Authors’ replyBMJ 2011; 342 doi: http://dx.doi.org/10.1136/bmj.d3710 (Published 14 June 2011) Cite this as: BMJ 2011;342:d3710
- Gabriel Sandblom, associate professor1,
- Eberhard Varenhorst, professor2,
- Johan Rosell, statistician3,
- Owe Löfman, professor4,
- Per Carlsson, professor5
- 1CLINTEC, Karolinska Institute, 141 86 Stockholm, Sweden
- 2Department of Urology, Linköping University Hospital, Linköping
- 3Oncology Centre, Linköping University Hospital, Linköping
- 4Department of Mathematical Science and Technology, Norwegian University of Life Sciences, 1432 Aas, Norway
- 5Center for Health Technology Assessment, Linköping University, Linköping
In answer to Burn and colleagues1:
(1) The decision to exclude men older than 69 was taken towards the end of the study to avoid overdiagnosis in older men. Even if this could have been done consistently from the beginning, the increasing age of the study population during the first three screening rounds would not affect the outcome substantially.
(2) To investigate whether the detection rate and subsequent mortality changed after the introduction of prostate specific antigen (PSA) testing, we modelled diagnosis before 1993 versus diagnosis after 1993 as a dichotomous time-varying covariate. We found no significant difference in mortality.
(3) The problem of false positive findings at the primary investigation has been analysed.2
(4) Although we did not address predictive values, they have been considered briefly before.3
(5) The figures indeed showed survival only …
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