Annex A > Chapter 19 - Statistics Relating to the Clinical Performance of Paediatric Cardiac Surgical Services in Bristol Compared with Other Specialist Centres during the Period 1984 to 1995 > Introduction: purpose and scope of the chapter

Introduction: purpose and scope of the chapter

This chapter sets out the evidence received by the Inquiry on statistics relating to the clinical performance of paediatric cardiac surgical services in Bristol relative to other specialist centres.

In this chapter, the term `clinical performance' means the activity (the type and volume of operations or procedures carried out) and outcomes (in terms of post-operative mortality and morbidity) of paediatric cardiac surgical services in Bristol. Bristol's particular clinical performance may be assessed by examining its own results over a period of years and by comparing them with the contemporaneous performance of other centres.

`Statistics', for the purpose of this chapter, means figures of any kind relating to clinical performance.

The statistics fall into two main categories:

• statistics relating to clinical performance that were available to clinicians in Bristol during the period 1984 to 1995 (the clinicians'contemporaneous statistics);
• statistics relating to clinical performance presented to the Inquiry as expert evidence (the Inquiry's retrospective statistical evidence).

As regards the clinicians'contemporaneous statistics, the main sources of statistics relating to clinical performance available to clinicians in Bristol during the period 1984 to 1995 were:

• the clinicians'own clinical logs and computerised information systems;
• external sources, including the Society of Cardiothoracic Surgeons' UK Cardiac Surgical Register (`UKCSR'); the reports of national working parties on neonatal and infant cardiac surgery; ad hoc external audit reports; and professional meetings, contacts and journals.

As regards the Inquiry's retrospective statistical evidence, [1] Experts were commissioned to review, analyse and synthesise the six principal sources of data that existed at the relevant time. These were: the national Hospital Episode Statistics (HES); the UKCSR; the UBH/T's Patient Administration System (PAS); the clinical records of children whose treatment fell within the Inquiry's Terms of Reference; the surgeons' logs; and the South West Congenital Heart Register. [2]

The statistical investigations described in this chapter make comparisons with other centres. They do not seek to draw conclusions as to the reason(s) for any difference which may be found to exist between Bristol and other centres providing similar treatment. Rather, they seek to establish, on a statistical basis, whether there is such a difference, and how significant that difference is. The experts in their investigations examined a number of suggested causes of such differences as are identified, and expressed their view that some of these proposed causes may be eliminated or discounted. They did not advance any reason for the differences which they identified.

The statistical evidence received by the Inquiry must be distinguished from the Clinical Case Note Review (CCNR), reproduced in Annex B. The CCNR was a clinical audit by experts which focused on the quality of care delivered in a sample of cases in Bristol, as judged by reference to the case notes. The CCNR examined a representative sample of case notes, with a view to generalising from the conclusions drawn from the sample to the whole. The conclusions are derived from what the notes show about the care provided at the different stages of a child's treatment. The experts' views as to what might have been expected elsewhere informed their conclusions, but formal comparison of Bristol with other centres formed no part of the CCNR exercise.

The chapter is divided into two main parts. The first part sets out evidence received by the Inquiry concerning the nature of the statistics relating to clinical performance available to clinicians in Bristol during the period 1984 to 1995, and the views of the Inquiry's experts on the interpretation of these statistics. The second part sets out the principal conclusions of the retrospective statistical evidence received from the Inquiry's experts relating to the activity and outcomes of paediatric cardiac surgical services at Bristol relative to other specialist centres, and the views of the Bristol surgeons and of the experts on the reliability and validity of this statistical evidence.

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Footnotes

[1] The Experts' statistical reports appear in full in Annex B

[2] The log kept by the perfusionists in Bristol and the mortality records of the Office for National Statistics were also used by the Experts, for the purpose of testing the accuracy of the data derived from the main sources