National Congenital Heart Disease Audit (NCHDA)
The National Congenital Heart Disease Audit (NCHDA) was set up in 2000, when known as Central Cardiac Audit Database (congenital), to assess outcomes after therapeutic paediatric and congenital cardiovascular procedures (surgery, transcatheter and electrophysiological interventions) in the UK and the Republic of Ireland (since 2012). It is the largest comprehensive national audit of its kind in the world, with over 120,000 patients in the database (60% post-surgery). Data submission is mandatory and is collected from all centres undertaking such procedures in children and adults. In 2011 the audit moved from being part of the NHS Information Centre, to being one of six audits under the auspices of the National Institute for Cardiovascular Outcomes Research (NICOR)
, an independent entity within University College London. NICOR’s mission is to provide accurate data on cardiovascular outcomes for the public, healthcare providers and the medical profession in order to drive up the quality of care and outcomes for patients. The NCHDA is commissioned and funded by the Healthcare Quality Improvement Partnership, on behalf of NHS England, as part of the National Clinical Audit Programme, and is clinically led by the BCCA and SCTS.
The NCHDA focuses on monitoring activity levels and outcomes following cardiovascular procedures with an aim of improving the quality of specialist congenital cardiovascular care by providing reliable, risk adjusted and independently validated data, including individual procedural counts, activity levels, access to high quality fetal cardiology screening for antenatal diagnosis, and most importantly, patient outcomes with respect to mortality and postprocedural complications. Since 2007, the audit has published detailed results on the NCHDA portal
. The underlying principle is that the audit compares levels of centre performance, so as to set standards of optimal care as a benchmark for individual hospitals. Units found to be relatively underperforming will receive constructive feedback, which might focus on, for example, surgical techniques, intensive care support, or shortcomings in the ‘system’ or infrastructure.
Patients, parents and carers, as well as clinicians and commissioners, are encouraged to regard the facts and figures available on the NCHDA website as a useful source of information.
This knowledge can then be used together with information received from the family doctor and heart specialist when making decisions on treatment options. Part of the audit data is also available for viewing via the website ‘Understanding Children’s Heart Surgery Outcomes
’, which aims to help make sense of the survival statistics used when analysing outcomes following children's heart surgery.
Details of NCHDA processes and analyses
This is mandatory for all relevant procedures at all institutions undertaking paediatric and adult congenital cardiovascular procedures, aiming for 100% case ascertainment. Data is collected electronically in an encrypted format as a 42 field minimum dataset, with informed patient consent. A common clinical coding language is used for all submissions: the European Paediatric Cardiac Code (a subset of the International Pediatric and Congenital Cardiac Code
Verification of life status and validation of data
Independent validation of the patient’s life status (alive or dead) is achieved by central tracking using the linkage of each patient’s NHS number to the Office for National Statistics, where the life status of every resident in England and Wales is independently registered. The NCHDA is therefore regularly updated on patients’ survival status. Separate arrangements exist in Scotland, the Republic and Northern Ireland. It is important to note that if a centre undertaking a procedure records a death, then this is taken as fact, even if central mortality tracking is still recording an alive status due to legal process delays, such as delay in registration whilst awaiting the results of an inquest. The system, therefore, allows for patients to be tracked, irrespective of changes of address or hospital, minimising the chances of being lost to follow-up, at least in terms of life status.
In addition, the audit uses a rigorous validation process comprising annual site visits during the 7 months following the data submission year (1st April to 31st March), by an independent clinical data auditor and volunteer clinician to ensure full case ascertainment and to validate the accuracy of the data submitted. Submitted data are also signed off and verified by each local hospital as being accurate by backwards checking with the NCHDA database. At the visit, all operation and catheter logbooks or electronic records are scrutinised to ensure procedural data accuracy and that all procedures have been captured. In addition, a random selection of 20 patient hospital records undergo detailed analysis of all submitted data fields, comparing to the dataset, noting missing or incorrect data. A percentage Data Quality Indicator (DQI) score is then calculated. Typically, NICOR would expect the DQI to be great than 90%. Finally the records of all deceased patients are examined to ensure the accuracy of diagnoses, procedure(s) undertaken and any additional comorbid factors, again comparing against the data submitted.
