Four years after the first wave of independent sector treatment centres, the Department of Health has provided data on their performance. Unfortunately, this is almost useless in answering questions about their impact on waiting times.

Published as a single table last month, with a promise that this will be available annually, the DoH details contract values, total procedures contracted, usage rates (as a percentage of contract value) and a breakdown of procedures by specialty for 25 of the 27 first wave ISTCs.

The charts in the attached PDF (see resources box, bottom right) are almost the sum total of the sort of analysis that can be derived from the the DoH. Even these required estimates and apportionments to be made.

A key bit of missing data is usage in terms of the number of procedures carried out. The data only shows usage as a proportion of contract value. These percentages have been used to estimate procedures carried out, and these have in turn been apportioned across financial years based on the start-up date for each centre and an assumption that work was evenly distributed.

What this reveals is the relatively small scale of work each year carried out compared with the NHS as a whole.

Although some ISTCs carry out diagnostic work as well as elective inpatient/day case procedures, there is no separate analysis of the use of these services. And nor is there any disaggregation of the contract value according to specialty. A handful of centres specialise in orthopaedic procedures so it is possible to compare unit costs of procedures by centre. This shows a variation of up to two-thirds in costs, but without more detailed case-mix data it is impossible to say much about these figures.

A claimed benefit for ISTCs is they have helped cut waiting times but there is no real data to support this. Apart from not knowing how many patients were treated, we do not know how long patients waited. This matters because it is impossible to carry out proper analysis of the ISTC programme. It is also virtually impossible for the Healthcare Commission to analyse and report on performance based on routine statistics, or for patients to make choices based on performance information, or for primary care trusts to assess the worth of contracting with ISTCs.

We may not know all there could have been to know about the half million people so far treated by ISTCs, but as choice of any hospital looms, it will be increasingly vital that all providers treating NHS patients comply with all the information requirements of an NHS hospital.