*Risk-adjusted mortality*

*3.11 Risk adjustment using the UKCTA risk model reduced the difference between the observed and expected number of deaths within 30 days at Harefield and at other UK centres in 2008. The centre effect estimate for Harefield reduced by more than 50% with risk adjustment and the UKCTA analysis found that "although mortality at Harefield remained 52% higher than expected using the risk model, the number of cases was low and Harefield was not identified as significantly divergent."* 

#### *Sequential monitoring of mortality*

*3.12 The sequence of deaths in July and August 2008 was enough to cause the more sensitive technique of sequential monitoring using cumulative sum (CUSUM) method to signal an alert for*  *30-day mortality at Harefield. The signal occurred after Harefield had contacted the NSC Team as the charts are produced on a monthly basis when the 30-day follow-up point has passed.* 
