KLK3 and prostate cancer: In the United States (Dyche et al, 2006), referral rates were studied from 1998 to 2004 in men aged ⩾75 years with no previous prostate cancer diagnosis attending one centre in Iowa: in those with PSA levels between 0.1 and 4.0 ng ml−1, 28.6% were referred, and in those with PSA levels >4.0 ng ml−1, 52% were referred.