Prostate specific antigen (PSA) is a glycoprotein with a molecular weight of 34,000 which is located in the prostatic organization and seminal plasma. The PSA out of the blood increases with the occurence of prostate cancer, prostatomegaly, prostatitis and other prostatic diseases. Particularly blood PSA levels increase remarkably in patients with prostate cancer.
Antibodyadsorbed latex particles and PSA in the sample react immunologically, and causing the latex particles to agglutinate. This agglutination results in a change of turbidity, and the change in absorbance is a measure of the amount of PSA in the sample.