Last update 20th. February 2005


Request for Information from the NPSA

February 16 2005

By Email

Dear Nick

4-8 Maple Street

London W1T 5HD

Tel: 020 7927 9500

Fax: 020 7927 9501

Subject: Request for Information from the NPSA

Thank you for your email of 26th January 2005, requesting information on patient safety in the NHS. I hope the following information answers your questions as fully as possible.

First, some background on the work of the National Patient Safety Agency, and how we collect data on Patient Safety Incidents.

National Patient Safety Agency (NPSA) and the National Reporting & Learning System (NRLS)

The NPSA is a Special Health Authority working across England and Wales towards a safer NHS for patients. One of our statutory functions is to set up a National Reporting & Learning System, collect reports of patient safety incidents and to learn from them, including developing solutions to enhance safety.

The NRLS was developed to promote comprehensive national learning about patient safety incidents. The NRLS receives reports about patient safety incidents from NHS organisations, staff and contractor professions. These reports are based on a dataset developed with wide input from NHS organisations and clinicians involved in developing and testing the system. We define a patient safety incident (PSI) as any unintended or unexpected incident which could have or did lead to harm for one or more patients receiving NHS-funded care.

Patient safety incident reports are collected into a specially designed, confidential and anonymous national database. This is based on experience of the value of confidential reporting systems from across the world in both health care and other industries which demonstrate that confidential systems support wider reporting and enhance learning from incidents. The database is still at an early stage of data collection and analysis.

Reports generated from the NRLS are analysed with expert clinical input to help understand the frequency and types of patient safety incidents, patterns and trends and underlying contributory factors. This data is then used for development of solutions, for surveillance and monitoring, and for feedback to enhance learning across the NHS.

Further information on the NPSA, the NRLS and the NRLS dataset can be obtained from our website at

You have asked about the criteria we use to classify an incident as adverse and what degrees of classification are used to define an adverse event. We have defined a patient safety incident above - we do not use the term adverse event which goes beyond the definition of PSIs.

We classify patient safety incidents by type of incident and degree of harm.

Type of incident includes the following categories:

Degree of Harm is categorised as no harm, low moderate, severe and death.

A Low degree of harm is defined as follows:

Any unexpected or unintended incident that required extra observation or minor treatment and caused minimal harm to one or more persons.

Examples may include:

Perforation of the bowel during surgery that was repaired at the time and the area was appropriately washed out. Only antibiotic treatment is required.

A patient is given someone else's medication. The medication is the same as they normally take, but at a slightly higher dose, and they need to go to bed earlier due to drowsiness.

A Moderate degree of harm is defined as follows:

Any unexpected or unintended incident that resulted in further treatment, possible surgical intervention, cancelling of treatment, or transfer to another area, and which caused short-term harm to one or more persons.

Examples may include:

Perforation of the bowel during surgery was not picked up at the time. It results in septicaemia and a return to theatre for repair.

A patient is given someone else's medication. The medication is stronger than their own and they suffer prolonged drowsiness for a week. The patient needs frequent observation of their respiratory rate.

A Severe degree of harm is defined as follows:

Any unexpected or unintended incident that caused permanent or long-term harm to one or more persons.

Examples may include:

Perforation of the bowel during surgery, requiring a temporary colostomy and subsequent major operations.

A patient is given someone else's medication. They have an allergic reaction to it, have a cardiac arrest and suffer brain damage as a result of receiving the medication.

Death is defined as follows:

Any unexpected or unintended event that caused the death of one or more persons.

Examples of patient safety incidents involving Death may include:

Death as a direct consequence of perforation of the bowel during surgery.

A patient is given someone else's medication. They have an allergic reaction to it, have a cardiac arrest and die as a result of receiving the medication.

Further details and examples are available on the NPSA website within the help section available at the following

You have also asked for the number of adverse incidents recorded in the last year and an estimate of the number of unrecorded incidents.

The NPSA will regularly publish aggregate statistics and analysis of incident data to promote a learning culture and the development of patient safety improvements in the NHS. We will be publishing our first major analysis of the NRLS as part of a report from our Patient Safety Observatory in mid-summer 2005 and details will be available on the NPSA website. Hopefully, this publication will provide you with the information you require. However, as patient safety incidents are self-reported they are not necessarily representative of the NHS across England and Wales and therefore need interpreting with care. This also means that we cannot provide any accurate estimates on the number of unrecorded patient safety incidents.

There have been estimates of the level of adverse events in the NHS which can be found in the Department of Health report, An Organisation with a Memory (OWAM), and in our own Seven Steps for Patient Safety. I include relevant extracts from OWAM below on this. This is a challenge to all modern health services in the developed world.

