The Commission for Health Improvement has admitted to an error in the way it calculated patient deaths for some of its early clinical governance reviews and, in so doing, wrongly criticised a trust for having death rates much higher than the national average.A CHI spokesperson said: 'The information we were using was from the Department of Health, but it only counted deaths from the first patient episode.'That meant CHI failed to take account of people who had died after being referred to another consultant.As a result, Chesterfield and North Derbyshire trust was told that its mortality rates in emergency medicine were 30 per cent above the national average.The audit was then broadened from surgery to include medicine.Trust chief executive Avril Johns criticised CHI for making such a basic error and has raised the matter with CHI chief executive Dr Peter Homa.