Why is PSA considered to have good sensitivity but poor specificity for prostate adenocarcinoma?

Prostate-specific antigen (PSA) is a protein produced by both normal and malignant cells of the prostate gland. Its measurement is used as a tool for detecting prostate adenocarcinoma. The reason PSA is considered to have good sensitivity but poor specificity lies in its behavior in various prostate conditions.

Good sensitivity means that the test can effectively identify a high proportion of individuals who have prostate cancer, detecting elevated levels of PSA in many cases. This is crucial for early diagnosis and intervention. However, the specificity of a test refers to its ability to correctly identify those who do not have the disease. PSA levels can also be markedly elevated in conditions other than prostate cancer, such as benign prostatic hyperplasia (BPH), prostatitis, and other prostate diseases.

Therefore, the correct answer highlights that PSA can be elevated in prostate hyperplasia, which is a common non-cancerous condition affecting the prostate. This broad elevation in benign conditions lowers the test's specificity; thus, many individuals with elevated PSA levels may not necessarily have prostate cancer, making it less definitive as a sole diagnostic marker. Consequently, while PSA is useful for screening (good sensitivity), its ability to discriminate between malignant and benign diseases is limited (poor specificity).