This heterogeneity may be explained in part by differences in tumor grading systems by urologists in different countries, as well as by different patient recruitment criteria for the different sample sets - for example, the Australian patient samples were pathology-confirmed patients who presented with symptomatic disease, whilst the UK GWAS stage 1 samples were detected by PSA screening and were also enriched for early onset disease or patients with familial history of prostate cancer. Here, KLK3 is linked to prostate carcinoma.