Dr. Karin Denton:

There are two separate issues involved. The figures at which we can look are not telling us about the women with cancer who are being missed. They are telling us about the proportion of women who have abnormalities detected. The majority will not have cancer, but there will be changes which, if left untreated, might at some point over many years develop into cancer. It is not an absolute measure of a laboratory's ability to prevent cancer from developing, but it is a reasonable surrogate because they are data that are relatively easy to get and are current.

Much of the problem is that when there is a look-back, many of the samples in respect of which the diagnoses were altered may have been taken many years before. Although it tells us something useful, it does not necessarily tell us how a laboratory is functioning today. It is important to keep the two matters separate. There is no measure of how likely it is a laboratory will miss a diagnosis that will lead to cancer in a sample reported today. We simply cannot measure it. As a surrogate, we look at how good they are in detecting precursor abnormalities today, which we can do.

On real-time monitoring, that is the best we can do. The audit tells us something different, which is what it should be doing from the point of view of improving laboratory practice, namely, identifying samples where a diagnosis was missed. It could have been difficult, as Dr. Gabriel Scally said, but could then be used to feed into training and supervision. I would think it would be unusual for a poorly performing individual member of staff to be detected through the audit because it would be too late. They already have been reporting for five years at that point. Accordingly, many of the quality assurance measures at which we look are process measures such as how does one check up on members of staff, monitor their performance and detect problems in real time. That is what one needs to do to improve the service.