PSA

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Também chamado: Total PSA; Free PSA; Complexed PSA
Nome formal: Prostate Specific Antigen

De relance

Por que fazer este exame?

To screen asymptomatic and symptomatic men for prostate cancer, to help determine the necessity for a biopsy of the prostate, to monitor the effectiveness of treatment for prostate cancer, and to detect recurrence of prostate cancer; there is currently no consensus about using PSA tests to screen for prostate cancer.

Quando fazer este exame?

When a man has symptoms suggestive of prostate cancer such as difficult, painful, and/or frequent urination; may also be ordered during and at regular intervals after prostate cancer treatment. There is continued debate among experts and national organizations over when and how often to order the PSA test to screen asymptomatic men. The frequency of prostate cancer screening is an individual decision that should be determined through discussion with your physician. (For specific details, see prostate cancer screening for adults and adults 50 and up).

Amostra:

A blood sample drawn from a vein in the arm

É necessária alguma preparação?

None, but keep in mind that the sample should be collected prior to your doctor performing a digital rectal exam (DRE) and prior to (or several weeks after) a prostate biopsy.

A amostra

O que está sendo pesquisado?

PSA is a protein produced primarily by cells in the prostate, a small gland that encircles the urethra in males and produces a fluid that makes up part of semen. Most of the PSA that the prostate produces is released into this fluid, but small amounts of it are also released into the bloodstream. PSA exists in two forms in the blood: free (not bound) and complexed (cPSA, bound to a protein). The most frequently used PSA test is the total PSA, which measures the sum of the free PSA and the cPSA in the blood. When a doctor orders a “PSA test,” he is referring to a total PSA.

This test is used as a tumor marker to screen for and to monitor prostate cancer. It is a good tool but not a perfect one, and currently there is no consensus among experts on the usefulness of this test for screening asymptomatic men. Elevated levels of PSA are associated with prostate cancer, but they may also be seen with prostatitis and benign prostatic hyperplasia (BPH). Mild to moderately increased concentrations of PSA may be seen in those of African American heritage, and levels tend to increase in all men as they age.

PSA is not diagnostic of cancer. The gold standard for identifying prostate cancer is the prostate biopsy, collecting small samples of prostate tissue and identifying abnormal cells under the microscope. The total PSA test and digital rectal exam (DRE) are used together to help determine the need for a prostate biopsy. The goal of screening is to minimize unnecessary biopsies and to detect clinically significant prostate cancer while it is still confined to the prostate. The term clinically significant is important because while prostate cancer becomes relatively common in men as they age, many of the tumors are very slow-growing and this type of cancer is an uncommon cause of death. Doctors must try to both detect prostate cancer and to differentiate between slow-growing cases and prostate cancers that may grow aggressively and spread to other parts of the body (metastasize). Over-diagnosing and over-treatment are issues with which doctors are currently grappling. In some cases, the treatment can be worse than the cancer, with the potential for causing significant side effects, incontinence, and erectile dysfunction. The PSA test and DRE can detect most cases of prostate cancer, but they cannot, in general, predict the course of a person’s disease.

Free PSA and cPSA tests can be ordered individually. The tests that measure them were developed to better differentiate between cancer-related and non-cancer-related PSA increases. Both of the tests operate on the principle that men with prostate cancer frequently have altered ratios of the two forms of PSA - decreased amounts of free PSA and increased amounts of cPSA.

Como a amostra é obtida para o exame?

A blood sample is taken by needle from a vein in the arm.

NOTA: Se exames médicos em você ou em alguém importante para você o deixam ansioso ou constrangido, ou se você tem dificuldade de lidar com eles, leia um ou mais dos seguintes artigos: Lidando com dor, desconforto ou ansiedade durante o exame, Conselhos sobre exames de sangue, Conselhos para ajudar crianças durante exames médicos, and Conselhos para ajudar idosos durante exames médicos.

Outro artigo, Siga essa amostra, fornece uma visão da coleta e do processamento de uma amostra de sangue e de uma amostra de cultura da garganta.

É necessário algum preparo para garantir a qualidade da amostra?

The sample should be collected prior to the physician performing a digital rectal exam (DRE) and prior to (or several weeks after) a prostate biopsy.

O exame

Perguntas frequentes

Pergunte ao laboratório

* indica um campo necessário



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Fontes do artigo

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NOTA: Este artigo se baseia em pesquisas que incluíram as fontes citadas e a experiência coletiva de Lab Tests Online Conselho de Revisão Editorial. Este artigo é submetido a revisões periódicas do Conselho Editorial, e pode ser atualizado como resultado dessas revisões. Novas fontes citadas serão adicionadas à lista e distinguidas das fontes originais usadas.

Sources Used in Current Review

Pagana, K. D. & Pagana, T. J. (© 2007). Mosby’s Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 772-774.

Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pp 243, 246.

Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 906-913.

(2008 November 20). What you need to know about Prostate Cancer. National Cancer Institute [On-line information]. Available online at http://www.cancer.gov/cancertopics/wyntk/prostate through http://www.cancer.gov. Accessed March 2009.

(© 2009). Detailed Guide: Prostate Cancer. American Cancer Society [On-line information]. Available online at http://www.cancer.org/docroot/CRI/CRI_2_3x.asp?rnav=cridg&dt=36 through http://www.cancer.org. Accessed March 2009.

(2009 March 19). PSA Testing: What Should Men Do? Fallout from 2 studies, pro and con, has experts in a quandary. MedlinePlus HealthDay [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/news/fullstory_81937.html through http://www.nlm.nih.gov. Accessed March 2009.

Morse Linn, M. et al (Posted 2008 January 9). Prostate-Specific Antigen Screening: Friend or Foe? Emedicine from Urol Nurs. 2007;27(6):481-489. [On-line information]. Available online at http://www.medscape.com/viewarticle/568053 through http://www.medscape.com. Accessed March 2009.

Chustecka, Z. News and Lie, D. CME (Released 2008 August 5). USPSTF Recommends Against Prostate Cancer Screening in Men 75 Years or Older. CME/CE Medscape Medical News, Online CME [On-line information]. Available online at http://www.medscape.com/viewarticle/578591 through http://www.medscape.com. Accessed March 2009.

Michael, A. et al (Posted 2009 March 6). Prostate Cancer Chemotherapy in the Era of Targeted Therapy. Medscape from Prostate Cancer Prostatic Dis. 2009;12(1):13-16. [On-line information]. Available online at http://www.medscape.com/viewarticle/589071 through http://www.medscape.com. Accessed March 2009.

Melanie Ketchandji, M. et al (Posted 2009 February 5). Cause of Death in Older Men After the Diagnosis of Prostate Cancer. Medscape from J Am Geriatr Soc. 2009;57(1):24-30. Available online at http://www.medscape.com/viewarticle/586741 through http://www.medscape.com. Accessed March 2009.

(Reviewed 2009 March 18). Prostate-Specific Antigen (PSA) Test. NCI Fact Sheet [On-line information]. Available online at http://www.cancer.gov/cancertopics/factsheet/Detection/PSA through http://www.cancer.gov. Accessed March 2009.

Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER and Bruns DE, eds. 4th ed. St. Louis, Missouri: Elsevier Saunders; 2006, Pg 761.

(July 30, 2009) American Cancer Society. Following PSA Levels After Treatment Meant to Cure Prostate Cancer. Available online at http://www.cancer.org/docroot/CRI/content/CRI_2_4_4X_Following_PSA_levels_36.asp?sitearea= through http://www.cancer.org. Accessed August 2009.

McDermed J. Using PSA Intelligently to Manage Prostate Cancer. Part 2 of 2. PCRI Insights. August, 2005. Vol. 8, no. 3. Available online at http://www.prostate-cancer.org/education/preclin/McDermed_Using_PSA_Intelligently2.html through http://www.prostate-cancer.org. Accessed November 2009.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber’s Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby’s Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

Ballentine Carter, H., et. al. (2204 September 22). Report to the Nation on Prostate Cancer 2004, Chapter 1: Detection, Diagnosis, and Prognosis of Prostate Cancer CME. Medscape Today, Clinical Update [On-line CME]. Available online at http://www.medscape.com/viewprogram/3440?src=sidesearch through http://www.medscape.com.

(2005 January 1, Revised). Detailed Guide: Prostate Cancer, Can Prostate Cancer Be Found Early? American Cancer Society [On-line information]. Available online through http://www.cancer.org.

(2004 August 17, Reviewed). The Prostate-Specific Antigen (PSA) Test: Questions and Answers. National Cancer Institute, Cancer Facts [On-line information]. Available online at http://cis.nci.nih.gov/fact/5_29.htm through http://cis.nci.nih.gov.

(2004 May 26). Some Men with Low PSAs Have Prostate Cancer: Most Cancers Found Are Not Likely to Be Clinically Significant. NIH News [On-line Press Release]. Available online at http://www.nih.gov/news/pr/may2004/nci-26.htm through http://www.nih.gov.

(© 1995 – 2004). Benign Prostatic Hyperplasia. Merck Manual [On-line information]. Available online through http://www.merck.com.

(2003 March, Reviewed). Benign Prostatic Hyperplasia (BPH). Familydoctor.org [[On-line information]. Available online at http://familydoctor.org/148.xml through http://familydoctor.org.

(2003 August, Reviewed). American Urological Association. Benign Prostatic Hyperplasia (BPH), A Patient’s Guide. Available online through http://www.urologyhealth.org.