Fair, unbiased analysis of surgical outcomes

It is imperative – for patients and surgeons alike – that measures of quality are properly adjusted for the individual
conditions of the patients receiving treatment and the complexity of the care involved.

CRAB Surgery is the result of thirty years of research and development, and automates the POSSUM audit methodology,
published by Copeland at al in 1991 and in use around the world.

POSSUM methodology is recommended by the Royal College of Surgeons and the National Confidential Enquiry
into Perioperative Deaths (NCEPOD), among others.

CRAB is unique in calculating the risk for every patient as an individual rather than making assumptions about patients from national statistics.


CRAB provides a fair, representative system for monitoring and demonstrating the quality of patient care.

It enables quality measurement via a web-based system that uses the hospital’s own coding data.

Case-mix adjustment

Calculate the risk profile for every patient as an individual using 18 clinical variables.

Root cause analysis

Produce immediate root cause analysis data without the need to review patients' notes.

Automated data capture

Capture data for practice audit, research and peer review, appraisals and revalidation.

Improved coding

Better analysis and benchmarking enables clinicians to review coding.

More informed mortality
and morbidity reviews

Objective analysis of risks and outcomes informs mortality and morbidity reviews.


Compare quality against the largest dataset of its kind in the world.

An innovative solution

Statistical tools and general proxy measures, such as death and readmission rates, have been the long-standing quality metrics in the absence of anything more sophisticated.

These may work at a national or regional level for general planning, but neither necessarily gives a true picture of local clinical quality. Insufficient account is taken of the types of patients clinicians have to treat.

CRAB has been developed in partnership with Mr. Graham Copeland, the architect of the POSSUM surgical audit system. It is a world-renowned methodology for risk adjustment and assessing clinical performance against case-mix.

Assessments of clinical quality and performance can be reached with a reliable evidence base, and the raw data may be reviewed by drilling down to individual cases in the risk report.

CRAB is a peerless benchmarking application, referencing a growing dataset of clinical variables drawn from more than 14 million anonymised records. This dataset has been built up over nearly 25 years and there are now over 300 hospitals worldwide contributing to it -70 per cent of this data is UK-based, ensuring benchmarking of NHS practice is relevant and accurate.

CRAB has been designed to interface with existing Hospital systems so that data may be collected automatically.

Quality improvement

NHS Litigation Authority

CRAB software has enabled the Trust to progress its application for Level 2 NHSLA status and it is confident that the software will assist progression towards Level 3.The Trust would be able to generate a saving of circa £200,000 by meeting Level 2 with a further £200,000 should Level 3 be achieved.


Activity has been coded to a greater depth as a result of using CRAB in the Trust’s clinical benchmarking group. The group looks at monthly reports and any alerts CRAB raises which require additional assessment.

This has encouraged dialogue between clinicians and clinical coders on how respective episodes of care should be coded. As a result the Trust’s coding has increased accuracy which in turn has had a positive effect on the funding the Trust receives.


The mortality rates and complications rates of the Trust continue to improve and the introduction and use of CRAB has made a positive contribution towards this.

Foundation trust application

In our foundation trust application we highlighted CRAB as an example of proactive risk management and how subsequently we developed a clinical benchmarking group to use the software to manage clinical variance.

Monitor was very impressed with this approach and we were able to state that CRAB allowed the Trust to make more timely interventions when required. Furthermore, the tighter confidence intervals that resulted from using CRAB meant that a great deal more clinical alerts were highlighted than would have been when using, for example, Dr Foster.

At the 'board to board' meeting the medical director highlighted our use of CRAB for clinical risk management, and we received positive comments regarding how proactive we had been in this area.

Commissioning for quality and innovation

The Trust was able to secure circa £96,000 revenue in 2009/10 from the PCT for the development of the CRAB software suite - 0.1% of the contract value.

To read more Case studies click here.


Professor Lord Darzi“CRAB can identify outcomes that are better than expected, as well as those that are worse, and thus can be used as an improvement tool as well as to assure clinicians and others of the standard of care being provided, and to measure productivity.”
Professor Lord Darzi
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