Spurious trends in coronary heart disease incidence: unintended consequences of the new GP contract?

Comparisons of the same patient data in 2004 and 2006 downloads of the DIN-LINK UK primary care database demonstrated unexpected differences in the rates of coronary heart disease between the datasets. Incidence rates were lower between 1996-2003 in the new (2006) download. Patient record checks demonstrated that coronary heart disease codes had been removed in the new download during the run-up to the new contract. Planners need to be aware of such issues when evaluating trends in CHD or other similar conditions.