The PSA and relative vs. absolute risk

If PSA screening reduces the death rate from prostate cancer by 20%, why is there so much debate about the test's effectiveness? It's because that one number doesn't tell the whole story, Tabitha M. Powledge writes. A more realistic interpretation of the latest results from the European study of routine PSA screening, she writes, would describe the benefit for an average middle-aged man as a drop in risk from about 3% to about 2.4%. Also, hyping the human microbiome.