The Threshold Common Language tool is designed to provide a structure for making decisions about impairment. It encourages practitioners to collect data about a child’s health and development and to analyse it in a logical sequence in order to arrive at a rounded judgement.
The information is used combination with other criteria when making decisions about when and how to intervene in a child’s life. For example, other factors to bear in mind include legal and moral imperatives, pragmatic considerations and the views of consumers.
Impairment is considered on various developmental dimensions, including physical, educational and emotional components. Decisions about the significance of the impairment emerge from applying five tests, for instance comparing extremes to the norm, or estimating persistence across several developmental stages.
The tool uses a record sheet and decision tree to help practitioners make these judgements. It encourages them to draw on research, to record their working-out and to discuss their findings with colleagues.
Threshold can be applied at the clinical level when undertaking an assessment. Comparisons between people making judgements on the same cases indicate that it has a high degree of inter-rater reliability, and the results can be compared with other impairment measures in order to test for validity. The tool can also be used as a training tool or in supervision.
The results from applying Threshold can be aggregated to give a sense of the seriousness of needs being dealt with by an agency. Such information can be useful when planning services, for example to identify children who are currently receiving help who do not need it, as well as those who need more than they are getting.