Commentary: The Modified Checklist for Autism in Toddlers

The question of when it is best to screen for autism may only be answered by a series of empirical studies. These will be difficult to plan, fund, and conduct, and will by necessity take many years because of the need to systematically follow up the whole cohort screened. In our study, we identified 19 of the 50 children with autism by their profile at the 18-month screen (though note that some fell out of risk status at the repeat screen 1 month later--thus sacrificing sensitivity for improved positive predictive power). Through the subsequent surveillance methods we employed, we identified the remaining cases as follows: 5 at 42 months, 4 between 42 months and 7 years, and 25 at 7 years. We do not mean to end on a pessimistic note. Our experiences have been positive both in regard to the instrument we developed and the effects that using it have had on the health practitioners involved in the research study. In discussion, practitioners have commented on the usefulness of knowing what prelanguage and prosocial skills can reliably be looked at during the 18-month check. Training using the CHAT and eliciting its behaviors improved the skills and confidence of primary health practitioners. It is our view that this has had the effect of reducing the age at which autism is recognized and cases are referred on for a developmental assessment. The work reported by Robins er al. makes an important contribution to this ongoing research and clinical process as we attempt to accurately identify children with autism at a young age.

A screening instrument for autism at 18 months of age: a 6-year follow-up study

OBJECTIVES

A population of 16,235 children aged 18 months was screened using the Checklist for Autism in Toddlers (CHAT) to identify childhood autism (CA). Two further screening procedures were conducted at age 3 and 5 years. The population was followed up at age 7 years in order to establish the sensitivity, specificity, and positive predictive value of the instrument.

METHOD

A brief checklist assessing joint attention and pretend play behaviors was administered by primary health care practitioners when the children were 18 months old. Follow-up methods included screening through parents and health practitioners and checking medical and educational records.

RESULTS

Nineteen cases of CA were successfully identified by the CHAT at 18 months. At follow-up a total of 50 cases of CA were identified via all surveillance methods. Thus, the CHAT has a sensitivity of 38% and a specificity of 98% for identifying CA. The positive predictive value of the instrument was maximized by concentration on the highest-risk group. Repeated screening 1 month later increased the positive predictive value to 75% for identification of CA but reduced the sensitivity to 20%, although the specificity was close to 100%. The screen also identified cases of pervasive developmental disorder as well as children with language and other developmental disorders.

CONCLUSIONS

The CHAT can be used to identify cases of autism and related pervasive developmental disorders at 18 months of age. It is emphasized that the CHAT is not a diagnostic instrument but can identify potential cases of autism spectrum disorders for a full diagnostic assessment.

Children with autism show local precedence in a divided attention task and global precedence in a selective attention task

Children with a diagnosis of autism and typically developing children were given two variations of the Navon task (Navon, 1977), which required responding to a target that could appear at the global level, the local level, or both levels. In one variation, the divided attention task, no information was given to children regarding the level at which a target would appear on any one trial. In the other, the selective attention task, children were instructed to attend to either the local or the global level. Typically developing children made most errors when the target appeared at the local level whereas children with autism made more errors when the target appeared at the global level in the divided attention task. Both groups of children were quicker to respond to the global target than the local target in the selective attention task. The presence of normal global processing in the children with autism in one task but not in the other is discussed in terms of a deficit in mechanisms that inhibit local information in the absence of overt priming or voluntary selective attention to local information.

Autism spectrum disorders at 20 and 42 months of age: stability of clinical and ADI-R diagnosis

The association between, and stability of, clinical diagnosis and diagnosis derived from the Autism Diagnostic Interview-Revised (ADI-R; Lord, Rutter, & Le Couteur, 1994) was examined in a sample of prospectively identified children with childhood autism and other pervasive developmental disorders assessed at the age of 20 months and 42 months. Clinical diagnosis of autism was stable, with all children diagnosed with childhood autism at age 20 months receiving a diagnosis of childhood autism or a related pervasive developmental disorder (PDD) at age 42 months. Clinical diagnosis of childhood autism was also reasonably sensitive, with all children who went on to receive a clinical diagnosis of childhood autism at 42 months being identified as having autism or PDD at 20 months. However, clinical diagnosis for PDD and Asperger's syndrome lacked sensitivity at 20 months, with several children who subsequently received these diagnoses at 42 months receiving diagnoses of language disorder or general developmental delay, as well as in two cases being considered clinically normal, at the earlier timepoint. The ADI-R was found to have good specificity but poor sensitivity at detecting childhood autism at 20 months; however, the stability of diagnosis from 20 to 42 months was good. In addition, the ADI-R at age 20 months was not sensitive to the detection of related PDDs or Asperger's syndrome. The continuity and discontinuity between behavioural abnormalities identified at both timepoints in the three domains of impairment in autism was examined, both in children who met final clinical criteria for an autistic spectrum disorder, and for children with language disorder who did not, as well as for a small sample of typically developing children.

Infants with autism: an investigation of empathy, pretend play, joint attention, and imitation

Systematic studies of infants with autism have not been previously carried out. Taking advantage of a new prospective screening instrument for autism in infancy (S. Baron-Cohen et al., 1996), the present study found that, compared with developmentally delayed and normally developing children, 20-month-old children with autism were specifically impaired on some aspects of empathy, joint attention, and imitation. Infants with autism failed to use social gaze in the empathy and joint attention tasks. Both the infants with autism and the infants with developmental delay demonstrated functional play, but very few participants in either group produced spontaneous pretend play. In the developmental delay group, but not the autism group, pretend play was shown following prompting. The implications of these findings for developmental accounts of autism and for the early diagnosis of the disorder are discussed.

