Why is the planned care waiting list coming down and what does the data really tell us?

Governments have been trying to reduce waiting times for planned consultant-led hospital care, sometimes called referral to treatment (RTT) waiting times, for decades. The NHS’s target is to see 92% of patients referred by GPs for non-urgent planned hospital treatments – including operations, appointments and procedures – within 18 weeks. Waiting times reached record lows in 2010, but the 92% target has not been met since 2016. During the Covid-19 pandemic, the waiting list increased even more steeply than it had done in the previous decade, prompting funding to support elective recovery and an elective recovery plan aiming to increase planned care activity and reduce waiting times.

The Labour government published their new elective reform plan in January this year, committing to reduce long waits by empowering patients to choose when and where they have their treatment, delivering more planned care, moving provision out of hospital and into community settings, and rewarding performance – notably financially incentivising improvements, and paying the NHS for data validation. ¹

When Wes Streeting celebrated the improvement in the waiting list – saying “thanks to our interventions and the hard work of NHS staff, the overall waiting list has now fallen in April for the first time in 17 years” – the most straightforward assumption was that the NHS is delivering more operations and appointments that reduce the overall list of people waiting. But is this really the case?

What is the trend in the waiting list?

The waiting list is made up of incomplete patient pathways, measuring the time from referral to a specialist to the start of treatment. ²  In the years before the pandemic, the waiting list for elective care was increasing (Figure 1). From September 2023 until May this year, the waiting list has plateaued and decreased.

How many people are moving on and off the waiting list?

The size of the waiting list is affected by patient pathways joining and leaving it. A pathway is the route of a patient through the health system, which starts with a referral, and there are more pathways on the waiting list than individual people. In the reported data, the number of new referrals is consistently greater than the number of pathways reported as complete (meaning the patient has started treatment or their treatment needs have changed). In other words, more patients are being referred for treatment than leaving the waiting list.

In May this year, the ratio of completed pathways to new referrals was 0.86:1, meaning that per every 100 referrals for planned care, only 86 patient pathways were completed (Figure 2).

There appears to be a contradiction in the data. Even though the ratio of completed pathways to new referrals has been consistently below 1:1, which we would expect to cause the waiting list to increase, we know that the waiting list has levelled off and started to reduce.

Over this time, the gap between people being referred and starting treatment (Figure 2) has decreased slightly, and the ratio has improved. The NHS has rightly celebrated an upward trend in the number of planned treatments provided, but demand is still increasing too. While the narrowing of the gap between demand and supply has contributed to waiting lists flattening, activity has not increased to meet or exceed the number of new referrals, and so alone would not be sufficient to cause the reduction in the waiting list.

What else is affecting the size of the waiting list?

A less visible factor is also affecting the size of the waiting list, not shown in data on new referrals and completed pathways.

In any given month, we expect the size of the waiting list to equal the incomplete pathways from the month before, plus new referrals in the given month, minus the reported completed pathways in the given month. But when we compared our calculated expected waiting list figures to the reported waiting list in the publicly available data, the size of the reported waiting list has been consistently smaller than the expected waiting list.

This shortfall between the expected and reported waiting list represents pathways that are not reported as completed pathways, but removed from the list anyway, and can be described as “unreported removals”. Over the two previous complete financial years (from April 2023 to March this year), there have been on average 244,578 unreported removals a month (unadjusted for working days), and 7,566,344 incomplete pathways (making up the reported waiting list) a month. This means that, on average, unreported removals equate to around 3% of the size of the waiting list. For context, the waiting list dropped by 29,814 between April and May this year, or by 0.4%.

What could unreported removals represent?

The three key factors likely to be driving unreported removals are:

• Validation: validation has been part of plans to address the waiting list for planned care for several years. There has been a policy push this year that resulted in a validation “sprint” in April (a time-limited initiative to remove pathways from the waiting list which should not be there), notably after an uptick in unreported removals that started in September 2023 (Figure 3). Some of the unreported removals are likely to represent pathways that were completed but not recorded as such at the time. These pathways are removed from the waiting list during validation and may never appear as reported completed pathways if the historical completed totals, already submitted, are not revised. It is impossible to determine using publicly available data what proportion of unreported removals reflect unreported completed pathways. Other consequences of validation, like deletion of errors or duplicate referrals, are also difficult to quantify.
• The design of the reporting process: if a patient does not attend a first appointment after a referral, this effectively strikes the outstanding referral from the record. If the referral has already been reported as an incomplete pathway by the time the patient does not attend, it may later become an unreported removal without a corresponding completed pathway.
• Software and data management processes: some referrals made via the NHS e-Referral System are not immediately booked into appointments and join a list called “Appointment Slot Issues”. The problem with this system is that referrals are automatically removed from the list after 180 days without an action. Referrals waiting on Appointment Slot Issues lists are required to be reported in routine RTT data submissions, but this does not always happen. As a result, it is unclear to what extent any referrals which disappear from local Appointment Slot Issues lists after 180 days contribute to unreported removals, or whether instead they may never be recorded in RTT data and therefore represent an unquantified, and potentially lost, additional waiting list. ³

How do unreported removals affect the waiting list?

While the waiting list has started to go down, unreported removals have gone up (Figure 3). In fact, they have repeatedly outnumbered the additional incomplete referrals that join the waiting list every month. This tells us that, across several months, there were more pathways being removed from the waiting list without being marked as complete than pathways joining the list.

What is the impact of unreported removals in combination with the ratio?

Over time, the balance between new referrals and completed patient pathways affects the size of the waiting list. If more people are referred than treated, the list grows. Changes in this balance can speed up or slow down that growth.

Removals of still incomplete pathways from the list, which go unreported, reduce the total size of the waiting list. During periods when new patients waiting for treatment far outnumbered these removals, their effect was more hidden. But as the list grew more slowly, they began to have a more noticeable impact. Since September 2023, this shift has helped the NHS get control of the waiting list, even while according to its own data it is still treating fewer patients than are being referred.

What are the implications of the complexity of waiting list data?

The overall size of the waiting list is a critical indicator of the backlog of patients needing care. Our analysis has shown that it is less useful for understanding how need is being met. This is particularly apparent when the trend of the waiting list changes, and we try to understand why and what the changes mean.

Commentators have recently expressed concern about the kind of validation that the government’s promised incentive payments might encourage. Improving the data quality of waiting lists is important to ensure that people who should not be on the list, like people who have been treated privately or left the country, are no longer counted among those waiting to be seen. However, accusations of gaming the validation process, by removing referrals from the waiting list inappropriately without treatment, are likely to persist in the absence of transparency about what actions the unreported removals materially represent.

The NHS is delivering more planned care, but still not enough to keep up with demand. The planned care that is reported is not enough to explain the reduction in the elective waiting list, and the publicly available data provides little more insight. Wider context like the push for validation sheds some light on the shape of the waiting list. Analysis of the Further Faster 20 programme – a scheme intended to reduce waiting lists using teams of “crack clinicians” – also found that reductions had more to do with reduced referrals and unreported removals than increased activity. Wes Streeting has praised “record investment and fundamental NHS reform” as the reasons behind reducing the waiting list; the success of the validation sprint goes unmentioned. 

The information available in the public domain is insufficient for independent scrutiny of the elective waiting list, and consequently for holding government to account. Removals from the waiting list should be described in publicly available data in a meaningful way; the current process is unduly obscure. Until more transparent reporting is provided, accountability around unreported removals remains impossible and the planned care waiting list will continue to be a misleading indicator of how the NHS is dealing with demand. Furthermore, if the government is to make meaningful progress on reducing waiting lists, it must find a way to deliver more care to the millions of patients still waiting.