Reply to: Breast screening is beneficial, panel concludes, but women need to know about harms. BMJ2012;345:e7330. Published 30 October 2012
Submitted as this Rapid-response: http://www.bmj.com/content/345/bmj.e7330/rr/614025
I was interested to read Nigel Hawkes report of the expert panel chaired by Michael Marmot looking at screening for breast carcinoma and the conclusion that “UK women invited to attend screening for breast cancer are three times as likely to be treated for a cancer that would never have harmed them as they are to have their lives saved.” They also conclude that ”clear communication to women of the harms and benefits is essential.”
In the past week I have learned of three new dementia “screening” initiatives all of which report benefits but make no mentions of harm:
(1) Reported on the front page of the Daily Mail: ‘Patients at risk will be able to do a series of tests on an iPad in the comfort of their local GP’s office. In only ten minutes the software can determine the difference between people with normal and abnormal memory.’ One such test being widely promoted is the CANTABmobile. It is highly sensitive in the diagnosis of mild cognitive impairment.
(2) The Dementia Services Development Centre have invited healthcare and non-healthcare professionals to a one-day course, provided across the UK, to provide ‘evidence based’ instruction ‘for diagnosing dementia early.’ This is based on a distributed model of assessment.
(3) In our local hospital it is now mandatory that anyone admitted over the age of 65 years undergo cognitive screening.
This may all sound like progress. However let us return to the lessons that we should learn from breast screening. Margaret McCartney asks: “If it looks like breast cancer screening is picking up more cancers, this is likely to include a lot of DCIS. But while DCIS is frequently diagnosed at screening, as we have seen, its progress is less certain. It does not always kill or even maim.” To paraphrase, if it looks like cognitive screening is picking up more dementia, this is likely to include a lot of mild cognitive impairment. But while mild cognitive impairment is frequently diagnosed at screening, as we have seen, its progress is less certain. It does not always harm or even progress.
The World Health Organisation, offer ten criteria for screening (here they include selective screening) and it is quite clear to me that at least two of these criteria are not met for screening of early dementia: Firstly we have “The natural history of the condition, including development from latent to declared disease should be adequately understood.” Mild cognitive impairment and early dementia overlap and both the patho-physiology and natural histories are ill-understood and beyond simplification. As Allen Frances has stated, the risk of false-positive diagnoses of dementia becomes extremely high the earlier one tries to detect memory loss. Most people had not heard of DCIS before this debate reached the wider press; I am sure that most people have not heard of mild cognitive impairment. The parallels are obvious.
Secondly the WHO ask that,”the test should be acceptable to the population.” Older adults deserve the same clear communication regarding the harms and benefits of cognitive screening as women choosing whether to undergo breast screening: so far there is virtually no discussion of informed consent in this context.
“ that morning we discovered just how preliminary we were. Which was some kind of progress, like they say realising one’s ignorance is the beginning of wisdom.”
 Blackwell, A. The use of CANTAB PAL in Alzheimer’s Disease, Chief Scientific Officer, Cambridge Cognition, 12 July 2011
 McCartney, M. The Patient Paradox 2012. Pinter & martin Ltd. p63
 Wilson J. M. G, & Junger, G Principles and Practice of Screening for Disease. World Health Organization 1968
 Frances, A. Psychology Today. Published 16 February, 2012
 Greig, A. In Another Light. Phoenix. 2004. Page 87