Prostate specific antigen (PSA)

Red or tiger top tube
5-7 mL of venous blood

Additional information

Either draw specimen before or 1 week after digital prostate examination, any other prostatic manipulation, or even transrectal ultrasound (TRUS)
Test done at least 6 weeks after prostate biopsy
Handle sample gently to prevent hemolysis
Record patient’s age in the lab requisition form
Immediately put sample on ice and send it to lab

Prostate Specific Antigen (PSA) is:

A measure of the concentration of PSA in the blood
A serine glycoprotein synthesized by the epithelial cells of the prostate, periurethral, and perirectal glands
Produced for the ejaculate, where it aids in the liquefaction of semen
A test that can be used to effectively detect prostate cancer in its early stages

The clinical utility of PSA includes:

Screening for prostate cancer (along with digital rectal examination) that can effectively detect prostate cancer in its early stages
The USPSTF guidelines remain equivocal on whether the PSA test should be used for screening; however, the age group most likely to benefit are men ages 50-70 years or those at higher risk (+family history or African American) at age 45 years.
The USPSTF indicates that PSA testing not be performed in older men life expectancy <10 years
If prostate cancer screening using the PSA is performed; performing this once every 2 years is the recommended regimen (USPSTF)
The PSA level considered abnormal is related to age of the patient, with the cutoff level of 4 ng/mL typically results in 10-20% of prostate cancers being missed; but the number of false positives being minimized.
For evaluation of prostatic hypertrophy
Pretreatment PSA level useful as a prognostic tool predicting the capsular penetration, cancer volumes, and Gleason's scores
To monitor course of prostate cancer and recurrence
To evaluate the effectiveness of therapy for prostate cancer with antineoplastic drugs, and long term follow up
To stage prostate cancer

PSA is not a definitive diagnostic marker for prostatic carcinoma, as it may also be elevated in men with benign prostatic hypertrophy or prostatitis
PSA does not have the sensitivity or specificity to be considered an ideal tumor marker
PSA along with prostate acid phosphatase (PAP) increases the chance to detect prostate cancer in early stages
For the early detection of prostate cancer, the American Cancer Society and the American Urological Association have recommended (See the more conservative USPSTF recommendations above):

Men 50-75 years of age undergo annual measurement of serum PSA
Digital rectal examination (DRE)
Men at high risk, such as African Americans and men with strong family history, undergo annual screening beginning at age 40

PSA screening accuracy for detection of prostate cancer can also be improved by:

Use of age and race based reference ranges, which pertain to four major factors:

Prostatic enlargement
Inflammation
Presence of microscopic, but clinically insignificant cancer
Leakage of PSA into the serum

PSA velocity

Measurement of rate of PSA-change over time
Predicts clinical aggressiveness and behavior of prostate cancer

PSA density (PSA index)

Attempts to adjust for the contribution of prostatic hyperplasia (BPH) to the total serum PSA
Calculated by dividing the serum PSA by the volume of the prostate determined by ultrasound or other imaging techniques
Values >0.15 are suggestive of prostatic cancer
Useful only in individuals with PSA values between 4-9.99 ng/mL

Free to complexed PSA ratio

Cut-off values vary between studies, but values less than 15-27% are suggestive of prostatic carcinoma

Anti-PSA may be used as an immunohistochemical stain on tissue sections to affirm a prostatic origin of metastatic disease

Additional information

PSA half-life in serum is 2-3 days
Normal day to day variation is about 15-20%
Interfering factors

After prostate palpation or rectal exam (transient increase)
Increased with urinary retention or with recent catheterization or cystoscopy
Recent exposure to radioisotopes
Recent sexual activity (ejaculation)
High doses of chemotherapeutic drugs may cause possible increase or decrease:

Cyclophosphamide
Diethylstilbestrol
Methotrexate

Related laboratory tests include:

Biopsy of the prostate
Prostatic acid phosphatase (PAP)
Urine culture

Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.

	Conv. Units (ng/mL)	SI Units (µg/L)
Adult Males	<4.0	<4.0
Females	<0.5	<0.5
Age specific (Males)
40–49 yrs	<2.5	<2.5
50–59 yrs	<3.5	<3.5
60–69 yrs	<4.5	<4.5
70–79 yrs	<6.5	<6.5

Critical Alert

Normal PSA levels in patients with prostatic carcinoma can be attributed to:

Adenoid cystic-like carcinoma
Finasteride therapy
Low testosterone levels
Small-cell carcinoma
Undifferentiated carcinoma

Conditions associated with elevated PSA levels include:

Carcinoma of the prostate
Benign prostatic hyperplasia
Prostatitis
Prostatic biopsy and therapy
Prostatic infarct
Ejaculation (controversial)
Prostatic massage
Indwelling catheter
Exercise with trauma to area (bicycle)
Non-prostatic conditions

Breast or renal cell carcinoma
Hepatitis A
Parotid disorders

Others

Urinary retention
Infection
Biopsy

Drug induced

Testosterone

N/A

Drugs that decrease the PSA levels include:

Alpha-reductase inhibitor
Buserelin
Finasteride
Flutamide
GnRH analogs

Carter HB et al. Detection of life-threatening prostate cancer with prostate-specific antigen velocity during a window of curability. J Natl Cancer Inst. 2006 Nov 1;98(21):1521-7.
Graser A et al. MRI-based PSA Density and PSA Density of the Transitional Zone Compared With PSA Alone: Correlation With Prostate Cancer Gleason Score. J Comput Assist Tomogr. 2006 November/December;30(6):891-895.
Kline EE et al. Citrate concentrations in human seminal fluid and expressed prostatic fluid determined via 1H nuclear magnetic resonance spectroscopy outperform prostate specific antigen in prostate cancer detection. J Urol. 2006 Nov;176(5):2274-9.
LabTestsOnline®. PSA. [Homepage on the Internet] ©2001-2006. Last reviewed on January 28, 2005. Last accessed on November 7, 2006. Available at URL: http://www.labtestsonline.org/understanding/analytes/psa/sample.html
Rhoden EL et al. Influence of demographic factors and biochemical characteristics on the prostate-specific antigen (PSA) response to testosterone replacement therapy. Int J Impot Res. 2006 Mar-Apr;18(2):201-5.
U.S. Preventive Services Task Force Guidelines 2006 found at http://www.ahrq.gov/clinic/pocketgd.pdf
UTMB Laboratory Survival Guide®. PROSTATE SPECIFIC ANTIGEN, serum. [Homepage on the Internet]© 2006. Last reviewed on February 2006. Last accessed on November 21, 2006. Available at URL: http://www.utmb.edu/lsg/LabSurvivalGuide/chem/PSA_serum.html
WebMD®. Prostate-Specific Antigen (PSA). ©2005-2006. Last reviewed on August 9, 2005. Last accessed on November 7, 2006. Available at URL: http://www.webmd.com/hw/mens_conditions/hw5522.asp

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