Prostate Specific Antigen (cont.)

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What are age-specific reference ranges for serum PSA?

The use of age-specific PSA ranges for the detection of prostate cancer is controversial. Not all studies have agreed that this is better than simply using a level of 4.0 ng/mL as the highest normal value. Nevertheless, due to the age-related growth of the prostate, the concept of adjusting the cutoff values based on age has helped reduce unnecessary prostate biopsies in older men to improve early prostate cancer detection. Below are the suggested age-adjusted values based on age and race.

Age-Specific Reference Ranges for Serum PSA
Age Range (Years) Asian Americans African Americans Caucasians
40 to 49 0 to 2.0 ng/mL 0 to 2.0 ng/mL 0 to 2.5 ng/mL
50 to 59 0 to 3.0 ng/mL 0 to 4.0 ng/mL 0 to 3.5 ng/mL
60 to 69 0 to 4.0 ng/mL 0 to 4.5 ng/mL 0 to 4.5 ng/mL
70 to 79 0 to 5.0 ng/mL 0 to 5.5 ng/mL 0 to 6.5 ng/mL

How is PSA used for early detection prostate cancer?

Clinically localized prostate cancer generally does not usually cause any clinical symptoms. Men usually feel perfectly well and prostate biopsy to detect prostate cancer is commonly initiated by an abnormal prostate digital rectal examination and/or an abnormal PSA value. It is for this reason that early detection tests have been developed in order to detect prostate cancer while it remains clinically silent and confined to the prostate. Hence, in clinical practice, tests used to detect prostate cancer include serum PSA level, digital rectal examination (DRE) and transrectal ultrasonography (TRUS).

In particular, the level of PSA has been demonstrated to be an independent variable to predict the presence of prostate cancer. In fact, the higher the level, the more likely prostate cancer is present. An abnormal result will usually require additional testing. However, definitive diagnosis of prostate cancer depends on the presence of cancer cells obtained either from prostate biopsy or surgical specimens.

In general, PSA levels greater than 4 ng/mL are usually considered suspicious. As levels increase above 10.0 ng/mL, the probability of cancer increases dramatically. However, not all men with prostate cancer have elevated PSA levels. It is known that a small but significant number of prostate cancers can present with a PSA level of less than 4.0 ng/mL. This is why doctors may use lower thresholds to decide when to do a biopsy.

For an average man over the age of 50 with a normal digital rectal exam, the average probability of having prostate cancer detectable by prostate biopsy according to his PSA level is as follows:

Probability of Prostate Cancer Detectable by Biopsy According to PSA Level
PSA Level (ng/mL) 0 to 2.0 2.0 to 4.0 4.0 to 10.0 greater than 10.0
Prostate Cancer on Biopsy (%) 10% 25% 17% to 32% 43% to 65%

Since the likelihood of having prostate cancer increases proportionately with PSA level, there is no threshold below which a man can be reassured that prostate cancer does not exist.

In order to improve the specificity of the PSA test in the early detection of prostate cancer, several modifications of the serum PSA value have been described including the ratio of free/total PSA and the measurement of PSA change over time.

Medically Reviewed by a Doctor on 11/3/2015

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