Tony Jewell and Hilary Spiers in their feature, 'Tales of the expected' (pages 30-31, 2 November), used data from three local acute trusts to highlight peaks and troughs in emergency admissions for respiratory problems.

These important annual trends in demand, with their corresponding resource implications, correspond with nationally based research carried out recently by the NHS Information Authority's population health and service management information programme.

The work was made possible through links with Chris Aisbett, a statistician with particular interest in case-mix issues in Australia. Clusters of healthcare resource groups (HRGs) with similar admission patterns are identified according to a statistical algorithm.

This method highlights a cluster of 21 HRGs (mostly, but not all respiratory HRGs), which graphically demonstrate increases in demand and winter pressure periods.

When considered at individual provider level, there is the opportunity to understand the types of admissions associated with these peak times locally.

Population health and service management information programmes can provide trusts with their own patterns of emergency respiratory admissions so defined, together with peer group comparisons.

Ian Hart Data analyst PH&SMI NHS Information Authority