How to interpret PSA test indicators?

As people become more aware of health management, medical checkups have become an essential part of their daily lives. The PSA is an important test in men’s medical reports, and today we’ll learn about the “past life” of the PSA.

PSA is short for Prostate Specific Antigen, which translates to prostate specific antigen.

As early as 1971, Japanese scholars isolated a specific protein from semen and named it “gamma-seminal protein”.

In 1979, Wang et al. showed that PSA isolated from prostate tissue was the same protein as “γ-seminal protein”.

In 1980, the concentration of PSA in serum could be measured.

Since 1988, PSA has been widely used as a tumor marker for prostate cancer.

Tumor markers help us diagnose tumors early, such as alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA), which are clinically recognized as important indicators for diagnosing liver and rectal cancer, respectively. So, does PSA have a special ability to diagnose prostate cancer?

PSA is found only in prostate epithelial cells and is organ-specific but not tumor-specific, as both benign and malignant prostate disease may elevate serum PSA values. Therefore, it is very important to correctly interpret the serum PSA in the physical examination report.

Timing of PSA testing

The consensus among national and international experts is to perform annual serum PSA screening and transanal rectal prostate exams in men over 50 years of age, and for men with a family history of prostate cancer, to start these exams annually earlier than 45 years of age.

While some diseases (such as stomach cancer and kidney cancer) are trending younger, overall, prostate cancer is still more prevalent in older men.

For young and middle-aged men under the age of 40, the PSA test is primarily a response to inflammation of the prostate. In the clinical setting, PSA can be used as an indicator of efficacy in young and middle-aged men with persistent prostatitis.

Possible factors affecting serum PSA

Some factors can affect the value of serum PSA and should be avoided before blood is drawn. Experts recommend that PSA be measured 24 hours after ejaculation, 48 hours after cystoscopy or catheterization, 1 week after transanal rectal prostate finger examination, 1 month after prostate puncture biopsy, and to exclude acute prostatitis episodes and urinary retention.

Interpretation of PSA indicators

PSA is “bound” and “unbound” in the serum. The vast majority of PSA forms complexes with antiprotein hydrolases and macroglobulins, which is the “bound” PSA, while the remaining “unbound” PSA is free PSA, abbreviated fPSA (free-PSA).

The sum of the “bound” and “free” PSA is the total PSA (tPSA, total PSA). The normal reference value is usually tPSA less than 4ng/ml, both nationally and internationally.

According to European and American data:

When tPSA is less than 4ng/ml the likelihood of prostate cancer is less than 2%;
When tPSA is less than 4ng/ml the likelihood of prostate cancer is less than 2%;

When tPSA is between 4 and 10ng/ml, the likelihood of prostate cancer is about 25%;

and when tPSA is between 4 and 10ng/ml, the likelihood of prostate cancer is about 25%;

When tPSA is greater than 10 ng/ml, the likelihood of prostate cancer is about 67%.

The incidence of prostate cancer in the Chinese population is relatively low, with data suggesting a positive prostate puncture rate of 15.9% for a serum tPSA of 4 to 10ng/ml.

Serum PSA is influenced by factors such as age and prostate size, and age-specific tPSA values for each age group in our patients with BPH are:

0 to 1.5 ng/ml for ages 40 to 49 years;

0-3.0ng/ml for ages 50-59;

0~4.5ng/ml for 60~69 years old;
0~4.5ng/ml for 70~79 years old;

0~5.5ng/ml for ages 70~79;

0~8.0ng/ml for >80 years old.

This produces a gray zone (PSA 4 to 10ng/ml) for prostate cancer determination, within which the following PSA-related variables are recommended for reference:

1) Free PSA (fPSA): fPSA and tPSA are routinely measured simultaneously.

Most studies have shown that fPSA is an effective way to improve the detection of prostate cancer in the gray zone of tPSA levels. When serum tPSA is between 4 and 10 ng/ml, fPSA levels are negatively associated with the incidence of prostate cancer.

Studies have shown that when a patient’s tPSA is in the gray zone:

If fPSA/tPSA is less than 0.1, the patient has a 56% chance of developing prostate cancer;

In contrast, if fPSA/tPSA is greater than 0.25, the likelihood of prostate cancer is only 8%.

Domestically, an fPSA/tPSA greater than 0.16 is recommended as a normal reference (or critical) value.

2) PSA density (PSAD): the ratio of total serum PSA value to prostate volume.

Prostate volume is calculated by rectal ultrasonography. a normal PSAD value is less than 0.15, and PSAD helps to differentiate between elevated PSA due to prostate hyperplasia and prostate cancer.

When a patient’s PSA is at the high limit of normal or mildly elevated, the PSAD is used to guide the physician’s decision to perform a biopsy or follow-up.

3) PSA velocity (PSAV): This is the continuous observation of changes in serum PSA levels, which are significantly higher in prostate cancer than in prostate hyperplasia and normal subjects.

The normal value is less than 0.75ng/ml/year. If PSAV is greater than 0.75ng/ml/year, prostate cancer should be suspected.

PSAV is more appropriate for younger patients with low PSA values.

Test PSA at least 3 times in 2 years: PSAV calculation formula: [(PSA2-PSA1) + (PSA3- PSA2)]/2.

In summary, PSA abnormalities found on physical examination should be reviewed at a regular hospital for PSA review, and clinicians will make individualized analysis and diagnosis based on individual circumstances. There is no need for individuals to have blind panic, just adjust your mindset and follow the advice of your specialist.