The NHS is getting better value for money from privately-run treatment centres as they become more popular with GPs and patients, according to Laing & Buisson.
However, the results mean that millions of pounds are still being spent on treatments that do not take place.
Figures obtained by the market analyst's Healthcare Market News reveal that use of independent sector treatment centres (ISTCs) has risen since the last time comprehensive contractual information was published in 2008.
Combined, all 23 existing schemes performed an average 97% of their contracted value between October and December last year, 10% up from two years ago.
The controversial ISTC programme was launched by the Blair government in an attempt to outsource routine surgeries from NHS and cut waiting lists.
But the inclusion of volume guarantees meant primary care trusts were charged for a specified number of procedures regardless of whether or not they were carried out.
The coalition government is set to continue the programme and its Health and Social Care Bill will increase the premium above NHS rates given to ISTCs for each operation to 14% from the present 11%.
The research found that at the end of 2010, Circle-run Burton ISTC and UK Specialist Hospitals Somerset ISTC, both of which expire in July, were the only wave one schemes that reported take-up rates below 90%.
Care UK's Portsmouth scheme was operating at 90% of its contracted value, but the remaining ten schemes, including three NHS walk-in centres, all recorded utilisation rates in excess of 97%.
These thirteen ISTC contracts are due to expire this year and, the report added, although volume guarantees will not apply to the new agreements, their renewal is likely to be heavily dependent on past contractual performance.
Maria Davies, editor at Healthcare Market News, said: "These figures should bode well for the current round of ISTC contract renewals and in the main providers are reporting increased interest from patients and greater acceptance from GPs and local NHS managers.
"However, there are fears that regardless of how well they are performing, some schemes could take the brunt of the spending squeeze as cash-strapped NHS managers look to cut or downsize private sector contracts rather than scale back in-house services or make reductions in their workforce."
