A shocking study has suggested that hospital trusts in England are choosing which patients to treat based on certain targets rather than clinical needs, claims the NHS has denied.

Those behind the study warned the 18-week referral to treatment standard gives hospitals “no encouragement” to treat those who have only been waiting a short time, or who have passed the threshold.

The target – set at 92% – was introduced in 2012 to ensure patients are waiting no longer than 18 weeks from GP referral to starting treatment for routine, non-urgent conditions.

However, a team spanning the University of Birmingham, the University Hospitals Birmingham NHS Foundation Trust and the West Midlands Academic Health Science Network said it can have “unintended consequences”.

Researchers referred to this as the “threshold effect”, which shows up as a spike in the data, known as discontinuity, and appears around the target threshold.

They analysed monthly waiting times data for all 144 non-specialist acute NHS hospital trusts in England between January 2016 and September 2021.

The team said the figures “repeatedly showed a large spike in the number of trusts exactly meeting the 92% target threshold for the 18-week standard, followed by a sharp drop after the target had been reached”, suggesting some trusts were treating the minimum number of patients waiting under 18 weeks in order to comply with the standard.

They added that “the target provides no encouragement to treat patients who have only been waiting for a short time or who have already passed the 18-week wait”.

“Policymakers should be circumspect in their use of targets. Second, if targets are used, then policymakers should examine for threshold effects routinely. Third, targets should be carefully designed to mitigate threshold effects.”

A richer picture of how the system being measured works and how its staff and managers behave and are motivated is needed for sustainable long-term change

The percentage of trusts where patients waited less than 18 weeks also fell after the removal of a financial sanction for missing the targets was removed in 2016/17.

Nigel Edwards, chief executive of the Nuffield Trust, also said the study – published in the journal BMJ Quality & Safety – “joins a long litany of examples of the unintended impact of targets”.

He added: “The most sustainable approach to meeting a target is to redesign processes and realign resources to ensure that the targets are met as a by-product of a well-designed system.

"Unsustainable level of work from staff"

“However, if there are insufficient resources – for example, in the case of waiting lists where demand exceeds capacity, or the organisation lacks the skills and resources to undertake a major review of processes and ways of working – less desirable approaches may be taken.”

Mr Edwards said these could include requesting an “unsustainable” level of work from staff.

He added: “The experience of the use of targets in the English NHS, as evidenced by (the study authors) and many other researchers, suggests that over-reliance on a small number of high-profile measures is risky.

“A richer picture of how the system being measured works and how its staff and managers behave and are motivated is needed for sustainable long-term change.

“Effective performance improvement systems cannot be built solely on targets but need a great deal of managerial judgement.

“The improvement system and the local teams delivering improvement both need the management capacity to make good judgements to avoid the issues of gaming, overpromising, and other perverse ways of pursuing the metric while missing the point.”

An NHS spokesperson told PA: “The suggestion that the NHS is incentivising trusts not to bother treating people once they pass 18 weeks is nonsense – treatment priority is determined by the clinical needs of patients as identified by clinicians as well as those waiting longest.

“The NHS has a clear plan in place for reducing the Covid backlog, which has inevitably built up as a result of the pandemic, with significant progress reducing the longest waits.”

The concept of referral-to-treatment was first introduced to the NHS in 2004 – under the Labour government – with the 92% target introduced 12 years later.

The Labour Party and the Department of Health and Social Care have been approached for comment.