Test Catalog

Test ID: PACP    
Prostatic Acid Phosphatase, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Aiding in predicting recurrence after radical prostatectomy for clinically localized prostate cancer


Following response to androgen ablation therapy, when used in conjunction with prostate-specific antigen

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Prostatic acid phosphatase (PAP), a glycoprotein synthesized by the prostate gland, is a member of a diverse group of isoenzymes that are capable of hydrolyzing phosphate esters in acidic medium. They are classified on the basis of their electrophoretic mobilities.


PAP was a major tumor marker for prostate cancer for more than 50 years.(1) However, PAP is no longer used to screen for or stage prostate cancer. In most instances, serum prostate specific antigen (PSA) is used instead. PAP usefulness is now limited to niche applications. Pre-treatment PAP measurement may add unique, clinically useful prognostic information for predicting recurrence in men who are undergoing radical prostatectomy for clinically localized prostate cancer. PAP also may be useful for following the progression of disease response to therapy in men treated by androgen ablation. However, for both of these applications, PSA provides more information and also should be utilized.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

< or =2.1 ng/mL

Interpretation Provides information to assist in interpretation of the test results

Prostatic acid phosphatase (PAP) levels above the reference range may indicate prostate cancer, but can be due to many other factors, see Cautions.


A rise in PAP levels in patients with known prostate cancer can indicate tumor progression or recurrence. However, there is considerable intra-subject biological variability, limiting the usefulness of this test.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Prostatic acid phosphatase (PAP) measurement must not be regarded as an absolute test for malignancy since other factors, including benign prostatic hyperplasia, prostatic infarction, and manipulation of the prostate gland may result in elevated serum PAP concentrations.


PAP measurements provide little additional information beyond that provided by prostate-specific antigen measurements.


Human anti-mouse antibodies (HAMA) may be present in specimens from patients who have received immunotherapy utilizing monoclonal antibodies. Other heterophile antibodies also may be present in patient specimens. This assay has been specifically formulated to minimize the effects of these antibodies on the assay. However, carefully evaluate results from patients known to have such antibodies.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Moul JW, Connelly RR, Perahia B, McLeod DG: The contemporary value of pretreatment prostatic acid phosphatase to predict pathological stage and recurrence in radical prostatectomy cases. J Urol. 1998;159:935-940

2. Beaver TR, Schultz AL, Fink LM, et al: Discordance between concentration of prostate-specific antigen and acid phosphatase in serum of patients with adenocarcinoma of the prostate. Clin Chem. 1988;34:1524

3. Velonas VM, Woo HH, dos Remedios CG, Assinder SJ: Current status of biomarkers for prostate cancer. Int J Mol Sci. 2013 May 24;14(6):11034-60. doi: 10.3390/ijms140611034

4. Kong HY, Byun J: Emerging roles of human prostatic Acid phosphatase. Biomol Ther (Seoul). 2013 Jan;21(1):10-20. doi: 10.4062/biomolther.2012.095