"Currently, NHS reporting and information systems provide us with a patchy and incomplete picture of the scale and nature of the problem of serious failures in health care. We know, for example, that every year:

Just as none of these statistics can be attributed wholly to service failures, research in this country and abroad suggests that they give no indication of the potential true scale of the problem. This issue has been the subject of major pieces of academic research in Australia and the USA, but work in the UK is in its infancy. Yet the best research-based estimates we have reveal enough to suggest that in NHS hospitals alone adverse events in which harm is caused to patients:

OWAM 2000

There is evidence that all reporting systems tend to underestimate the true number of incidents, for a variety of reasons. Whilst definitions vary, the study by Charles Vincent and colleagues using case note review in two London hospitals suggested that as many as 10% of patients may have some form of adverse event, with about 50% being preventable. Our pilot studies of the NRLS gave rates nearer 3% for patient safety incidents. It is for this reason that we have set up a Patient Safety Observatory to bring together information from a variety of sources to get a fuller picture of patients safety.

The rate of iatrogenic disease for NHS patients in hospitals and NHS patients consulting GPs and how we define it.

Iatrogenic disease is not quite the same as patients safety incidents or adverse events. Such definitions tend to overlap. We have defined PSIs above for the purposes of our NRLS.

To get estimates of rates in hospitals one can look at a number of international studies that have used reviews of patients' records to identify adverse events. Even these studies have used differing definitions and the range is from just under 2.9% to over 16% (10.7% in the UK study referred to above). The references for these studies are listed below.

  1. Brennan TA, Leape LL, Laird NM, Hebert L, Localio AR, Lawthers AG, Newhouse JP, Weiler PC, Hiatt HH. Incidence of adverse events and negligence in hospitalized patients. Results of the Harvard Medical Practice Study I.N Engl J Med. 1991;324:370-6.
  2. Wilson RM, Runciman WB, Gibberd RW, Harrison BT, Newby L, Hamilton JD. The Quality in Australian Health Care Study. Med J Aust. 1995 Nov 6;163(9):458-71.
  3. Wilson RM, Harrison BT, Gibberd RW, Hamilton JD. An analysis of the causes of adverse events from the Quality in Australian Health Care Study.Med J Aust. 1999;170:411-5.
  4. Thomas EJ, Studdert DM, Burstin H, Orav EJ, Zeena T, Williams EJ, Howard KM, Weiler PC, Brennan TA. Incidence and type of adverse events and negligent care in Utah and Colorado. Med care, 200;38:261-71
  5. Vincent C, Neale G, Woloshynowych M. Adverse events in British hospitals: preliminary retrospective record review. BMJ. 2001;3;322(7285):517-9.
  6. Davis P, Lay-Yee R, Briant R, Ali W, Scott A, Schug S. Adverse events in New Zealand public hospitals I: occurrence and impact. N Z Med J. 2002 Dec 13;115(1167).
  7. Davis P, Lay-Yee R, Briant R, Ali W, Scott A, Schug S. Adverse events in New Zealand public hospitals II: preventability and clinical context. N Z Med J. 2003 Oct 10;116(1183):U624.
  8. Baker GR, Norton PG, Flintoft V. Canadian adverse events study. CMAJ. 2004 Oct 12;171:834.
  9. Schioler T, Lipczak H, Pedersen BL, Mogensen TS, Bech KB, Stockmarr A, Svenning AR, Frolich A; Danish Adverse Event Study. Incidence of adverse events in hospitals. A retrospective study of medical records. Ugeskr Laeger. 2001 Sep 24;163:5370-8.

In general practice estimates are much less readily available. A recent review by Sandars and Esmail combined the data they were able to find to estimate that there may be between 5 and 80 patient safety incidents per 100,000 consultations in primary care but emphasised how different the definitions, purpose and methods of these studies were. They also suggest up to 11% of prescriptions involve error, again emphasising how different the studies and the definition of error were. See reference:

  1. Sandars J, Esmail A. The frequency and nature of medical error in primary care: understanding the diversity across studies. Fam Pract. 2003 Jun;20(3):231-6.

How are care episodes defined and how many care episodes were there in the NHS last year?

We do not hold this data. You should be able to get this information from the Department of Health or from the Office for National Statistics - see web site at

How many mistakes of any kind were made in these episodes?

This information is not directly available as described above.

I do hope you find this information helpful

Yours sincerely

Alison Pitts-Bland

Head of Media and Parliamentary Affairs