Diagnosis of Asperger syndrome

Several factors complicate the diagnosis of Asperger syndrome (AS), an autism spectrum disorder (ASD). Like other ASD forms, Asperger syndrome is characterized by impairment in social interaction accompanied by restricted and repetitive interests and behavior; it differs from the other ASDs by having no general delay in language or cognitive development. Problems in diagnosis include disagreement among diagnostic criteria, controversy over the distinction between AS and other ASD forms or even whether AS exists as a separate syndrome, and over- and under-diagnosis for non-technical reasons. As with other ASD forms, early diagnosis is important, and differential diagnosis must consider several other conditions. Several factors complicate the diagnosis of Asperger syndrome (AS), an autism spectrum disorder (ASD). Like other ASD forms, Asperger syndrome is characterized by impairment in social interaction accompanied by restricted and repetitive interests and behavior; it differs from the other ASDs by having no general delay in language or cognitive development. Problems in diagnosis include disagreement among diagnostic criteria, controversy over the distinction between AS and other ASD forms or even whether AS exists as a separate syndrome, and over- and under-diagnosis for non-technical reasons. As with other ASD forms, early diagnosis is important, and differential diagnosis must consider several other conditions. Asperger syndrome is defined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) as a pervasive developmental disorder that is distinguished by a pattern of symptoms rather than a single symptom. It is characterized by impairment in social interaction, by stereotyped and restricted patterns of behavior, activities and interests, and by no clinically significant delay in cognitive development or general delay in language. Impairments must be significant, and must affect important areas of function, and the diagnosis is excluded if criteria are also met for autism. Intense preoccupation with a narrow subject, one-sided verbosity, restricted prosody, and physical clumsiness are typical of the condition, but are not required for diagnosis. The World Health Organization ICD-10 criteria are almost identical to DSM-IV: ICD-10 adds the statement that motor clumsiness is usual (although not necessarily a diagnostic feature); ICD-10 adds the statement that isolated special skills, often related to abnormal preoccupations, are common but are not required for diagnosis; and the DSM-IV requirement for clinically significant impairment in social, occupational, or other important areas of functioning is not included in ICD-10. Diagnosis of Asperger syndrome can be tricky as there is a lack of a standardized diagnostic screening for the disorder. According to the US National Institute of Neurological Disorders and Stroke, physicians look for the presence of a primary group of behaviors to make a diagnosis such as abnormal eye contact, aloofness, failure to respond when called by name, failure to use gestures to point or show, lack of interactive play with others, and a lack of interest in peers. The diagnoses of AS or high-functioning autism (HFA) are sometimes used interchangeably; the same child can receive different diagnoses depending on the screening tool and the individual administering the test. Diagnoses may be influenced by non-technical issues, such as availability of government benefits for one condition but not the other. Advocacy and parent support organizations have proliferated around the concept of AS, and there are indications that this has resulted in more frequent diagnoses of AS, which may be given as a 'residual diagnosis' to children of normal intelligence who do not meet diagnostic criteria for autism but have some social difficulties.Underdiagnosis and overdiagnosis are problems in marginal cases; the increasing popularity of drug treatment options and the expansion of benefits has given providers incentives to diagnose ASD, resulting in some overdiagnosis of children with uncertain symptoms. Conversely, the cost of screening and diagnosis and the challenge of obtaining payment can inhibit or delay diagnosis. Developmental screening during a routine check-up by a general practitioner or pediatrician may identify signs that warrant further investigation. This will require a comprehensive team evaluation to either confirm or exclude a diagnosis of AS. This team usually includes a psychologist, neurologist, psychiatrist, speech and language pathologist, occupational therapist and other professionals with expertise in diagnosing children with AS. Observation occurs across multiple settings; the social disability in AS may be more evident during periods when social expectations are unclear and children are free of adult direction. A comprehensive evaluation includes neurological and genetic assessment, with in-depth cognitive and language testing to establish IQ and evaluate psychomotor function, verbal and nonverbal strengths and weaknesses, style of learning, and skills for independent living. An assessment of communication strengths and weaknesses includes the evaluation of nonverbal forms of communication (gaze and gestures); the use of non-literal language (metaphor, irony, absurdities and humor); patterns of speech inflection, stress and volume; pragmatics (turn-taking and sensitivity to verbal cues); and the content, clarity and coherence of conversation. Testing may include an audiological referral to exclude hearing impairment. The determination of whether there is a family history of autism spectrum conditions is important. A medical practitioner will diagnose on the basis of the test results and the person's developmental history and current symptoms. Because multiple domains of functioning are involved, a multidisciplinary team approach is critical; an accurate assessment of the individual's strengths and weaknesses is more useful than a diagnostic label. Delayed or mistaken diagnosis is a serious problem that can be traumatic for individuals and families; diagnosis based solely on a neurological, speech and language, or educational attainment may yield only a partial diagnosis. Advances in genetic technology allow clinical geneticists to link an estimated 40% of ASD cases to genetic causes; in one study the diagnostic yield for AS, PDD-NOS and atypical autism was similar to that for classic autism. Genetic diagnosis is relatively expensive, and genetic screening is generally impractical. As genetic tests are developed several ethical, legal, and social issues will emerge. Commercial availability of tests may precede adequate understanding of how to use test results, given the complexity of the genetics. Parents of children with AS can typically trace differences in their children's development to as early as 30 months of age, although diagnosis is not made on average until the age of 11. By definition, children with AS develop language and self-help skills on schedule, so early signs may not be apparent and the condition may not be diagnosed until later childhood or even old age. Impairment in social interaction is sometimes not in evidence until a child attains an age at which these behaviors become important; social disabilities are often first noticed when children encounter peers in daycare or preschool. Diagnosis is most commonly made between the ages of four and eleven, and one study suggests that diagnosis cannot be rendered reliably before age four. Asperger syndrome can be misdiagnosed as a number of other conditions, leading to medications that are unnecessary or even worsen behavior; the condition may be at the root of treatment-resistant mental illness in adults. Diagnostic confusion burdens individuals and families and may cause them to seek unhelpful therapies. Conditions that must be considered in a differential diagnosis include other pervasive developmental disorders (autism, PDD-NOS, childhood disintegrative disorder, Rett disorder), schizophrenia spectrum disorders (schizophrenia, schizotypal disorder, schizoid personality disorder), attention-deficit hyperactivity disorder, obsessive compulsive disorder, depression, semantic pragmatic disorder, multiple complex developmental disorder and nonverbal learning disorder (NLD).