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PROSTATE SPECIFIC ANTIGEN (PSA)

Item Value
Available Stat? No
Test code PSA
Performed by? Chemistry
Sendout? no
Price range $$$
In House Availability Monday - Friday
Principle The Siemens Centaur assay is a two-site sandwich immunoassay using direct chemiluminometric technology. The assay standardization is traceable to World Health Organization (WHO) International Standard (96/670).

Note: This assay measures both free and complexed PSA.
Interpretation The presence of PSA has been demonstrated in normal, benign, hyperplastic, and malignant prostatic tissue. PSA is not produced by cancers of the breast, lung, colon, rectum, stomach, pancreas, or thyroid. Elevated serum PSA has been reported in patients with prostate cancer, benign prostatic hypertrophy, and in inflammatory conditions of genitourinary tissue adjacent to the prostate. Persistent elevation of PSA following treatment or increase in a pretreatment PSA level is indicative of recurrent or residual disease.
Container type gold top gel tube
Amount to Collect 2 mL
Sample type Blood
Normal range < 4.0 mcg/L (ng/mL).
Synonyms PSA;
Stability Serum is stable at 2-8°C for 48 hours and at -20°C for 60 days.
Interferences 1. Auto- (rheumatoid factor) and heterophile antibodies in human serum can react with reagent immunoglobulins, interfering with in vitro immunoassays. Patients routinely exposed to animals or to animal serum products can be prone to this interference. Anomalous values may be observed. The most common, although not exclusive, interference seen in immunometric ("two-site," "sandwich") assays is a spuriously high value. Results inconsistent with clinical findings or previous laboratory values can be investigated by the laboratory for this phenomenon. Call the Clinical Chemistry Laboratory Medicine Resident (x65527, pager 415-443-2311).

2. A paradoxical, false low result may rarely occur when patient samples with extremely high concentrations of peptide/protein analytes (e.g. AFP, hCG, PSA, etc.) are measured by immunometric ("two-site," or "sandwich") assays. For example, a true value of 3,000,000 U/L could be reported as < 5 or 21 U/L. This phenomenon is called the "high dose hook effect." Results inconsistent with clinical findings or previous laboratory values can be investigated by the laboratory for this phenomenon. Call the Clinical Chemistry Laboratory Medicine Resident (x65527, pager 415-443-2311).

3. The concentration of PSA in a given specimen can vary due to differences in assay methods and reagent specificity. Values obtained with different assay methods cannot be used interchangeably.

4. Do not interpret PSA results as absolute evidence of the presence or absence of malignant disease. The obtained PSA value should be used in conjunction with information available from clinical evaluation and other diagnostic procedures.

It is possible that a patient with confirmed prostatic cancer may have serum PSA levels within the range of those observed in the healthy individual. Elevated PSA levels also can be found in patients with nonmalignant diseases of the prostrate along with other adjacent genitourinary tissues.
Hormonal therapy has been seen to affect PSA expression; therefore, low PSA measurement after this type of treatment may not adequately reflect the presence of residual or recurrent disease states.
Additional information Note: Not approved for screening.
References 1. Bayer 119746 Rev. E, 2001-08. Siemens Medical Solutions Diagnostics, Malvern, PA.

2. Henry, J.B., ed. Clinical Diagnosis and Management by Laboratory Methods. 20th edition, Philadelphia, W.B. Sanders, 2001, pp. 1032; 1040-1041.

3. Armbruster, D.A.: Prostate-specific antigen: Biochemistry, analytical methods, and clinical application. Clin Chem 39(2):181-195, 1993.

4. Stamey, T.A., Kabalin, J.N., et al.: Prostate specific antigen in the diagnosis and treatment of adenocarcinoma of the prostate. J Urol 141:1070-1090, 1989.
CPT coding 84153
Last Updated 6/18/2011 8:13:25 AM
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