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Introduction ⬇

Acid phosphatases are enzymes that are widely distributed in tissues, including the bone, liver, spleen, kidney, RBCs, and platelets. However, their greatest diagnostic importance involves the prostate gland, where acid phosphatase activity is 100 times higher than in other tissues. Immunochemical methods are highly specific for determining the prostatic fraction; however, because prostatic acid phosphatase (PAP) is not elevated in early prostatic disease, this test is not recommended for screening.

This test monitors the effectiveness of treatment of cancer of the prostate. Elevated levels of acid phosphatase are seen when prostate cancer has metastasized beyond the capsule to the other parts of the body, especially the bone. Once the carcinoma has spread, the prostate starts to release acid phosphatase, resulting in an increased blood level. The prostatic fraction procedure specifically measures the concentration of PAP secreted by cells of the prostate gland. Acid phosphatase is also present in high concentration in seminal fluid. Tests for presence of this enzyme on vaginal swabs may be used to investigate sexual assault.

Normal Findings ⬆ ⬇

Total acid phosphatase:

PAP:

Procedure ⬆ ⬇

  1. Obtain a 5-mL venous blood sample. Serum may be used, if test is done within 1 hour. EDTA plasma is preferred to stabilize acid phosphatase.

  2. Obtaining a specimen in the morning is recommended because diurnal variation exists.

  3. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Place the specimen in a biohazard bag, transport to laboratory immediately, and place on ice.

Clinical Implications ⬆ ⬇

  1. A significantly elevated acid phosphatase value is almost always indicative of metastatic cancer of the prostate. If the tumor is successfully treated, this enzyme level will drop within 3–4 days after surgery or 3–4 weeks after estrogen administration.

  2. Moderately elevated values also occur in the absence of prostate carcinoma in the following conditions:

    1. Niemann–Pick disease (inherited metabolic disorder, a form of sphingolipidosis)

    2. Gaucher disease (a form of lysosomal storage disease)

    3. Prostatitis (benign prostatic hypertrophy [BPH]); benign prostatic hyperplasia

    4. Kidney disease

    5. Any cancer that has metastasized to the bone

    6. Myelocytic leukemia

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain test purpose and procedure.

  2. No palpation of or procedures on the prostate gland and no rectal examinations should be performed 2–3 days before test.

  3. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Have patient resume normal activities.

  2. Review test results; report and record findings. Modify the nursing care plan as needed. Counsel appropriately regarding repeat testing. When elevated values are present, retesting and biopsy are considered.

  3. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆

  1. Various drugs may cause increased or decreased PAP levels.

  2. Palpation of the prostate gland and prostate biopsy before testing cause increases in PAP levels.

  3. Transurethral resection of the prostate (TURP) and bladder catheterization cause increased levels.