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Our definitions, remit and deliverables

Find out more about the National Casemix Office (NCO), its context within the health service, casemix methodology and the development and design of HRGs.

Our definitions, remit and deliverables

The term casemix has a number of meanings, from the literal mix of cases (patients) seen by a consultant, hospital or region, to the way patient care and treatments are classified into groups. These groups provide a useful measure on which to make performance comparisons, to cost healthcare, or to fund it.
The NCO are commissioned to develop and maintain a set of casemix groupings, called Healthcare Resource Groups (HRG), which provide a clinically-endorsed view of acute healthcare activities undertaken within the English NHS. These groups are generated via the Casemix Grouper Software, and the most current iteration is known as HRG4+.

HRGs are designed by clinicians to represent clinical care, within the boundaries of available, nationally mandated, data. Clinical leads on Casemix Expert Working Groups (EWGs) are nominated representatives of the Royal Colleges and professional bodies within the UK, and are joined on EWGs by finance and informatics professionals to ensure the HRGs can be practically implemented within the current national structure. They not only represent specialist hospitals, but also providers undertaking less complex, more routine, care. EWG members are not reimbursed for the time or expertise they provide.

Given that the HRG structure is currently aligned with patient body-systems, for both surgical and medical activities, there are over 30 EWGs that input into the development of the HRG Casemix Classification. Future enhancements for the development of Community Health Groups will expand this number.

Clinical input and experience has allowed the current HRG4+ classification to acknowledge the additional resource use required when treating patients who:

  • have multiple complications and comorbidities that affect the clinical input for their care
  • require surgery at a very young age
  • require multiple procedures to be undertaken at the same time, within the same hospital admission or attendance
  • require surgery that utilises new devices, or innovation in traditional clinical approach
  • require more complex, rather than routine, care

For more information,  icon download our science of casemix guide. [689.45KB]

Design framework

The icon design framework [924.07KB] outlines the key principles that are essential to any casemix classification, and draw heavily from those utilised in the development of previous casemix classifications. The fundamentals are intended to assist EWG members in the assessment and interpretation of data and lay down the preferred strategic foundation and aims for the classification. 

Stakeholder engagement

Engaging with over 250 healthcare professionals across 33 EWGs covering all clinical areas drives the design of HRGs and provides valuable input into the development of the HRG4+ Grouper software products. Download the icon NCO EWG membership list [262.27KB] .

Our icon stakeholder engagement process flow diagram [148.9KB] highlights how potential oddities, or areas of improvement, relating to casemix products can be raised. It also demonstrates other routes that can lead to change in casemix products.

If you have a question about our Grouper products, please call 0300 303 5678 or email

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