The Society of British Neurological Surgeons

Neurosurgical National Audit Programme

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Frequenty Asked Questions.

Q1. What is the aim of the Neurosurgical National Audit Programme (NNAP)?

Q2. Why is this data being published?

Q3. What is HES data and how has it been collected?

Q4. What procedures are included and why?

Q5. What is the difference between elective and non-elective surgery?

Q6. Do all neurosurgeons perform all procedures?

Q7. What is risk adjustment?

Q8. What action is taken if a surgeon has a high mortality rate?

Q9. What does the consultant activity pie chart represent?

Q10. What the consultant funnel plot show?

Q11. What does the Unit activity pie chart show?

Q12. What does the Unit funnel plot show?

Q1. What is the aim of the Neurosurgical National Audit Programme (NNAP)?

The Society of British Neurological Surgeons (SBNS) has established the NNAP to promote improvements in the quality of neurosurgical services and patient care by providing neurosurgical units in the UK and Ireland with a comprehensive audit programme that reflects the full range of elective and emergency neurosurgical activity.


Q2. Why is this data being published?

There is evidence from other national audits that the publication of activity and audit data, when carefully analysed and interpreted, leads to improvements in patient outcomes. The SBNS supports the publication of outcome data that will promote the understanding of the range and complexity of neurosurgical services and the steps being taken to improve those services.


Q3. What is HES data and how has it been collected?

The unit and surgeon level outcome data presented in these reports is based on the analysis of Hospital Episode Statistics (HES) data linked to records of patient deaths kept by the Office of National Statistics (ONS). Hospitals record information on every patient admission using codes for diseases and conditions (ICD10) and codes that reflect operations and procedures (OPCS4). The HES data is submitted to a data warehouse that is managed by the Health and Social Care Information Centre (HSCIC).

Each HES record contains a wide range of information including:

The Neurosurgical National Audit Programme has used this detailed dataset to present activity and mortality data for all neurosurgical units and all consultant neurosurgeons practising in the NHS in England.


Q4. What procedures are included and why?

The outcomes presented are based on all elective (planned) operations undertaken by consultant neurosurgeons in England. This is the first national audit to report on all the activity of a surgeon, rather than selected index procedures.


Q5. What is the difference between elective and non-elective surgery?

An elective surgical procedure is usually a planned procedure that has been booked in advance and has involved outpatient consultations and investigations. A non-elective surgical procedure usually follows an emergency or urgent admission to hospital often through an emergency department or by direct transfer from a district general hospital to the neurosurgical unit.


Q6. Do all neurosurgeons perform all procedures?

All neurosurgeons perform a core set of emergency neurosurgical procedures. Most neurosurgeons will also specialise in one or several subspecialist areas such as: spinal, neurovascular, functional and skull base surgery. Paediatric neurosurgeons specialise in neurosurgical operations on children.


Q7. What is risk adjustment?

The NNAP presents risk adjusted (or case-mix adjusted) mortality data to take account of the fact that neurosurgeons undertake a wide range of operations of varying duration, complexity and risk and that some patients may be at higher risk because of their age or underlying problems with their health. Risk adjustment allows a fairer comparison between individual surgeons; but it is important to remember that risk-adjustment does not account for all factors influencing a patient’s outcome. It should also be noted that modern neurosurgery is a complex process that involves teams of neuro-anaesthetists, interventional radiologists, other specialist surgeons and intensive care specialists all of whom contribute to the final outcome of the patient.


Q8. What action is taken if a surgeon has a high mortality rate?

All national audits have in place arrangements for reviewing the outcomes of surgeons and units that appear to be outside the expected range. The range is defined using standard statistical methods. The SBNS-NNAP Outlier Policy defines this process in greater detail. The mortality outcomes of all consultant neurosurgeons practising in NHS England in the audit year were within the expected range.


Q9. What does the consultant activity pie chart represent?

This pie chart shows the number of elective procedures (procedures that were undertaken as part of a planned admission to hospital) undertaken by the above named consultant during the audit period 1st April 2014 to 31st March 2017. Elective procedures that were undertaken as day cases are not included in these figures. Furthermore, if a patient underwent more than one elective procedure within the same admission to hospital, only the main procedure has been counted and included in the figures above.

This pie chart does not include the non-elective (emergency) procedures that were undertaken by this consultant during the same audit period. Non-elective admissions make up approximately 50% of a consultant neurosurgeon’s activity.

The pie chart splits elective procedures into spinal, cranial, and other. Spinal procedures include operations performed on the discs and bones of the spine. Cranial procedures include all operations that were performed on the brain and surrounding structures of the head. Other procedures include some elective diagnostic procedures, peripheral nerve surgery and specialist procedures such as radiosurgery.


Q10. What the consultant funnel plot show?

The consultant funnel plot displays the risk adjusted mortality rate for the named consultant. The dot that is displayed on the graph represents the individual surgeon and is aligned with the expected number of deaths on the x-axis (horizontal axis) and the risk-adjusted mortality rate on the y-axis (vertical axis). The yellow line represents the national average elective procedural mortality rate. The sloping solid black line represents a control limit. A control limit is, in effect, a performance boundary. Any consultant who falls within this boundary is practicing to the expected standard.


Q11. What does the Unit activity pie chart show?

The Unit activity pie charts represent the total number of elective (planned) admissions and non-elective (emergency) admissions. An admission represents a single patient’s care from admission to discharge. The unit level pie charts are segmented to represent the proportion of patients undergoing cranial, spinal, other procedures and patients undergoing no procedure.


Q12. What does the Unit funnel plot show?

The Unit funnel plot shows the risk adjusted mortality rates of 30 neurosurgical units in England. Each dot represents a neurosurgical unit. The dot is aligned with the expected number of deaths for the unit along the x-axis (horizontal axis) and the risk adjusted mortality rate along the y-axis (vertical axis). The two solid black lines represent control limits. These are effectively ‘performance boundaries’. Any unit performing within the control limits is performing to the expected standard.