Clinician holds patients hand

Study of more than 120 English NHS non-specialist Trusts found threshold bias in clinical decision making for patients with one third of Trusts ‘dramatically’ falling away from target.

Published in the BMJ Quality and Safety, researchers from the University of Birmingham and the NIHR Applied Research Collaboration West Midlands have analysed data from non-specialist NHS Trusts in England to look at how clinical decision-making and patient care was affected by a target of 92% of patients being treated within 18-weeks of referral.

Prior to 2020 and the global COVID-19 pandemic, 64% of the 128 Trusts whose data was considered in the study had not met the threshold target of 92% of patients. Following the pandemic, only three Trusts[1] have been able to maintain or return to consistently hitting the 92% patient target, and two trusts[2] have managed to return their percentage of treated patients within 1% of the target for at least one month since March 2020.

The team also observed a ‘threshold bias’, where NHS Trusts may be adapting their decisions on who to treat based on trying to meet the 92% target.

Laura Quinn, a medical statistician at the University of Birmingham and Research Fellow in the NIHR Applied Research Collaboration (ARC) West Midlands is first author of the paper. 

Using publicly available data from NHS Trusts, we have been able to analyse the number of Trusts that have been affected by a ‘threshold bias’ where clinical decision-making behaviour has been affected by how likely the trust is to hit their target of 92% patients treated within the 18-week window. For many trusts, we can see that there is an influx of patients that are treated just ahead of the 18-week threshold, while there is a significant drop in the weeks immediately afterwards.

Laura Quinn, Institute of Applied Health Research, University of Birmingham

“We can also see examples of where some treatment groups are likely to be affected by this threshold bias. This means that in some cases patients aren’t necessarily being treated by clinical need, but because they may be able to be treated quickly to maintain the 92% target. Such targets have created a threshold effect, and so public health policy must take note of this effect and find new levers to ensure that as many patients as possible can get care as soon as possible.”

Analysis of NHS Trusts’ performance on referral to treatment targets also found that there was a steady increase in the numbers of patients having to wait beyond the target 18-week threshold leading up to the Covid pandemic. Between 2015/16 and 2019/20, the percentage of patients waiting beyond that threshold nearly doubled from 8% to 15%.

The team note that the Government decision to drop financial penalties for missing the target has had little impact on Trusts being able to meet that threshold.

The study clearly shows that current targets for referral to treatment are unhelpful and are leading to unintended consequences for patient care; and need to seriously be reconsidered to ensure that care is fair and equitable.

Richard Lilford, Professor of Public Health at the University of Birmingham and Director of National Institute for Health Research (NIHR) Applied Research Centre West Midlands .

“As the NHS has experienced unprecedented pressure over the past 10 years, policies need to change to reflect a growing, ageing population that places increasing demands on healthcare providers. Without a more nuanced set of targets and thresholds for NHS Trusts to work towards, we are likely to see few providers able to meet the threshold and have little incentive to do so when the only back-up target is 12 months.”