How should we measure psychological consequences of false-positive screening mammograms adequately?
In this week's EBM, Bond and colleagues report a systematic review entitled: 'Psychological consequences of false-positive screening mammograms in the UK'.(1) Their two main outcomes are self-reported questionnaires, and attendance at the next screening round.
Together with two colleagues, I conducted a systematic review in 2004 on the adequacy of measurement of short and long-term consequences of false-positive screening mammography.(2) We concluded that the generic measures (GHQ, HADS and STAI) "should not be used to measure psychological consequences of any kind of cancer screening" and that a condition- specific measure (PCQ) was preferable.(2) We also concluded, "Given the inadequacy of the measurement instruments used, any current conclusions about the long-term consequences of false-positive results of screening mammography must remain tentative."(2) Therefore, we conducted six focus group interviews to test the content validity of the PCQ in a time frame of 1-12 months after a false-positive screening mammography.3 Because we had to make major changes to the PCQ, we developed a new questionnaire: Consequences Of Screening in Breast Cancer (COS-BC).(3) We have validated the COS-BC using the Rasch Item Response Theory model and found that the measure is a reliable multi-dimensional instrument for short- and long- term psychosocial consequences of false-positive screening mammography.(4;5) Therefore, it is unfortunate that Bond and colleagues do not discuss the inadequacy of the psychological measures included in their systematic review, and that a valid and reliable self-reported outcome measure with high content validity does exist. The inadequacy of the generic measures included in Bond et al's review could also be a plausible explanation as to why they found that: "Heterogeneity was such that meta- analysis was not possible".
It is also difficult to understand why Bond and colleagues have limited their review only to include trials conducted in the UK. Why should we expect different psychological reactions to a false-positive screening mammography in different countries? The COS-BC has been translated, adapted, and tested for relevance in a Swedish context, and we found essentially no differences in psychosocial consequences of false- positive screening mammography in Denmark and Sweden.(6) Together with other colleagues, I have conducted the same translation, adaptation, and test of relevance of the COS-BC in Norway, the Netherlands, and Germany, with the same result as in Sweden (these projects are in progress).
The second outcome of Bond and colleagues is attendance to the next screening round after a false-positive mammography. In some countries, researchers have found that these women have a higher attendance to the next screening round than those with a normal screening result. In other countries, researchers have found the opposite, or similar attendance rates. In my qualitative single- and focus group-interviews, some women said that they did not dare to go to next screening after all they had experienced after a false-positive result.(4) Others said they did not dare to stay away.(4) If the psychological impact of a false-positive screening mammography can be ambivalent feelings about attendance to the next screening round, re-attendance is a poor surrogate outcome for the psychological impact of a false-positive screening mammography.
(1) Bond M, Pavey T, Welch K, et al. Psychological consequences of false-positive screening mammograms in the UK. Evid Based Med 2012.
(2) Brodersen J, Thorsen H, Cockburn J. The adequacy of measurement of short and long-term consequences of false-positive screening mammography. J Med Screen 2004;11(1):39-44.
(3) Brodersen J, Thorsen H. Consequences Of Screening in Breast Cancer (COS-BC): development of a questionnaire. Scand J Prim Health Care 2008; 26(4):251-256.
(4) Brodersen J. Measuring psychosocial consequences of false- positive screening results - breast cancer as an example. Department of General Practice, Institute of Public Health, Faculty of Health Sciences, University of Copenhagen: M?nedsskrift for Praktisk L?gegerning, Copenhagen. ISBN: 87-88638-36-7; 2006.
(5) Brodersen J, Thorsen H, Kreiner S. Validation of a condition- specific measure for women having an abnormal screening mammography. Value in Health 2007;10(4):294-304.
(6) Bolejko A, Wann-Hansson C, Zackrisson S, et al. Adaptation to Swedish and further development of the 'Consequences of Screening - Breast Cancer' questionnaire: a multimethod study. Scand J Caring Sci 2012.
Conflict of Interest: