Assessment and investigation of the child with disordered development.

Every paediatrician, generalist or specialist, at every level and in every setting will come across the child or young person with disordered development and has a duty of care to ensure that appropriate assessment and investigations are undertaken, if each individual is to be given the best possible opportunities to achieve the highest possible level of participation and enjoy the best possible quality of life. Using a structured approach, all paediatricians have the potential to make a significant positive difference and should seek every opportunity to do so, even if seeing the child for an entirely different reason. Key messages of this article include: (1) each child is unique and requires careful, individual, clinical assessment and thought before any investigations are undertaken; (2) there is no single list of appropriate tests to be done for all children with disordered development; (3) the clinical judgement of the experienced clinician (expert triage) is more helpful than 'guidelines' in deciding which investigations to do; (4) clinical networking with colleagues in paediatric neurodisability, neurology, clinical genetics, metabolic paediatrics, and so on, is essential to achieve the highest possible yield from investigations and to reduce the number, discomfort and expense of inappropriate investigations; (5) the more effort and thought that goes into formulating differential diagnoses, the more appropriate the investigations are likely to be and the higher the likely diagnostic hit rate. Diagnostic hit rates up to 80% have been reported in the literature for those with severe learning disabilities and this is likely to be even higher once microarray comparative genomic hybridisation becomes more widely available.