Evidence-Based Reviews

Autism: A three-step practical approach to making the diagnosis

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The term ‘autism’ covers a spectrum of developmental disorders that can be difficult to differentiate from other neurologic and psychiatric conditions. These experts describe the diagnostic process that works for them.


 

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Autism and related pervasive developmental disorders (PDD) are increasingly being identified in children—and even in some adolescents and adults. As a result, psychiatry now recognizes that these debilitating disorders are more common than was once believed, with a prevalence as high as 1 in 250.

An accurate diagnosis can help families take advantage of the variety of treatments being offered and investigated for affected individuals (Box).1 As psychiatrists who primarily see patients with autism and PDD, we recommend a three-step diagnostic approach that includes:

  • a comprehensive initial assessment to rule out medical or neurologic illnesses that can mimic or are associated with autism
  • differentiating PDDs from other psychiatric disorders with similar symptoms
  • distinguishing among the five PDD subtypes described in DSM-IV.2

Step 1: Comprehensive initial assessment

Assessment for possible PDD begins with a comprehensive history and examination. Most patients will be assessed in childhood, but milder symptoms of autism or Asperger’s disorder may go unrecognized initially and not be brought to a clinician’s attention until adolescence or even adulthood.

As PDDs are childhood-onset disorders, the logical approach emphasizes the developmental course and onset of symptoms. By definition, children with autism show evidence of the disorder by age 3. However, the diagnosis can often be made as early as age 18 to 24 months, when typically developing children exhibit a number of social and communicative milestones that are absent in autism.

History A thorough description of the mother’s pregnancy, labor, and delivery (if known) can help you determine whether intrauterine or perinatal events could be related to the patient’s presenting problem. These include infections and exposure to exogenous substances (e.g., alcohol) during the pregnancy, as well as complications during pregnancy and delivery (e.g., maternal bleeding, neonatal hypoxia).

A complete description of the child’s development including major milestones (e.g., sitting without support, walking, first words) can help distinguish among certain diagnoses and estimate the extent of developmental delay. Ask the parents what first concerned them about their child’s development, as children with autism most often present with delays in social or language milestones. Any developmental regression in acquired skills may implicate other neurologic processes and help distinguish among the subtypes of PDD.

Symptoms Review the symptoms of autism at length in all patients in whom you suspect a PDD. It is important to assess these symptoms in the context of the child’s overall developmental level. For example, a child with known mental retardation should be compared with peers of similar age and cognitive impairment.

Box

TREATMENT OPTIONS FOR AUTISM AND OTHER PDDS

Optimal treatment for autism and related pervasive developmental disorders (PDDs) involves the collaboration of many disciplines.

  • All school-aged children who are diagnosed with a PDD should be evaluated by the local school system to determine eligibility for special education. For those who are eligible, an individualized educational plan (IEP) is established to outline specific educational objectives and how they will be met. This IEP will often recommend speech therapy, occupational therapy, and social skills training.
  • Children with the disability of autism are guaranteed an appropriate education. Advocates are often available to assist parents in ensuring that their child’s educational needs are being met.
  • Many families also make use of treatment offered outside the school, such as speech and occupational therapy. In addition, behavioral psychotherapy based on principles of applied behavioral analysis is often helpful. Certain specialty clinics offer social skills training and additional supports for families. Parent support groups can also be a crucial source of information and support (“Related resources”).
  • Symptoms associated with autism such as aggression, irritability, hyperactivity, anxiety, and interfering repetitive phenomena may be reduced with appropriate psychopharmacologic treatment.2 In general, treatment is aimed at these associated target symptoms because no single drug treatment has been consistently shown to improve the core social and communication impairments.

Approximately 75% of persons with autism are diagnosed with mental retardation. A review of intellectual abilities and level of adaptive functioning can suggest the degree of mental retardation. A detailed family history is important because autism and other syndromes associated with mental retardation have varying degrees of heritability.

A thorough medical history, review of systems, and physical exam (with focus on the neurologic exam) can suggest the presence of medical conditions that could mimic or be associated with autism. The symptoms of autism are traditionally divided into three domains: social, communication, and repetitive behavior/narrow interests (Table 1):

  • Social impairment includes problems with nonverbal behaviors such as eye contact, facial expressions, and “body language;” failure to develop peer relationships; lack of spontaneous seeking to share enjoyment, interests, or achievements with other people; and lack of social or emotional reciprocity.
  • Communication impairment includes language delay, decreased communication with others, conversational impairment, echolalia, and lack of imaginative or social imitative play.
  • Impairments in behavior, interests, and activity take the form of all-encompassing preoccupations, “need for sameness” and compulsive rituals, motor stereotypies, and preoccupation with parts of objects.

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