As long as the diagnosis of autism is based on behaviour, a definitive pronouncement can only be made with hindsight. Perhaps, once a biological test is available, the diagnosis can be made before birth, but such a test still seems far in the future. Having to rely on behavioural criteria means having to live with ambiguity. And because the range of differences between all children is so large, even experienced clinicians can make misjudgements when pressed for a categorical pronouncement too early.
However, there is a dilemma. Researchers asked the question: if a child is diagnosed at the age of 24 months, how certain is the diagnosis? Researchers investigated how likely it is that the diagnosis is confirmed two years later. They showed that in the majority of cases the diagnosis was indeed confirmed, but still one-third of the cases were eventually not considered autistic. The study also showed that there is almost complete certainty about the diagnosis when the child is older than 30 months.
Many people feel that despite the risk of false alarms, early diagnosis is a desirable aim. One interesting solution to the problem is to proceed in two stages. At the first stage, around the age of 18 months, there could be screening for all children. At the second stage, perhaps around 30 months, a full diagnostic assessment could be offered to those children who had raised concerns. In fact, a screening instrument has already been developed. Three signs are assessed. First, does the child show ‘joint attention’, such as pointing with a finger. Second, is he or she following an adult’s gaze. Third, does he or she engage in simple pretend play?Most typically developing children aged 18 months can master these things.Most autistic children can’t. However, a number of children who apparently show these key behaviours nevertheless later go on to have an autistic disorder. This is likely to be Asperger syndrome.
许多人认为，尽管存在误报的风险，但尽早诊断是明智的目标。 解决这个问题的一种有趣方法就是分两个阶段进行。 在第一阶段，大约在18个月大时，可以对所有儿童进行筛查。 在第二阶段，大约30个月左右，可以对那些疑似儿童进行全面的诊断评估。 实际上，已经开发了一种筛选工具。用于评估三个迹象：
大多数发育正常的孩子在18个月时都能掌握这些技能。大多数自闭症儿童则不能。 然而，许多看起来表现出这些关键行为的儿童后来仍患上了自闭症。 这很可能是阿斯伯格综合症。