PSA testing by GPs in New Zealand in 2010: can we learn anything new?


In New Zealand, over the past few years, there has been a considerable increase in the use of PSA testing in an (unorganized) attempt to increase the probability of the early identification of men at risk for clinically significant prostate cancer. And, as we all know, the application of the PSA test to “screen” populations for prostate cancer is controversial (to say the least).

Hodgson et al. have recently reported data on the application of PSA testing in five general practices (primary care practices) in the Waikato region in the North Island of New Zealand. Waikato has just one major city (Hamilton, with a population of > 200,000) and a number of smaller towns with populations up to about 20,000.

The authors’ goal was to examine the application of PSA testing in this sample of primary care practices in the region and to explore why the general practitioners (GPs) undertook PSA testing in specific individuals. To do this, Hodgson et al. collected data on PSA testing rates, reasons for testing, histology, and referral(s) to specialists for men of different age groups (all ≥ 40 years of age). They also distributed a questionnaire to all GPs to determine their views on PSA testing.

Here is what they found:

  • One in four men aged 40+ years had a PSA test in 2010.
  • Of these men,
    • 71 percent had no symptoms suggestive of prostate cancer or other prostate problems (i.e., they were asymptomatic)
    • >50 percent of men aged 70+ years were asymptomatic.
  • 10 percent of all PSA test results were “elevated” (but the definition of “elevated” is not given in the abstract of this paper).
  • 23 new cases of prostate cancer were diagnosed during the year.
  • 21/23 cases of prostate cancer identified were diagnosed following an elevated PSA test.
  • > 80 percent of men diagnosed with prostate cancer had prior medical histories of prostate pathology or lower urinary tract symptoms.
  • The questionnaire confirmed that
    • GPs believe in the benefits of using PSA to test for risk of prostate cancer.
    • GPs had difficulty in providing patients with information about the pros and cons of PSA testing.

There is relatively little published data on the application of PSA testing in the primary care community (in New Zealand or anywhere else that we are aware of). This paper appears to add only a little information to our current knowledge, but it is interesting to note that the majority of men diagnosed as a consequence of the use of PSA testing in this population-based sample of men in New Zealand were men who had some sort of medical history associated with the possibility of risk for prostate cancer, and that diagnosis of prostate cancer in asymptomatic men was rare.

However, there are other things that are not so clear about this study. For example, when the authors say that 1 in 4 men aged 40+ years had a PSA test in 2010, is this really 1 in 4 men out of the entire male population of Waikato or just 1 in 4 of the men who actually came in to see their GP in 2010? The latter seems more likely, and implies that the majority of these men were visiting the doctor with a specific purpose (i.e., they were exhibiting “health seeking” behaviors). If that is the case, then this is a self-selecting population sample and may undermine the study findings.

2 Responses

  1. The conclusion that sticks out like a sore thumb to my eye is not the one concerning prior medical history — it is the fact that 21/23 cases were diagnosed through an elevated PSA.

    The caveat is that we don’t know if the 23 constituted the total number of cases in the community, or those identified through this study … in which case the conclusion is tautologous!

  2. Dear Rick:

    It is clear that the 23 men diagnosed during the course of this study can only encompass the men in the community who actually went to see their GP during the course of the study.

    What is not at all clear (based on the publcly available abstract) is what percentage the total number of males in the community > 40 years of age actually went to see a doctor during the course of the study and were therefore exposed to the possibility of being given a PSA test. This information may well, however, be available in the full text of the article and would reflect multiple factors related to the knowledge and health-seeking behaviors of the males in this community

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