acid phosphatase in serum

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Reference interval

  • Male & Female: 0.3 - 0.7 U/L


The intended use of the Kodak Ektachem Clinical Chemistry Slide (AcP) is to quantitatively measure acid phosphatase activity of prostatic origin in serum or plasma.

The Kodak Ektachem Clinical Chemistry Slide (AcP) is a dry, multilayered, self-contained analytical element coated on a transparent polyester support. It is a TWO-POINT RATE test (color density is read at two fixed times during incubation).

A 10uL drop of sample is deposited on the slide & is evenly distributed by the spreading layer. Acid phosphatase in the sample hydrolyzes a-naphthyl phosphate to form a-naphthol at pH 5.5. 1,5-Pentanediol & 1,4-butanediol serve as phosphate acceptors to preferentially activate the prostatic acid phosphatase fraction. The a-naphthol couples to the diazo dye 4-chloro-2-methylbenzenediazonium salt (Fast RED TR salt) to form an azo dye. The rate of dye formation is proportional to the amount of acid phosphatase present in the sample. The sample is incubated at 37 C & the reflectance density measured at 2.25 & 5 minutes. The reaction rate is calculated as the difference in density between these two read times & is converted to enzyme activity. Reflectance density is measured at 600 nm to minimize interference due to bilirubin.

Since this method is standardized to a thymolphthalein monophosphate (TMP) substrate-based method & utilizes conditions which favor measurement of the prostatic isoenzyme of acid phosphatase, results are substantially equivalent to a TMP-based assay. Additionally, the Kodak method correlates well with a commercially available method which utilizes TMP as substrate.

Clinical significance

Prostatic acid phosphatase measurement must not be regarded as an absolute test for malignancy, since other factors including benign prostatic hyperplasia, prostatic infarction & manipulation of the prostate gland may result in elevated serum acid phosphatase activity. Acid phosphatase activity is not increased in all patients with prostate cancer. Accordingly, prostatic acid phosphatase results should always be interpreted in light of the patient's clinical history & the results of other diagnostic procedures. The concentration/activity of prostatic acid phosphatase in a given specimen determined with assays from different manufacturers can vary due to differences in assay methods & reagent specificity. The results reported by the laboratory to the physician must include the identity of the prostatic acid phosphatase assay used. Values obtained with different prostatic acid phosphatase assays cannot be used interchangeably. Before changing assays, the laboratory must confirm baseline values for patients being serially monitored.




Patient preparation: No special patient preparation is required.

For serum preparation: Collect the specimen by standard venipuncture technique. Specimen should not be collected immediately after gastrointestinal procedures or prostate manipulation.

Patient specimens should be kept on ice immediately after collection & the serum/plasma must be acidified as soon as possible to maintain acid phosphatase stability & prevent matrix bias. To prepare acidified samples, remove the serum/plasma promptly from the clot or cells & add 50 uL Kodak Ektachem Citric Acid Solution per mL of serum/plasma to be treated & mix the acidified sample for 5-10 seconds (200 uL of patient/10 uL of Citric acid).

Minimum sample size of 0.5 milliliter: with an optimum size of 1.0 mL or larger.

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  1. Tietz NW, Textbook of Clinical Chemistry, W.B. Saunders, Philadelphia, 1986 p. 752-754.
  2. Tietz, N., Fundamental of Clinical Chemistry, 3rd Edition, W. B. Saunders Company, Philadelphia, 1987, p. 408-409.
  3. Kodak Ektachem 700 Analyzer Operator's Manual, Kodak Ektachem Clinical Product, Eastman Kodak Company, Rochester, New York.
  4. Package Insert, Kodak Ektachem Clinical Chemistry Acid Phosphatase Slide, Kodak Clinical Product, Eastman Kodak Company, Rochester, New York.
  5. 5.0 5.1 Interpretation of Diagnostic tests, 8th edition, Wallach J, Lippincott, Williams & Wilkens, Philadelphia, 2007