Dr. Karin Denton:

I agree that there are problems with looking at averages, which is what the programme has tended to do. It appears superficially that there are differences in the rates of certain categorisations from the various laboratories. The problem is that these differences are very difficult to interpret. There could be perfectly legitimate reasons for them. One of the things that makes it particularly difficult to interpret the data that CervicalCheck has collected, and is still collecting, is that it includes samples taken from colposcopies, which tend to be taken from women who are already known to have abnormal smears. This increases the rate of abnormality significantly, which means that the proportion of the slides which come from colposcopy determines the abnormal rate for that laboratory. Obviously, this is not satisfactory. That is why it has been recommended that the data specification should be altered to exclude such samples. A number of recommendations were made about improving the quality and robustness of data to allow for links with other factors which we know to have an influence on the rate of abnormality. If all of those recommendations are implemented, they will give a CervicalCheck a toolbox for making meaningful comparisons between the laboratories. I feel that should be a priority. It might transpire that there are differences which require further investigation, and such investigation might or might not indicate that there is a problem. CervicalCheck cannot start to discuss or consider that until it has robust data to work from in the first place.