Does a cluster always equal a cluster? Geographical variation of cluster populations.

Aims and method To provide information regarding the extent to which the process of clustering using the mental health clustering tool captures the complexity of patient need across different geographical areas. Investigation was undertaken via a ‘deep dive’ into patient notes, with data collected on patients allocated to cluster 5, 8 or 13 in three different London boroughs. Results There is evidence for within-cluster differences between patients in different London boroughs in terms of various complexity factors. Further findings in relation to accuracy of clustering suggest some area-specific patterns in terms of clustering practice, raising the possibility that clinicians have different scoring thresholds in different areas. Clinical implications Complexity factors can affect resource use and therefore cost of service provision. In the case of a national tariff, providers of care to more complex patients may be placed at greater financial risk. It is therefore likely that some form of tariff adjustments will need to be introduced so as not to disadvantage patients and clinicians practising in areas of greater complexity.