‘Reliable information on deaths by cause is an essential input for planning, managing and evaluating the performance of the health sector in all countries.’
With these words Murray and Lopez introduced their chapter on the causes of death in the book The Global Burden of Disease.1 The statement is equally true when considering diseases that do not usually cause death. They went on to consider what was meant by the words ‘reliable’ and ‘cause’ and examined protocols for assigning cause, disease classification, age standardisation and other factors important to the recognition of difference, be that between countries and regions, groups of individuals within a country, or differences over time. Although the performance of the health sector was an important element of their deliberations, when evaluating change we must never lose sight of the persons who die or experience disease but do not consult. Changes in sickness certification for example have knock on effects on consulting patterns.
The initial priority in any comparison is to establish the fact of change and this should precede efforts to interpret the reasons for change. Routine healthcare data are collected for a particular purpose and they are not always appropriate to describing change. The introduction of the Quality and Outcomes Framework in the British NHS has had fundamental effects on the ways doctors record information.2 Differences between the before and after situation do not necessarily indicate fundamental changes in the health problems of the subjects monitored or the way in which they have been managed: sometimes the main change is in the way the information is recorded. Mathematical techniques such as age standardisation and statistical estimation of confidence intervals enhance our ability to make comparisons but are only appropriate if monitored samples are truly representative of the population. When interventions are considered, …