currently , serum is used more often than urine to detect prostate specific antigen . the need for a non - invasive test yielding similar results led us to develop a urine test that uses solar irradiated water as a reactant species . to develop this technology , seven reagents plus one control were produced by exposure of water for 40 days in sunlight to the colors of the visible spectrum through colored cellophane , control being an unwrapped bottle of sterile water . serum psa and the urine was tested using the above reagents . a positive urine test was observed with yellow - filtered irradiated water which absorbed at 454 nm . positive results for the urine test had psa levels of 0 . 21 - 4 . 0 ng / ml . thus , this invention describes a non - invasive urine test mainly positive with psa 0 . 21 - 4 . 0 ng / ml .