Screening and surveillance for autism and pervasive developmental disorders

Screening and surveillance are different but related activities involving the detection of impairments with a view to prevention or amelioration of consequent disability and handicap. Screening is the prospective identification of unrecognised disorder by the application of specific tests or examinations. Surveillance refers to the ongoing and systematic collection of data relevant to the identification of a disorder over time by an integrated health system. The review by Hall1 in Health for all children concluded that most screening tests that set out to identify neurodevelopmental disorders do not meet the stringent criteria outlined by Cochrane and Holland2 and Wilson and Jungner.3 In some conditions, for example language disorders, this is because there is uncertainty about “caseness” and tests tend to have low sensitivity and specificity.4 5 This is particularly the case for screening tests that attempt to identify a specific condition rather than general developmental delay, and for the identification of relatively rare disorders. In the latter case, even when the sensitivity and specificity of a screen remain constant, the positive predictive value (the proportion of children with a positive screen result and who have the disorder) is lower the rarer a disorder is within the population.6 The concept of developmental surveillance is a parent–professional partnership that takes a broader look at developmental and behavioural skills and progress over time. It combines the observations of parents with the developmental knowledge of the professional and the deployment of specific tests. There is evidence that the use of screening instruments in combination with asking parents about their concerns improves the efficiency of an instrument.7 8 However, the number and type of concerns that parents have about their child's behaviour and development determine whether using a screening instrument within the clinic setting is effective. For example, Glascoe, …