As of 2006-07, published outpatients tables were accredited as a National Statistic. This means the data within these reports have been produced in accordance with the Code of Practice for Official Statistics. This does not apply to the outpatient dataset as a whole because some quality and coverage issues remain with certain fields which do not feature in the published tables.

The outpatients dataset contains individual records for all outpatient appointments occurring in England. It is compiled from data sent by NHS trusts and primary care trusts (PCTs) in England. Data is also received from a number of independent sector organisations for activity commissioned by the English NHS.

HES outpatient data was collected for the first time in 2003-04 and first published in 2006 as an experimental statistic. Over time the data quality has gradually improved. However, the coverage and completion of some fields in the outpatient dataset still remains quite poor. For more information please see the outpatient data quality reports.

Some fields are mandatory (providers are expected to complete and submit them), but others are optional. Optional fields include diagnosis and procedure, with the majority of records submitted as unknown. For a full list of mandatory outpatient fields, please see Appendix C in the Outpatient Data Quality Report, 2007-08.

The NHS Information Centre for health and social care liaises closely with organisations to encourage submission of complete and valid data, and seeks to minimise inaccuracies and the effect of missing and invalid data via HES processes.

From 2008 a Data Quality Dashboard became available on the Connecting for Health website. The Data Quality Dashboard, which is updated monthly, is a national resource to support improvement and completeness of all commissioning dataset (CDS) dataflows to the Secondary Uses Service (SUS). This includes the outpatient CDS as well as the admitted patient care and accident and emergency datasets. The dashboard can be used by organisations to review the data they've submitted from their PAS systems to SUS to ensure that the data is comprehensive, compliant with data standards, complete and accurate.

The coverage and completeness of the fields used to derive HES time waited figures has remained relatively stable over time. However, the differences and limitations in how time waited is calculated still remains.

HES time waited figures:

• measure the time waited for those who have attended their first outpatient appointment over the course of the year, ie who have completed their wait
• calculate the difference between the outpatient appointment date and either the referral request received date, last non-attended appointment or patient cancellation date.

The inclusion of non-consultant activity in HES data may also be partly responsible for the difference in figures. As such, patients may not have benefited from waiting time targets.

The Department of Health is the official source of data on 18-week referrals. This data is available at a regional level and currently at specialty level. HES time waited figures allow for more in-depth clinical analysis. Note, however, that coding of procedures and diagnoses in outpatients is known to be poor.

For more information on the monitoring of the 18-Week Waits, please see the Department of Health's 18 Weeks Referral to Treatment (RTT) Statistics website.

To ensure the NHS is working towards achieving the 18-week target, a mandatory national data collection to monitor RTT (referral to treatment) times was introduced on 1 January 2007. Currently the NHS submits aggregate RTT data to the Department of Health (DH) via Unify, DH's online data collection system. The introduction of CDS Version 6 in April 2008 included RTT data items to enable the monitoring of the achievement of the 18-Week Wait target through SUS. This allows the progress of individual patients to be measured and tracked along the RTT pathway and drill-down analysis to local and specialty level. Once the data quality of this field improves it will be available for analysis in HES.

For all outpatients dataset changes, please see the Connecting for Health's Data Set Change Notices (DSCN).

NHS Comparators is a free comparative analytical service that enables commissioners and providers to improve the quality of care delivered by benchmarking and comparing activity and costs on a local, regional and national level. NHS Comparators looks at a whole range of activity: inpatient, outpatient and disease-specific.

There are a series of outpatient indicators available on NHS Comparators, such as the total number of attendances per 1,000 people or the percentage of patients who did not attend their outpatient appointment.

For more information please see the NHS Comparators website.

There are now a limited number of treatment functions in outpatients that are paid via the tariff. The outpatient's tariff is based on attendance by treatment function. Reference cost categories were mapped to the appropriate outpatient tariff treatment function. Procedures in outpatients are currently non-mandatory in 2009-10. For a list of treatment functions and procedures on the paid via tariff, please see the Outpatient Data Quality Report, 2007-08.

In part this relates to women's greater life expectancy, but also to the use of antenatal clinics during child-bearing years. Women are also less likely to fail to attend their appointment.

This enables multi-professional business and training to occur on this weekday.

Patients can have more than one condition which requires onward referral or require joint treatment by more than one consultant. Initially patients may also be referred inappropriately, which results in onward referral.

Between the ages of 0 to 44 years old, men are more likely to be referred to outpatient trauma and orthopaedic clinics. After this age, women are more likely to be referred to these clinics. The likely explanation for this is that boys and young men tend to be more accident prone, while older women can have brittle bones, which are more likely to be injured in accidental falls.

Non-surgical patients are more likely to have chronic or deteriorating conditions requiring continuous attendance at a clinic. Surgical patients are often more acute but recover quickly after an operation.