Among 206 men with serum PSA levels below the detection threshold, significant PCa was detected in 8 of 40 (20%) with serum PSA levels of 0.7 to 1.0 ng/mL, 12 of 59 with serum PSA levels of 1.1 to 2.0 ng/mL, p = 0.623, and 30 of 107 (28%) with serum PSA levels of 2.1 to 3.0 ng/mL, p = 0.011 regarding the other two subsets. This evidence concerns the gene KLK3 and posterior cortical atrophy.