For a sensitivity of 90%, the equivalent specificity and likelihood ratios were: (i) measured PSA: specificity = 14.2%, LR = 1.05; (ii) 4 PSA-SNPs: specificity = 13.3%, LR = 1.04; (iii) 10 aggressive prostate cancer SNPS: specificity = 5.8%, LR = 0.96; and (iv) both (ii) and (iii): specificity = 16.8%, LR = 1.08. The gene discussed is KLK3; the disease is Familial prostate cancer.