The review shows that overall there is a positive effect of speech and language therapy interventions for children with expressive phonological and expressive vocabulary difficulties. The evidence for expressive syntax difficulties is more mixed, and there is a need for further research to investigate intervention for receptive language difficulties. There is a large degree of heterogeneity in the results, and the sources of this need to be investigated.

A meta-analysis was carried out of interventions for children with primary developmental speech and language delays/disorders. The data were categorized depending on the control group used in the study (no treatment, general stimulation, or routine speech and language therapy) and were considered in terms of the effects of intervention on expressive and receptive phonology, syntax, and vocabulary. The outcomes used in the analysis were dependent on the aims of the study; only the primary effects of intervention are considered in this review. These were investigated at the level of the target of therapy, measures of overall linguistic development, and broader measures of linguistic functioning taken from parent report or language samples. Thirty-six articles reporting 33 different trials were found. Of these articles, 25 provided sufficient information for use in the meta-analyses; however, only 13 of these, spanning 25 years, were considered to be sufficiently similar to be combined. The results indicated that speech and language therapy might be effective for children with phonological or expressive vocabulary difficulties. There was 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 those administered by clinicians. The review identified longer duration (>8 weeks) of therapy as being a potential factor in good clinical outcomes. A number of gaps in the evidence base are identified.

The editors have tried to ensure the accuracy of this report but cannot accept responsibility for any errors or omissions. They would like to thank the referees for their constructive comments on the draft document.

Screening young children for developmental conditions such as speech and language delay is considered to be a part of the Child Health Surveillance programme in the UK. It is currently practised in many different ways throughout the country and like screening for other conditions conventionally identified in infancy, has been the subject of some concern for those responsible for providing such services. This systematic review (Law et al. 1998) was hypothesis driven and aimed to: i) establish whether, given the available evidence, there was sufficient evidence to warrant the introduction of universal screening for speech and language delays in children up to seven years of age; ii) identify gaps in the available literature; iii) identify priority areas in need of further investigation and iv); provide evidence-based recommendations for the future provision of services.

The prevalence and the natural history of primary speech and language delays were two of four domains covered in a systematic review of the literature related to screening for speech and language delay carried out for the NHS in the UK. The structure and process of the full literature review is introduced and criteria for inclusion in the two domains are specified. The resulting data set gave 16 prevalence estimates generated from 21 publications and 12 natural history studies generated from 18 publications. Results are summarized for six subdivisions of primary speech and language delays: (1) speech and/or language, (2) language only, (3) speech only, (4) expression with comprehension, (5) expression only and (6) comprehension only. Combination of the data suggests that both concurrent and predictive case definition can be problematic. Prediction improves if language is taken independently of speech and if expressive and receptive language are taken together. The results are discussed in terms of the need to develop a model of prevalence based on risk of subsequent difficulties.