Prostatic acid phosphatase (PAP)

Alternative names 
Prostatic acid phosphatase test; Serum acid phosphatase; Male PAP test

The PAP test is a blood test that measures prostatic acid phosphatase (an enzyme found primarily in men in the prostate gland and semen) to determine the health of the prostate gland. Prostate dysfunction results in the release of PAP into the blood.

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band or blood pressure cuff is placed around the upper arm. This causes veins below the band to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

How to prepare for the test
This test usually does not require special preparation. As with any blood test, the health care provider may limit certain foods or medications shortly before the test to assure an accurate sample.

Drugs that can interfere with PAP measurements include fluorides, oxalates, clofibrate, and alcohol

How the test will feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing in the area.

Why the test is performed
This test is most often performed to determine whether you have Prostate cancer, an abnormality of the prostate gland, or to follow the response of Prostate cancer to treatment.

This test is no longer used routinely. The availability of the more sensitive and specific PSA assay has largely replaced the PAP test’s clinical use.

Normal Values

Normal Values
vary from laboratory to laboratory. Please contact your laboratory or consult your health care provider for normal values.

What abnormal results mean

Abnormal PAP values can be obtained for many reasons. The most common reasons for abnormal PAP values include, but are not limited to:

  • Prostate cancer  
  • Prostate cancer that has spread outside the prostate (particularly to bone)  
  • Decreased blood flow to prostate  
  • Paget’s disease (bones become thicker and softer)  
  • Anemia  
  • Infection (usually severe)  
  • Thrombophlebitis  
  • Gaucher’s disease  
  • Hyperparathyroidism  
  • Heart attack  
  • kidney disease  
  • Physical stimulation of the prostate (colonoscopy, enemas, prostate examination)  
  • Multiple Myeloma  
  • Prostatitis

What the risks are

  • Excessive bleeding  
  • Fainting or feeling lightheaded  
  • Hematoma (blood accumulating under the skin)  
  • Infection (a slight risk any time the skin is broken)  
  • Multiple punctures to locate veins

Special considerations

Prostate cancer that is located only in the prostate gland may not produce high enough levels to indicate a problem. If your PAP test is normal it does not eliminate the possibility that you have Prostate cancer.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Johns Hopkins patient information

Last revised: December 7, 2012
by Mamikon Bozoyan, M.D.

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.