The Acid Phosphatase test measures the level of acid phosphatase enzyme in the blood, specifically from two sources: total acid phosphatase (from various tissues) and the prostatic fraction (from the prostate gland). It is primarily used to help diagnose or monitor prostate cancer, especially when evaluating metastasis. Elevated prostatic acid phosphatase levels can indicate prostate carcinoma, while total acid phosphatase can rise due to liver disease, bone disorders, or certain cancers.