor sensitivity. A modified version is being tested to address this issue.

The Pervasive Developmental Disorders Screening Test-II (26) is a parent report measure designed to indicate the likelihood of global and pervasive developmental disorders in children from birth through 3 years of age. The scale consists of seventy-one true/false items, presented in six-month age intervals. Cutoff algorithms have been established for differentiating children with the likelihood of an ASD from children with other developmental challenges. Primary care physicians are encouraged to become familiar with at least one autism screening tool and perform it on all children. If this is not possible, then they should prompt referral to a specialist or a team of specialists.

Best practice procedures recommend that all children be screened specifically for ASD at ages 18 and 24 months. Screening at these two periods is recommended because most children who are later diagnosed with an ASD display symptomatology (excesses/atypical behaviors) and/or lack achievement of core developmental milestones by the second year of life. Current research literature suggests that a significant number of features of ASD are present by 18 months of age (14, 22, 27, 28, 29, 30), specifically, verbal and nonverbal communication deficits. In addition, since some children with ASD evidence regression in skills between 15 and 24 months, screening at age 2 years facilitates identifying these children as well.

Once a positive screen for ASD is obtained, the primary care provider or other referring professionals should routinely make a referral to an institution that specializes in diagnosing children with atypical development. This will ensure a timely, more fluid, family-centered diagnostic and assessment process.

A comprehensive, multidisciplinary assessment is required to evaluate a child for an ASD and to differentiate ASDs from other developmental disorders (17, 31, 32). Since there are no definitive diagnostic tests, a clinical diagnosis by an expert, based on DSM-IV, TR criteria, remains the gold standard of ASD diagnosis (33). The diagnostic evaluation for ASD necessarily includes six specific components:

1) review of relevant background information,

2) parent/caregiver interview,

3) comprehensive medical evaluation,

4) direct observation,

5) cognitive assessment, and

6) measures of adaptive functioning.