Serum Acid Phospatase

Serum acid phosphatase (ACP) is an enzyme that hydrolyzes phosphate esters optimally at acidic pH. It’s produced mainly by the prostate but also by liver, bone, spleen and red blood cells. Measured in blood, serum ACP has been used to monitor prostate disease; elevated levels can indicate prostate cancer, bone or liver disorders, or hemolysis, and results vary by age, sex and lab method.

High acid phosphatase indicates increased release of this enzyme from tissues, commonly the prostate, and can suggest prostate conditions (prostatitis, benign enlargement, or prostate cancer). It may also rise with bone disorders, liver disease, certain blood disorders, or tissue damage. Results need clinical correlation and further testing (PSA, imaging, or biopsy) to determine the cause.

Acid phosphatase is a blood enzyme test that measures activity of acid phosphatases (including the prostatic isoenzyme). It’s used to help detect and monitor prostate disease (including cancer), assess certain bone or liver disorders, and in forensics to detect semen. Elevated levels can indicate prostate enlargement, metastasis, bone or liver involvement, or hemolysis; isoenzyme testing clarifies the source.

Acid phosphatase (particularly prostatic acid phosphatase, PAP) can be elevated in prostate cancer and its bone metastases, but it is not specific and can rise with benign bone, liver, or blood disorders. Historically used before PSA testing, PAP has largely been replaced by PSA for screening and monitoring. It’s rarely used today except in specific clinical situations alongside other tests and imaging.

Normal serum acid phosphatase is typically around 0–5 units per litre (U/L), though many laboratories use ranges roughly 0–3.5 U/L or up to 8 U/L depending on assay, sex and age. Prostatic (prostate-specific) acid phosphatase has its own reference range. Always interpret results against the reference interval provided by the testing laboratory and in clinical context.

Acid phosphatase in the liver is a lysosomal enzyme that hydrolyzes phosphate esters at acidic pH, releasing inorganic phosphate. It aids intracellular digestion and turnover of phosphorylated macromolecules, supports autophagy and lysosomal degradation, and helps recycle phosphate for metabolism. Proper activity maintains cellular homeostasis and clearance of damaged organelles; altered levels may indicate lysosomal dysfunction or liver pathology.