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Encyclopedia > Prostate specific antigen
kallikrein-related peptidase 3
Identifiers
Symbol KLK3
Alt. Symbols APS
Entrez 354
HUGO 6364
OMIM 176820
RefSeq NM_145864
UniProt P07288
Other data
Locus Chr. 19 q13.41

Prostate specific antigen (PSA) is a protein produced by the cells of the prostate gland. PSA is present in small quantities in the serum of normal men, and is often elevated in the presence of prostate cancer and in other prostate disorders. A blood test to measure PSA is the most effective test currently available for the early detection of prostate cancer. Higher than normal levels of PSA are associated with both localized and metastatic prostate cancer (CaP). The Entrez logo The Entrez Global Query Cross-Database Search System allows access to databases at the National Center for Biotechnology Information (NCBI) website. ... Hugo is a masculine name. ... The Mendelian Inheritance in Man project is a database that catalogues all the known diseases with a genetic component, and - when possible - links them to the relevant genes in the human genome. ... The National Center for Biotechnology Information (NCBI) is part of the US National Library of Medicine (NLM), which is a branch of the US National Institutes of Health. ... Swiss-Prot is a curated biological database of protein sequences created in 1986 by Amos Bairoch during his PhD and developed by the Swiss Institute of Bioinformatics and the European Bioinformatics Institute. ... Short and long arms Chromosome. ... Chromosome 19 is one of the 23 pairs of chromosomes in humans. ... The prostate is a compound tubuloalveolar exocrine gland of the male mammalian reproductive system. ... Blood plasma is the liquid component of blood, in which the blood cells are suspended. ... Prostate cancer is a disease in which cancer develops in the prostate, a gland in the male reproductive system. ... Metastasis (Greek: change of the state) is the spread of cancer from its primary site to other places in the body. ...

Contents

Biochemistry

Prostate specific antigen (PSA), also known as kallikrein III, seminin, semenogelase, γ-seminoprotein and P-30 antigen) is a glycoprotein manufactured almost exclusively by the prostate gland; PSA is produced for the ejaculate where it liquifies the semen and allows sperm to swim freely.[1] It is also believed to be instrumental in dissolving the cervical mucous cap, allowing the entry of sperm.[2] A glycoprotein is a macromolecule composed of a protein and a carbohydrate (an oligosaccharide). ... Male Anatomy The prostate is a gland that is part of male mammalian sex organs. ... Semen or ejaculate is the fluid discharged from the penis during ejaculation, usually at the time of orgasm. ... Horse semen being collected for breeding purposes. ... A spermatozoon or spermatozoan ( spermatozoa), from the ancient Greek σπέρμα (seed) and (living being) and more commonly known as a sperm cell, is the haploid cell that is the male gamete. ...


Biochemically it is a serine protease (EC 3.4.21.77) enzyme, the gene of which is located on the nineteenth chromosome (19q13). [3] Crystal structure of Trypsin, a typical serine protease. ... The Enzyme Commission number (EC number) is a numerical classification scheme for enzymes, based on the chemical reactions they catalyze. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... For a non-technical introduction to the topic, see Introduction to Genetics. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ...


Clinical significance

Risk of prostate cancer in two age groups based on Free PSA as % of Total PSA [4]

PSA is normally present in the blood at very low levels; normal PSA levels are defined as between 0-4.0 mg per milliliter.[5] Increased levels of PSA may suggest the presence of prostate cancer. However, prostate cancer can also be present in the complete absence of an elevated PSA level, in which case the test result would be a false negative.[6] PSA levels can be also elevated due to prostate infection, irritation, benign prostatic hypertrophy (enlargement) or hyperplasia (BPH) or recent ejaculation[7], in which case it may give a false positive. [8] It is a myth that digital rectal exam raises PSA. [9] Image File history File links Size of this preview: 644 × 600 pixels Full resolution (1127 × 1050 pixel, file size: 15 KB, MIME type: image/png) I created this graph from data in JAMA. 1998;279:1542-1547 Ryanjo 00:12, 18 September 2006 (UTC) I, the creator of this work... Image File history File links Size of this preview: 644 × 600 pixels Full resolution (1127 × 1050 pixel, file size: 15 KB, MIME type: image/png) I created this graph from data in JAMA. 1998;279:1542-1547 Ryanjo 00:12, 18 September 2006 (UTC) I, the creator of this work... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... In statistics, a false negative, also called a Type II error or miss, exists when a test incorrectly reports that a result was not detected, when it was really present. ... Benign prostatic hyperplasia (BPH) is the increase in size of the prostate in middle_aged and elderly men. ... A false positive, also called false alarm, exists when a test reports, incorrectly, that it has found a signal where none exists in reality. ... A rectal examination or rectal exam is an internal examination of the rectum by a physician. ...


