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Student: Charlotte Duncan
Supervisor: Dr Paul Corwin, Dr Dee Richards
Sponsor: Otago Theme Bursary, University of Otago

Prostate cancer is an area of great controversy in the medical world at present. The debate revolves around the use of the PSA test in screening men without symptoms for prostate cancer. In essence, it is not yet known whether screening with PSA tests reduces the number of men dying from prostate cancer. In addition, the role of potentially serious side effects due to further investigation and treatment needs to be determined. At present there are large studies underway to determine the answer. In the meantime doctors worldwide are left managing as well as they can with inadequate information. At the same time, use of the PSA test is increasing.

The aim of this study was to determine what is driving the increased use of such a controversial test.

With the help of the Pegasus Health group, we identified those general practitioners (GPs) that were high or low users of PSA tests. To these GPs we sent questionnaires and also asked permission to access other laboratory data.

We found the two groups of GPs quite diverse. The high users were more likely to support a population screening program for prostate cancer. This opinion was passed onto patients, with this group being more likely to recommend the PSA test to their patient. However there was no difference in the tendency to bring up PSA screening between the two groups; suggesting the low users of PSA testing also felt the need to discuss PSA, even if they were to discourage the patient from taking the test.

The influences behind these differences were quite contrasted. More of the low PSA users found the local GP education program, with a broader population health emphasis, to be their strongest influence; while more high users referred to their own clinical experience as well as the opinion of local specialists.

Advice most GPs in both groups considered important to pass onto their patients included discussing the inaccuracy of the PSA test, the consequences of further investigation and treatment, and, discussion of the symptoms and risk factors for prostate cancer. There is a pamphlet available on this issue for patients, which both groups were unlikely to pass on to the patient. Reasons stated a lack of supply or knowledge of the pamphlet, although some GPs cited disagreeing with the content.

Finally we compared lab data between the two groups for use of other preventive tests. The only difference between the two groups was that the low users of PSA were higher users of mammography tests, a well supported screening test.

This study shows a polarization of GP's opinions and use of PSA testing. Different influences point to a dichotomy between sources of information – personal experience versus a population based approach, which is consistent with the current debate. This reinforces the importance of GP opinion on practice. PSA testing over the past 3 years also reflects the role of patient opinion. While there seems to be a different 'set point' depending on GP opinion, in both groups a steady and similar rise in PSA testing can be seen.

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