KLK3 and posterior cortical atrophy: However, only 25% of men with elevated PSA levels are diagnosed with PCa because of the poor specificity of PSA, which means that 75% of patients undergo unnecessary and potentially harmful follow-up tests, such as biopsies, especially for men with PSA values between 4.0 and 20.0 ng/mL (low and medium clinical risk category) [3].