Balancing sensitivity and specificity: sixteen year's of experience from the mammography screening programme in Copenhagen, Denmark.
OBJECTIVE
To report on sensitivity and specificity from 7 invitation rounds of the organised, population-based mammography screening programme started in Copenhagen, Denmark, in 1991, and offered biennially to women aged 50-69. Changes over time were related to organisation and technology.


METHODS
Individualized data were retrieved on outcome of screening mammography, assessment, surgery, and interval cancers. European Guideline performance indicators were calculated, supplemented with false positive and interval cancer rates per 1000 screens. False positive tests were divided into those sorted out at assessment (Type 1) and at surgery (Type 2).


RESULTS
In total, 1392 invasive breast cancers/ductal carcinoma in situ cases (DCIS) were diagnosed, giving an overall detection rate of 7.6 per 1000 screens. Of 5178 false positive tests, 4666 were Type 1 and 512 Type 2. The 468 interval cancers constituted 25% of all breast cancers (=screen detected+interval cancer). Almost all outcome measures were well within the desirable level of the European Guidelines. Risk of Type 2 false positive tests was positively associated with detection rate especially at initial screen, and interval cancer rate was negatively associated with detection rate. This association was decoupled after introduction of high resolution ultrasound and stereotactic breast biopsies, resulting in a Benign-to-Malignant-Ratio (BMR) of 1:11.40.


CONCLUSIONS
Mammography screening is a delicate balance between benefits and risks. Increase in detection rate came at cost of increase in risk of benign biopsies. Introduction of new technologies broke this pattern and a slight increase in detection rate coincided with an unprecedentedly low BMR.
Institute of Public Health, University of Copenhagen, Østre Farimagsgade 5, DK 1014 Copenhagen K, Copenhagen, Denmark. nicolaiuf@gmail.com
Nicolai
N
Utzon-Frank
Ilse
I
Vejborg
My
M
von Euler-Chelpin
Elsebeth
E
Lynge
D000368:Aged; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000401:mortality / Q000517:prevention & control; D018270:Carcinoma, Ductal, Breast / Q000175:diagnosis* / Q000401:mortality / Q000517:prevention & control; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000175:diagnosis* / Q000401:mortality / Q000517:prevention & control; D003718:Denmark; D055088:Early Detection of Cancer; D005260:Female; D006801:Humans; D008327:Mammography; D008403:Mass Screening; D008875:Middle Aged; D011379:Prognosis; D012680:Sensitivity and Specificity; D015996:Survival Rate; D013997:Time Factors