Despite earlier findings,[10] recent research suggests that the rate of increase of PSA (the PSA velocity) is not a more specific marker for prostate cancer.[11] However, the PSA rate of rise may have value in prostate cancer prognosis. Men with prostate cancer whose PSA level increased by more than 2.0 ng per milliliter during the year before the diagnosis of prostate cancer have a higher risk of death from prostate cancer despite undergoing radical prostatectomy.[12] Radical retropubic prostatectomy is a surgical procedure in which the prostate gland is removed through an incision in the abdomen. ...


Most PSA in the blood is bound to serum proteins. A small amount is not protein bound and is called free PSA. In men with prostate cancer the ratio of free (unbound) PSA to total PSA is decreased. The risk of cancer increases if the free to total ratio is less than 25%. (See graph at right.) The lower the ratio the greater the probability of prostate cancer. Measuring the ratio of free to total PSA appears to be particularly promising for eliminating unnecessary biopsies in men with PSA levels between 4 and 10 ng/mL.[13] However, both total and free PSA increase immediately after ejaculation, returning slowly to baseline levels within 24 hours.[7] Brain biopsy A biopsy (in Greek: bios = life and opsy = look/appearance) is a medical test involving the removal of cells or tissues for examination. ...


Prostate cancer screening

The U.S. Food and Drug Administration (FDA) has approved the PSA test for annual screening of prostate cancer in men of age 50 and older. PSA levels between 4 and 10 ng/mL (nanograms per milliliter) are considered to be suspicious and should be followed by rectal ultrasound imaging and, if indicated, prostate biopsy. PSA is false positive-prone (7 out of 10 men in this category will still not have prostate cancer) and false negative-prone (2.5 out of 10 men with prostate cancer have no elevation in PSA).[14] Recent reports indicate that refraining from ejaculation 24 hours or more prior to testing will improve test accuracy.[7] The United States Food and Drug Administration is the government agency responsible for regulating food, dietary supplements, drugs, cosmetics, medical devices, biologics and blood products in the United States. ... Medical ultrasonography (sonography) is an ultrasound-based diagnostic imaging technique used to visualize muscles and internal organs, their size, structures and possible pathologies or lesions. ... Prostate biopsy is a procedure in which small samples are removed from a mans prostate gland to be tested for the presence of cancer. ...


The current guidelines of the American Cancer Society (ACS) recommend that men over age 50 should be offered the digital rectal exam and PSA tests yearly,[15] but does not currently recommend routine screening.[16] Rather, the ACS recommends that individual men discuss the potential benefits and risks of testing with their doctors in order to make an informed decision on whether or not to be tested. Screening should be offered annually to African-American men and those with a family history of prostate cancer upon reaching 45 years. Other racial and ethnic groups, such as Asian- and Hispanic-Americans have a lower risk of prostate cancer, and may not benefit from screening. Screening is likely not useful for men over age 70 or with other significant medical problems and a life expectancy of fewer than 10 years. The U.S. Preventive Services Task Force (USPSTF) concluded that "the evidence is insufficient to recommend for or against routine screening for prostate cancer using prostate specific antigen (PSA) testing".[17] However, PSA screening is common even among older men for whom benefit is least clear.[18] 2006 is a common year starting on Sunday of the Gregorian calendar. ... The American Cancer Society (ACS) is a medical organization with a corporate attitude in the United States. ... A rectal examination or rectal exam is an internal examination of the rectum by a physician. ... Evidence-based medicine (EBM) is an attempt to more uniformly apply the standards of evidence gained from the scientific method, to certain aspects of medical practice. ...


These guidelines may be changing. A new European study has shown that a thorough screening for prostate cancer every 4 years is adequate. The screening comprises a PSA blood test, a digital rectal exam, and a transrectal ultrasound. "Very few, if any, aggressive prostate cancers escape (this) screening."[19]


See also

Type I errors (or α error, or false positive) and type II errors (β error, or a false negative) are two terms used to describe statistical errors. ... Prostate cancer is a disease in which cancer develops in the prostate, a gland in the male reproductive system. ... Prostate cancer screening is an attempt to identify individuals with prostate cancer in a broad segment of the population—those for whom there is no reason to suspect prostate cancer. ... Tumor markers are substances found in the blood, urine or body tissues that can be elevated in cancer. ...

