The implications of different approaches to evaluating intervention: evidence from the study of language delay/disorder.

There is a pressure to both identify and expand the evidence base with regard to the treatment of speech and language disorders in children, as there is in other areas of speech and language therapy. This paper addresses two sources of evidence, a systematic review and meta-analysis of early language interventions and the monitoring of an early language target for socially disadvantaged children in Sure Start programmes in England. There is a growing number of efficacy studies in the field of speech and language disorders in children. For example, in a recent review for the Cochrane Collaboration in the UK 36 articles reporting a total of 33 different trials. Twenty-five of these articles provided sufficient information for use in a series of meta-analyses. The results indicate that speech and language therapy may be effective for children with phonological or expressive vocabulary difficulties. There is mixed evidence concerning the effectiveness of intervention for children with expressive syntax difficulties and little evidence available considering the effectiveness of intervention for children with receptive language difficulties. No significant differences were found between interventions administered by trained parents and clinicians. A number of gaps in the evidence base are identified. But such reviews are essentially retrospective and, while the results may be interesting for practitioners, they do not provide the whole picture. The paper then turns to a very different data set and the role of population monitoring, an approach to assessing the value of interventions which has not hitherto been used in any area of speech and language therapy. The data are derived from a year-on-year monitoring of the language output of 2-year-olds in Sure Start programmes in England. This is a programme funded by central government in the UK to reduce the impact of social disadvantage on children, parents and their communities. The practice and policy implications of these two different sources of information are considered. Who is the consumer of such information and what can they do with it once they have it?