Prostate health index reference value

The prostate health index (phi) is a comprehensive screening index calculated from three indicators: total PSA, free PSA, and prostate-specific antigen precursor p2PSA. The accuracy of prostate cancer diagnosis is more than three times higher than that of measuring PSA alone. Currently, the reference cutoff value commonly used in domestic urology clinics is 2. 6ng/ml. Below this value, the risk of prostate cancer can basically be judged to be extremely low. 2.6~10ng/ml belongs to the risk gray area and needs to be comprehensively judged in conjunction with other indicators. If it is higher than 10ng/ml, the probability of prostate cancer exceeds 30%. It is recommended to give priority to prostate biopsy for further investigation.

I just met a 48-year-old programmer, Lao Chen, in the outpatient clinic last week. His total PSA (prostate-specific antigen) in the physical examination was 4.2ng/ml, which was 0.2 higher than the upper limit of normal. He was so frightened that he couldn't sleep for three days in a row. He went to two hospitals and asked him to do a puncture. Finally, he came to me for a phi check, and the result was 1.8. I just asked him to have a routine review in six months. There was no need to suffer a puncture.

When talking about this, someone will definitely ask, why is the critical value of phi in the information I checked before is 4? This is actually an area where the industry has not yet fully unified. A few years ago, the NCCN guidelines in the United States raised the threshold to 4ng/ml. The reason is that the threshold of 2.6 is too low, which easily leads to unnecessary punctures for many people who have no problems at all, but increases the risk of infection and bleeding. ； Some tertiary hospitals in China also use 3.1 as the critical value, and some grassroots hospitals will directly use the reference range that comes with the test kit because the calibration standards of the test reagents are different, and will not impose the standard of 2.6 at all. My own clinical habit is to first look at the institution's reference value marked on the test form. That is the most accurate reference that matches the testing equipment. The values ​​found online can only be used as a rough reference.

In fact, there is really no need to stick to a number. phi is a risk indicator, not the gold standard for diagnosis. I met a 28-year-old guy a while ago. His PSA was high when he urinated frequently and urgently. The phi test showed 2.9, which is a little higher than 2.6. When I asked, he just rode a 20-kilometer mountain bike the day before and his prostate was squeezed. I asked him to rest for two weeks and then check again, and the result dropped directly to 1.7. Similarly, those who have recently drank alcohol, stayed up late at night, had a digital rectal examination, or had a urinary catheter inserted may cause the phi to temporarily increase. At this time, the value is inherently inaccurate, and rash punctures are completely worth the loss.

There is now a group of scholars who are recommending reference values ​​stratified by age. For example, the threshold value should be set to 2.5 for those under 50 years old, 2.7 for those between 50 and 60 years old, and 3.0 for those over 60 years old. After all, the probability of young people getting prostate cancer is extremely low. Even if the value is slightly higher, it is basically caused by prostatitis or hyperplasia. The elderly themselves are a high-risk group for prostate cancer, so they must be vigilant even if the value is slightly lower. Opponents have their reasons. They feel that stratification is too complicated. Doctors in grassroots hospitals are already busy. Using a unified standard is less likely to make mistakes. Patients in gray areas can be observed twice more and their condition will not be delayed. Both statements are reasonable, and there is no absolute right or wrong. It mainly depends on the doctor's clinical experience.

To put it bluntly, the reference value of phi is like our threshold for detecting drunk driving. Below 20mg/100ml is normal, 20~80 is the gray area of ​​drunk driving, and above 80 is drunk driving. But if you just ate two egg yolk pies and the test is 25, you can't be directly counted as a drunk driver, right? You have to retest, and you have to judge based on the actual situation of whether you have been drinking. The reference value of phi is also the same.

One last thing to mention, if you have difficulty urinating, nocturia more than three times, or perineal swelling, even if the phi value is within the reference range, you should see a urologist. After all, the indicators are just cold numbers, and your own physical feelings are the most worthy of attention. Oh, by the way, men over 50 years old, or men over 45 years old with a family history of prostate cancer, it is best to check phi once a year. The accuracy is much higher than checking the total PSA alone, and can save a lot of detours.