Footnotes

  1. ^ Steven P. Balk, Yoo-Joung Ko, Glenn J. Bubley (2003). "Biology of Prostate-Specific Antigen" (Abstract). Journal of Clinical Oncology 28 (2): 383-91. Retrieved on 2006-09-17. 
  2. ^ "Chapter 8: What is the prostate and what is its function?", American Society of Andrology Handbook. 
  3. ^ Lilja H. (Nov 2003). "Biology of Prostate-Specific Antigen". Urology 62 ((5 Suppl 1)): 27-33. PMID 14607215. Retrieved on 2006-09-17. 
  4. ^ Catalona W, Partin A, Slawin K, Brawer M, Flanigan R, Patel A, Richie J, deKernion J, Walsh P, Scardino P, Lange P, Subong E, Parson R, Gasior G, Loveland K, Southwick P (1998). "Use of the percentage of free prostate-specific antigen to enhance differentiation of prostate cancer from benign prostatic disease: a prospective multicenter clinical trial.". JAMA 279 (19): 1542-7. PMID 9605898. 
  5. ^ Myrtle JF. (1989). "Normal levels of prostate-specific antigen (PSA)", in Edited by WJ Catalona, DS Coffey, JP Karr: Clinical aspects of prostate cancer: assessment of new diagnostic and management procedures. New York: Elsevier, 183–9. 
  6. ^ Thompson I, Pauler D, Goodman P, Tangen C, Lucia M, Parnes H, Minasian L, Ford L, Lippman S, Crawford E, Crowley J, Coltman C (2004). "Prevalence of prostate cancer among men with a prostate-specific antigen level < or =4.0 ng per milliliter.". N Engl J Med 350 (22): 2239-46. PMID 15163773. 
  7. ^ a b c Herschman JD, Smith DS, Catalona WJ (1997), "Effect of ejaculation on serum total and free prostate-specific antigen concentrations", Urology 50 (2): 239-43
  8. ^ American Cancer Society (26 July 2006). Can Prostate Cancer Be Found Early?. Detailed Guide: Prostate Cancer. Retrieved on 2006-09-14.
  9. ^ Kumar and Clark, Sixth Edition, Elsevier Saunders, 2005, p. 685.
  10. ^ {Carter H, Pearson J, Metter E, Brant L, Chan D, Andres R, Fozard J, Walsh P (1992). "Longitudinal evaluation of prostate-specific antigen levels in men with and without prostate disease.". JAMA 267 (16): 2215-20. PMID 1372942. 
  11. ^ H. Ballentine Carter (2006). "Assessing Risk: Does This Patient Have Prostate Cancer?" (Editorial). Journal of the National Cancer Institute 98 (8): 506-7. Retrieved on 2006-09-14. 
  12. ^ D'Amico A, Chen M, Roehl K, Catalona W (2004). "Preoperative PSA velocity and the risk of death from prostate cancer after radical prostatectomy.". N Engl J Med 351 (2): 125-35. PMID 15247353. 
  13. ^ Catalona W, Smith D, Ornstein D (1997). "Prostate cancer detection in men with serum PSA concentrations of 2.6 to 4.0 ng/mL and benign prostate examination. Enhancement of specificity with free PSA measurements.". JAMA 277 (18): 1452-5. PMID 9145717. 
  14. ^ Thompson I, Pauler D, Goodman P, Tangen C, Lucia M, Parnes H, Minasian L, Ford L, Lippman S, Crawford E, Crowley J, Coltman C (2004). "Prevalence of prostate cancer among men with a prostate-specific antigen level < or =4.0 ng per milliliter.". N Engl J Med 350 (22): 2239-46. PMID 15163773. 
  15. ^ National Guideline Clearinghouse. Recommendations from the American Cancer Society Workshop on Early Prostate Cancer Detection. Retrieved on 2006-09-14.
  16. ^ American Cancer Society. What the American Cancer Society Recommends. Retrieved on 2007-01-16.
  17. ^ U.S. Preventive Services Task Force (December 2002)). Screening for Prostate Cancer. Retrieved on 2006-09-14.
  18. ^ Scales C, Curtis L, Norris R, Schulman K, Albala D, Moul J (2006). "Prostate specific antigen testing in men older than 75 years in the United States.". J Urol 176 (2): 511-4. PMID 16813879. 
  19. ^ Schröder F, Raaijmakers R, Postma R, van der Kwast T, Roobol M (2005). "4-year prostate specific antigen progression and diagnosis of prostate cancer in the European Randomized Study of Screening for Prostate Cancer, section Rotterdam.". J Urol 174 (2): 489-94; discussion 493-4. PMID 16006878. 

For the Manfred Mann album, see 2006 (album). ... September 17 is the 260th day of the year (261st in leap years). ... For the Manfred Mann album, see 2006 (album). ... September 17 is the 260th day of the year (261st in leap years). ... For the Manfred Mann album, see 2006 (album). ... September 14 is the 257th day of the year (258th in leap years) in the Gregorian calendar. ... For the Manfred Mann album, see 2006 (album). ... September 14 is the 257th day of the year (258th in leap years) in the Gregorian calendar. ... For the Manfred Mann album, see 2006 (album). ... September 14 is the 257th day of the year (258th in leap years) in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... January 16 is the 16th day of the year in the Gregorian calendar. ... For the Manfred Mann album, see 2006 (album). ... September 14 is the 257th day of the year (258th in leap years) in the Gregorian calendar. ...

External links


  Results from FactBites:
 
The Prostate Centre | Prostate Specific Antigen (PSA) (195 words)
Prostate specific antigen (PSA) is an enzyme produced in the ducts of the prostate and absorbed into the bloodstream.
The PSA level that is considered normal for an average man ranges from 0 to 4 nanograms per milliliter (ng/ml).
A PSA level of 4 to 10 ng/ml is considered slightly elevated; levels between 10 and 20 ng/ml are considered moderately elevated; and anything greater is considered highly elevated.
  More results at FactBites »

 
 

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