The expression of PSA mRNA and other validated biomarkers such as PCA3 in urine and blood are far more suitable for diagnosis but they also have drawbacks and limitations in terms of ease of sample handling. This is because they require the urine sample to be immediately frozen, otherwise nucleic acids may be broken down before they can be detected.
Stabilization of mRNA in Urine to Aid Diagnostic Tests for Prostate Cancer
source: News Medical