Principles of disease screening

The benefits must outweigh the potential harms, the screening program must be adapted to individual risks, and all projects should be prioritized with clear evidence-based support. All the remaining details revolve around these three sentences.

I met Aunt Zhang at a community free clinic last month. She is 52 years old. She has no family history of lung cancer and does not smoke. She usually dances square dances and is in good physical condition. I watched a live broadcast a while ago and bought a 9999 "anti-cancer screening package". She insists on getting a PET-CT, and she can't stop her. The result was a 3mm solid pulmonary nodule. The thoracic surgeon showed the film and said it was fine. She just needed to be reviewed every year. But she was still so scared that she couldn't sleep all night long. She lost 8 pounds in half a month. In the end, she had to do a puncture to feel relieved. As a result, the puncture also caused a slight pneumothorax, which was the old sin. This is a typical example of not understanding the screening principles and instead looking for trouble for yourself.

Don't just think about "early detection and early treatment", you also have to do some calculations first: Is there any radiation in this examination itself? Was there any trauma? What is the probability of false positives? Will the problem detected be an inert disease that will not occur in a lifetime even if it is not checked? For example, the prostate-specific antigen (PSA) screening, which was a hot topic in the past, has not come to a unified conclusion until now: European and American studies have said that PSA screening can indeed reduce the mortality rate of prostate cancer. However, there are also large sample data showing that for every prostate cancer that really needs treatment, more than 30 people will be fooled by false positive results. Either the puncture will be in vain, or the indolent cancer that does not need to be treated will be cut out. Instead, it will leak urine, affect sexual function, and greatly reduce the quality of life. The current general consensus in the industry is that men over 75 years old have a life expectancy of less than 10 years. There is no need to undergo PSA screening. Even if a problem is found, there is a high probability that it will not be the disease that affects your lifespan and you will not suffer from it.

Don’t apply foreign guidelines to yourself, after all, the risk profiles of different groups of people are very different. For example, for breast cancer screening, European and American guidelines generally recommend that women over 40 years old have annual mammography. However, Asian women generally have denser breasts, and the mammography target has poor penetrating power. Many small nodules cannot be detected at all, and instead they consume more rays. Many domestic breast doctors will recommend that Asian women under 40 years old give priority to ultrasound screening. There is also low-dose spiral CT for lung cancer screening. Previously, the U.S. Preventive Services Task Force (USPSTF) recommended that people over 55 years old and with a smoking history of more than 30 pack-years need to do it every year. Last year, the age was just lowered to 50 years old and the smoking history was 20 pack-years. But in the country In clinical scenarios, many thoracic surgeons will recommend that women over 45 years old, who have been exposed to kitchen fumes for a long time, or whose work environment is exposed to dust, can also be screened regularly. After all, Chinese women do not smoke, but the incidence of lung cancer is not low. If they apply European and American standards, it is easy to miss diagnosis. There is no "absolutely correct" answer at this time. The recommendations of different institutions are inherently different. Just choose the one that suits your own risks.

As for the "one drop of blood to check for whole body cancer" and "full set of tumor markers" promoted in the Internet celebrity packages, really don't do it blindly. These things are not supported by large-scale population evidence at all. If the test is high, it may not necessarily be cancer, and if it is normal, it may be missed. Apart from adding trouble to you, it has no practical use. I used to run two cancer screening projects in rural areas with the old director of CDC. He always told us: "Screening is not to find diseases for healthy people, but to plug loopholes for people at risk." If you don't have any high-risk factors, why are you just joining in the fun?

Of course, this does not mean that all items that are not in the guideline cannot be touched. For example, if a relative in the family has a rare genetic disease, then you should do a carrier screening in advance. Even if the guideline does not mention it, it will be no problem if you find a reliable geneticist to evaluate it. After all, the guideline is for the general population, and special situations should be treated specially.

When I recommend screening items to relatives and friends now, I never let them buy the packaged "all-in-one physical examination package". I always ask about age, family history, past medical history, and living habits before selecting items. Just like going through airport security, ordinary passengers can just go through a normal X-ray machine. If you have brought suspicious luggage or have a record of contraband, you need to open the bag for inspection and explosion-proof testing. If no one comes up, then all passengers will be searched, right? In the final analysis, it is better to ask a few questions before doing the screening and don’t be led astray by marketing rhetoric.