Chief statistician’s update: explaining NHS activity and performance statistics

Revised on 21 July 2022 to include information on new data.

Darllenwch y dudalen hon yn Gymraeg


This blog post was originally published in March 2022 to explain how we measure NHS activity and performance. The post has been updated today to include new developments on measuring the number of patients waiting for treatment. Every month we publish the latest statistics on NHS activity and performance. Interest in these statistics has increased in recent years, given the wide-ranging impact of the pandemic. This blog aims to provide more context to its key concepts so that our statistics are widely understood and used appropriately.

The statistical release summarises activity levels of NHS services in the latest available month. It also reports against performance targets set by the Welsh Government.

Digital Health and Care Wales and the Welsh Ambulance Service Trust supply data for this release.

What the data measures 

The data captured typically counts the number of times an NHS service is used. It is a common misconception that this is a count of the number of patients who used the service.

In practice this means that we report on the number of:

  • calls made to the ambulance service, not the number of people who called the ambulance service
  • attendances at emergency departments, not the number of people who attended emergency departments
  • referrals for first outpatient appointments, not the number of people referred
  • patient pathways waiting for diagnostic tests or therapies, not the number of people waiting
  • patient pathways waiting to start treatment; not the number of people waiting

Why the use of these terms matter

While it may seem that terms like ‘patient pathways’ and ‘patients’ are interchangeable, the key difference is that the same patient might use NHS services many times. A single patient is only counted once in a patient measure but may be counted many times in a patient pathway measure. Similar principles apply to ambulance calls, emergency department attendances and referrals.

This means that the number of patients waiting for NHS services is always lower than the number of patient pathways that are open. Using measures like patient pathways therefore allows us to measure the full scale of NHS activity in a way that counting “patients” only wouldn’t.

Up to very recently, the NHS data we have access to in the Welsh Government has been at a pathway level only so it hasn’t been possible to measure activity based on patients. However, new management information suggests that in March 2022, when there were over 701,000 open patient pathways, there were around 544,000 individual patients on treatment waiting lists in Wales. This is based on a new method and there is some uncertainty around the estimate, so we’re working to better understand the strengths and limitations of this data and the potential for further analyses. In the meantime, given the interest in understanding numbers of patients on waiting lists, we think this provides useful and important context in support of the headline figures on patient pathways.

For cancer services, where the new process for collecting suspected cancer pathway (SCP) data allows for patient-level analyses, the picture is quite different. It shows that the number of patient pathways opened in a month is only 2% to 3% higher than the number of patients who had pathways opened. Still, as the purpose of this release is primarily to measure the activity and performance of NHS services in a given month, ‘patient pathways’ is the most appropriate measure to use.

How patient pathways work

A patient pathway opens when the hospital receives a referral. The patient’s waiting time starts at this point. Referrals are most commonly submitted by GPs but may also come from other health care professionals. Patients with complex needs may have referrals for multiple types of treatments so may have many pathways opened. The main activity measure for referral to treatment time is a count of the number of patient pathways which are open at the end of each month. This can be thought of as ‘the waiting list’. 

Performance against the two referral to treatment performance targets are measured by calculating:

  • the percentage of pathways where the wait was less than 26 weeks
  • the number of waits that were longer than 36 weeks in a given month

If a patient has more than one referral they will appear in the dataset more than one time. This means that the same patient can have different pathways counted in the calculations for both targets.

A patient pathway is then closed if either the patient starts treatment, or if following consultation with a hospital specialist, no hospital treatment is necessary. This could include:

  • patient admitted to hospital for an operation or treatment
  • starting treatment that does not need a stay in hospital (for example, medication or physiotherapy)
  • beginning the fitting of a medical device such as leg braces
  • starting an agreed period of time to monitor the patient’s condition to assess the need for further treatment

Closed pathway data included in the statistical release can be thought of as a measure of ‘referrals completed’. This is where patients have received the service they were referred for.

In other words:

  • open pathways count the waiting lists for all treatments
  • closed pathways count the number of pathways taken off the waiting list

If the waiting list is to reduce, the number of closed pathways in a month must exceed the number of new pathways added to the waiting list in the same month.

How does this compare with other UK countries

All four UK countries publish information on a range of NHS performance and activity statistics. These statistics are not exactly comparable between nations. Methods of data collection vary across the UK as they track performance targets that have developed for each country. However, each nation measures the concept of patient pathways rather than patients.

Statisticians in all four home nations have collaborated as part of the ‘UK Comparative Waiting Times Group’. The group looks across published health statistics, in particular waiting times, and compile a comparison of:

  • what is measured in each country
  • how the statistics are similar
  • where they have key differences

This information is available via the Government Statistical Service website and is an area of work we intend to restart shortly.

Further information

Quality reports provide further information on each subject area within the statistical release. 

Ambulance services: quality report

Time spent in emergency departments: quality report

Outpatient referrals: quality report

Diagnostic and Therapy waiting times: quality report

Referral to treatment: quality report

Stephanie Howarth
Chief Statistician