Risk adjusted outcomes
Risk adjustment methodology is a process used to account for the impact of individual risk factors, such as the type of procedure itself with its inherent risks, age, coexistent conditions such as syndromes, severity of illness and other medical problems that can put some patients at greater risk of adverse outcomes than others. Risk adjustment is a crucial part of reporting the results of procedures on children and adults born with congenital heart disease (CHD), due to the large number of different malformations, singly and in combination, that may be present, and the corresponding large number of possible therapeutic procedures used to treat the condition. The NCHDA therefore reports the results of 72 surgical, transcatheter cardiovascular and electrophysiological interventional procedures as a form of risk stratification by procedure type, using funnel plot methodology. The types of procedure undertaken at each hospital varies and a full list of procedures including a glossary describing each procedure, is available on the NCHDA web portal
Partial Risk Adjustment in Surgery (PRAiS)
NCHDA also uses this specifically designed and validated software to report risk adjusted whole centre outcomes. PRAiS estimates the risk of death within 30 days of a primary surgical procedure in a paediatric patient (< 16 years), based on the specific procedure, age, weight, the patient’s recorded diagnoses, and comorbid conditions that may be present. The software was updated in July 2016 to PRAiS2, with its empirical calculations based on more recent national outcomes (2009-15). The new risk model generated incorporates a more sophisticated approach to dealing with the operative risks linked to comorbidity and severity of illness
. For more detailed explanation of risk adjustment and PRAiS software, visit the website Understanding Children's Heart Surgery Outcomes
. PRAiS was created specifically to enable in house, near real-time quality assurance and monitoring of whole program activity, so as to answer the major criticism of historical reporting of outcomes on operations, which may date from 1-2 years earlier. The software generates a Variable Life Adjusted Display (VLAD) chart covering the period of the data and allows hospitals to quickly identify trends in outcomes (positive or negative) for in-house discussion at monthly multidisciplinary team meetings and that might warrant further investigation. All specialist paediatric centres currently use PRAiS and it is also a metric submitted quarterly to the Quality Dashboard
monitored by Specialist Commissioners and the Congenital Heart Services Clinical Reference Group.
All NCHDA reports of 30 day survival outcomes for quality assurance, along with the identification of potential outlier institutions, are published in rolling three yearly cohorts, due to the relatively low numbers of patients undergoing any specific procedure and the theoretical very small risk of identifying individuals. The audit uses two statistical control limits for its analyses (note, these percentages are not related to actual survival figures): an alert limit (97.5%) and an alarm limit (99.9%). If a unit’s risk adjusted outcomes are above (i.e. ‘better than’) both limits then their performance is not statistically different from the national average.
Poor antenatal diagnosis rates suggest that there is reduced opportunity for comprehensive counselling during pregnancy for parents expecting a baby with significant CHD, as well as compromising the ability to deliver optimal care for such infants following delivery. Failure to recognise and promptly treat major CHD is associated with increased morbidity and mortality rates, and is recognised as an important quality-of-care issue. Since 2003, the NCHDA has collected data on whether the heart abnormality for which a procedure in infancy was undertaken was detected antenatally. Reporting on the success of antenatal diagnosis of severe CHD at a regional level, is undertaken in order to target quality improvement efforts, such as thorough training and optimising sonographic equipment. There has been a year on year consistent quality improvement in antenatal detection rates since 2003 from 24% to nearly 50% currently, noting differences between countries and regions within the UK and Ireland. This is an excellent demonstration of how quality of care can be improved for any clinical outcome measure using a validated national database which publishes its results on a public, web-based portal
, and permits a degree of ‘naming and shaming’ to drive improvements.
NCHDA is a valuable resource for the exploration of trends in outcome. A recently published trend analysis of over 36,600 surgical episodes undertaken in 10 consecutive years from April 2000 to March 2010, demonstrated a fall in 30 day raw mortality from 4.3% in 2000-01 to 2.6% in 2009-10 (April to March). This coincided with a significant increase in the number of paediatric CHD procedures undertaken in the UK (2,283 in 2000-2001 to 3,393 in 2009-2010). These UK results compare favourably with international similar era results from North America and Europe with a reported mortality of over 4%. Importantly, case mix, as assessed using four risk bands of estimated mortality calculated using PRAiS methodology, progressively increased in this decade, notably in terms of the numbers of patients weighing less than 2.5kg and those with a high risker diagnosis such as hypoplastic left heart syndrome. Concerns that the publication of comparative unit specific 30 day mortality outcomes might lead to risk averse behaviour by individual surgeons or centres appear to be unfounded in the UK.
[Content provided by Dr Rodney Franklin, Clinical Lead NICOR National Congenital Heart Disease Audit, Consultant Paediatric Cardiologist, Royal Brompton & Harefield NHS Foundation Trust - last updated 21 November 2016]