Principles and methods of disease screening

The benefits always outweigh the risks, the screening program is adapted to the characteristics of the population, and the screening standards are dynamically adjusted along with the disease spectrum.； The core practical methods are implemented in three directions: hierarchical precise screening, multi-technical joint verification, and full-process follow-up closed loop. This is the largest consensus reached in the public health field and clinical academic circles at home and abroad.

To be honest, "the benefits outweigh the risks" is the prerequisite for all screening projects to be approved. Without this premise, no detection method, no matter how accurate it is, cannot be promoted routinely. In the past few years, high-end medical examination institutions have been very hyped about "PET-CT full-body cancer screening". The industry has been arguing for almost ten years without a unified opinion: one group believes that for high-risk groups with a clear family history of cancer and suspected symptoms, the benefits of early diagnosis of PET-CT are far greater than the radiation risks, and it can identify tiny metastases that cannot be found by ordinary CT. ； The other group is firmly against ordinary healthy people having it done every year. After all, the radiation dose of a whole-body PET-CT is about 10-20mSv, which is equivalent to hundreds of times of ordinary chest X-rays. Doing it for healthy people may increase the probability of radiation-induced cancer. The compromise that everyone can basically reach now is: routine screening is absolutely not recommended for the general population, and high-risk groups should also have their indications evaluated by doctors before doing it.

When I was working on a lung cancer screening project at a community public health station two years ago, many residents asked, "Can everyone do PET-CT to detect accurately?" We patiently tried to persuade them for a long time. The final plan was to first conduct questionnaire scores on smoking history, occupational exposure history, and family history. Those who scored high-risk would then undergo low-dose spiral CT. The radiation dose is only 1/3 of ordinary CT, and the accuracy is enough to screen out early-stage lung cancer. In that project, a total of 8 patients with early-stage lung adenocarcinoma were screened out, and all underwent minimally invasive surgery in a timely manner. The prognosis was very good, and other low-risk residents were not exposed to unnecessary radiation risks.

This actually involves the second principle: the screening program must be adapted to the characteristics of the population. Nowadays, in order to sell packages, many medical examination institutions don't care about your age, gender, or occupation. They just put in whatever items are expensive. A 20-year-old girl will prescribe you a prostate-specific antigen (PSA) test, and a 50-year-old man will give you an HPV typing test. It's not that these items are not good, but they are useless to you. Last month, I met a 28-year-old girl who came to consult with a 999 yuan "full physical examination package" that she grabbed in the live broadcast room. I looked at the list of items and laughed, and asked her if she placed the order without looking at the product details. Only then did she realize that she, a girl, didn't need to check prostate-related indicators. Take HPV screening as an example. The current consensus in the industry is that women under the age of 25 do not need routine screening at all. Most infections in this age group are transient and can be cleared by their own immunity. If they test positive, they will feel anxious. ； Unless men have high-risk sexual behaviors or have perianal lesions, there is little point in checking for HPV and it is a complete waste of money.

Moreover, screening standards are never static and must be dynamically adjusted as the disease spectrum changes. In the past, the standard for breast cancer screening was that only women over 40 years old were recommended to undergo mammography every year. Now the age of onset of breast cancer in my country is about 10 years earlier than in Europe and the United States, and the incidence rate among 30-35-year-olds is increasing year by year. Therefore, the latest Chinese Anti-Cancer Association guidelines recommend that women over 35 years old with a family history of breast cancer, menarche earlier than 12 years old, nulliparous, or those whose first childbirth is older than 35 years old, can include breast cancer screening in their annual routine physical examinations without waiting until the age of 40. Standards are dead, but people are alive. The disease spectrum is changing, and the boundaries of screening must also change. We cannot stick to the guidelines from ten years ago.

As for how to carry out screening, the more complete the better, the more comprehensive screening is really not the best. What we do most now is hierarchical screening. For example, if you do a group inspection for an Internet company, there are 996 young people every day. It is useless for you to check a bunch of geriatric diseases for them. Focus on adding sleep breathing monitoring, cervical spine MRI screening, and thyroid ultrasound. It is more practical than anything else. ； If we screen front-line workers in chemical plants, we should focus on checking blood counts, lung function, tumor markers corresponding to occupational exposure, and screening for occupational-related skin diseases. This can be said to be targeted.

Many people think that screening is just a test. In fact, this is not the case. The false positives and false negatives of a single technology are very high, and multiple technologies must be jointly verified to reduce errors. For example, for colorectal cancer screening, if you only do the traditional chemical method to detect hidden blood, even if you eat duck blood, you may get a positive result, which is a waste of time. ； If we directly ask everyone to undergo colonoscopy, medical resources will not be enough, and many people will suffer unnecessary suffering. Our current routine is to first do an immunotherapy for fecal occult blood (not affected by food) + risk questionnaire assessment. If one of these two is abnormal, then do a blood test for Septin9 gene methylation. If it is still positive, we recommend a colonoscopy. In this way, the false positive rate is reduced to less than 5%, and a lot of medical resources are saved.

There is also the most easily overlooked point: screening is not the end of the test, follow-up is the key. I met an aunt last year, and her fasting blood sugar in the community screening was 7.2mmol/L. We called her three times to ask her to go to the hospital for a glucose tolerance test. She felt that she didn't feel any discomfort and that the test must be wrong. Finally, we asked a community grid worker to come to persuade her and then went for a test. She was diagnosed with early type 2 diabetes. Because she was discovered early, she didn't need to take medicine, and her blood sugar was stabilized by controlling her diet and exercising. If we had not pursued her at that time, complications might have occurred in two or three years, and the significance of screening would have been completely missed.

Of course, there are still many controversial issues in the field of screening, such as whether the general population should routinely check for tumor markers. One group believes that false positives are too high. 90% of mild elevations are caused by inflammation, staying up late, etc., and finding out will only make people anxious. ； The other group believes that for people with a family history, the dynamic changes in tumor markers are an important reference. For example, if CEA (carcinoembryonic antigen) has increased year by year for three consecutive years, even if it is within the normal range, one should be alert to the presence of gastrointestinal lesions. At present, there is no completely unified conclusion in the industry. Most of them recommend that it be determined according to the individual's risk level. High-risk groups can be added, but ordinary healthy people do not need to make it a required check item.

To put it simply, disease screening is essentially a matter of "clearing mines". The more expensive the detector, the better, nor the wider the scanning range, the better. The solution that is suitable for your "land" is the one that can really find mines without blowing up the ground. If you are not sure what to check, chatting with a reliable general practitioner for 10 minutes will be much more useful than the 10,000 yuan package you grabbed in the live broadcast room.