Infants with autism: an investigation of empathy, pretend play, joint attention, and imitation

Systematic studies of infants with autism have not been previously carried out. Taking advantage of a new prospective screening instrument for autism in infancy (S. Baron-Cohen et al., 1996), the present study found that, compared with developmentally delayed and normally developing children, 20-month-old children with autism were specifically impaired on some aspects of empathy, joint attention, and imitation. Infants with autism failed to use social gaze in the empathy and joint attention tasks. Both the infants with autism and the infants with developmental delay demonstrated functional play, but very few participants in either group produced spontaneous pretend play. In the developmental delay group, but not the autism group, pretend play was shown following prompting. The implications of these findings for developmental accounts of autism and for the early diagnosis of the disorder are discussed.

Mood and physiological effects of subcutaneous nicotine in smokers and never-smokers

This study compared the effect of subcutaneous nicotine injections (2 x 0.3 mg and 2 x 0.6 mg) with saline on subjective and physiological measures in 18 never-smokers and 18 smokers (24-h nicotine deprived), under conditions of rest and cognitive testing. Prior to the injections the mood of the smokers had deteriorated to a level significantly below that of the never-smokers as a result of tobacco withdrawal. Cognitive tests caused reductions in calmness and increased alertness but there was no evidence of nicotine improving mood in either group under either condition. The 0.6 mg dose worsened mood in never-smokers and caused unpleasant symptoms (e.g. dizziness and arm pain) in both groups. Compared with smokers, never-smokers experienced stronger symptoms of nicotine toxicity and a greater reduction in alertness in response to the 0.6 mg dose, suggesting chronic tolerance to some nicotine effects in smokers. Nicotine produced similar increases in heart rate and decreases in finger pulse volume in both groups. Our results imply that if nicotine has a mood enhancing effect it occurs only after tolerance has been acquired to its primary adverse effects, and that its ability to reverse the mood deterioration caused by tobacco withdrawal is susceptible to situational factors such as our experimental conditions.

Cognitive performance effects of subcutaneous nicotine in smokers and never-smokers

In a double-blind placebo-controlled crossover study the effects of two doses of subcutaneous nicotine and saline were compared on a range of performance measures in 18 abstaining smokers and 18 never-smokers. Each subject received two injections (40 min apart) of saline, 0.3 mg nicotine, or 0.6 mg nicotine in a balanced order over three sessions. Performance was assessed before and after the injections on nine tests [news recall, Sternberg memory task, finger tapping, logical reasoning, rapid visual information processing (RVIP), long-term word recognition, digit recall, Stroop test, and critical flicker fusion threshold]. In the abstinent smokers, nicotine produced significantly faster correct responses on the logical reasoning test, more target hits, faster reaction times and improved sensitivity on the RVIP task, and more correct responses on word recognition. In never-smokers, nicotine produced faster reaction times on the RVIP and digit-recall tasks, although in the latter case this was at the expense of fewer correct responses. There were no significant differences between the two groups' responses to nicotine but smokers performed worse than never-smokers prior to injections, even controlling for background characteristics. These results are consistent with other recent research suggesting a primary effect of nicotine in enhancing cognitive performance.

Can children with autism be taught to understand false belief using computers?

A specially designed computer version of the Sally-Anne false task belief task was used to teach understanding of false belief to three groups: children with autism, children with Down's Syndrome and young normal children. In an initial assessment children were selected for teaching only if they failed four false belief tasks: the dolls version of the Sally-Anne task (close transfer task) and three other false belief tasks involving different scenarios (distant transfer tasks). Following teaching, all three groups were able to pass the Sally-Anne task, but the children with autism alone were unable to pass the distant transfer tasks. The possibility that the children with autism had developed an alternative strategy in order to pass the instruction task is discussed.

Psychological markers in the detection of autism in infancy in a large population

BACKGROUND

Investigation to see if there are key psychological risk indicators for autism in a random population study of children at 18 months of age; and to assess how well these discriminate children who receive a diagnosis of autism from other forms of developmental delay.

METHOD

Sixteen thousand children in the southeast of England were screened for autism by their health visitor or GP, during their routine 18-month-old developmental check-up, using the CHAT (Checklist for Autism in Toddlers). From a previous high-risk study we predicted that children at 18 months of age who failed three items ('protodeclarative pointing', 'gaze-monitoring', and 'pretend play') would be at risk for receiving a diagnosis of autism. From other evidence, we further predicted that those 18-month-olds who failed one or two of the key items (either pretend play, or protodeclarative pointing and pretend play) would be at risk for developmental delay without autism.

RESULTS

Twelve children out of the total population of 16,000 consistently failed the three key items. Of these, 10 (83.3%) received a diagnosis of autism. Thus, the false positive rate was 16.6% (2 out of 12 cases), and even these 2 cases were not normal. When the 10 children with autism were reassessed at 3.5 years of age, their diagnosis remained the same. Thus the false positive rate among the cases diagnosed with autism was zero. In contrast, of 22 children who consistently failed either protodeclarative pointing and/or pretend play, none received a diagnosis of autism, but 15 (68.2%) received a diagnosis of language delay.

CONCLUSIONS

Consistent failure of the three key items from the CHAT at 18 months of age carries an 83.3% risk of autism; and this pattern of risk indicator is specific to autism when compared to other forms of developmental delay.