Changes to screening programmes: why bridging is important!
Bell et al brilliantly stressed that screening in healthy subjects must be based on the strongest available evidence.(1) They illustrated this with the shift from guaiac to immunochemical tests for bowel cancer screening. Indeed, long term randomization is mandatory to allow comparison of clinically relevant benefits and harms. This is a key issue as marketing claims from the first round are not relevant for implementation of newer tests: a) positive and negative test rates are only surrogate endpoints; b) during first round screening prevalence of adenoma or cancer is maximal in the screened population. The sensitivity and the specificity may not be constant for subsequent rounds where the increased sensitivity could decrease and the specificity worsen.(2)
France wildly shifted from guaiac to immunochemical tests without debate on the need for long term randomization and without plan for the shift. 11,000 tests (estimate) from people that have made the screening with the guaiac test will be destroyed as they sent it after 31st January 2015.(3) No information yet on how people will be informed or who will do this. In the Alsace region 30,000 unused guaiac tests will be destroyed.(3) The new immunochemical test will be available on … April 14th.
1 Bell KJ, Bossuyt P, Glasziou P, Irwig L. Assessment of changes to screening programmes: why randomisation is important. BMJ 2015;350:h1566.
2 Braillon A. Can surrogate end points from a first-round screening be reliable for colorectalcancer screening? Gastroenterology 2012;142(3):e29.
Rapid Response:
Changes to screening programmes: why bridging is important!
Bell et al brilliantly stressed that screening in healthy subjects must be based on the strongest available evidence.(1) They illustrated this with the shift from guaiac to immunochemical tests for bowel cancer screening. Indeed, long term randomization is mandatory to allow comparison of clinically relevant benefits and harms. This is a key issue as marketing claims from the first round are not relevant for implementation of newer tests: a) positive and negative test rates are only surrogate endpoints; b) during first round screening prevalence of adenoma or cancer is maximal in the screened population. The sensitivity and the specificity may not be constant for subsequent rounds where the increased sensitivity could decrease and the specificity worsen.(2)
France wildly shifted from guaiac to immunochemical tests without debate on the need for long term randomization and without plan for the shift. 11,000 tests (estimate) from people that have made the screening with the guaiac test will be destroyed as they sent it after 31st January 2015.(3) No information yet on how people will be informed or who will do this. In the Alsace region 30,000 unused guaiac tests will be destroyed.(3) The new immunochemical test will be available on … April 14th.
1 Bell KJ, Bossuyt P, Glasziou P, Irwig L. Assessment of changes to screening programmes: why randomisation is important. BMJ 2015;350:h1566.
2 Braillon A. Can surrogate end points from a first-round screening be reliable for colorectalcancer screening? Gastroenterology 2012;142(3):e29.
3 Mascret D. [Cancer screening: thousands of tests lost.] Le Figaro 9 March 2015. Available at http://sante.lefigaro.fr/actualite/2015/03/09/23484-depistage-cancer-col... accessed 3 April 2015.
Competing interests: No competing interests