disease screening census

The core essence of disease screening and census is to "use the minimum public health cost to detect and intervene in reversible health risks at the population level early." It is by no means "the more complete the examination, the wider the coverage, and the higher the frequency, the better." Blind screening without evidence will lead to excessive medical treatment, waste of resources, and even unnecessary physical and mental burdens on the subjects.

I encountered something like this when I was stationed at a county disease control center in Zhejiang a while ago: At that time, the county had just approved a public health fund, and the officer in charge was very motivated. He wanted to do a full set of diabetes screenings for all elderly people over 60 years old in the jurisdiction - fasting blood glucose, glycated hemoglobin, and an OGTT glucose tolerance test. The cost per person was almost 200 yuan. At first, I felt that many potential patients would be screened out. As a result, a pilot project was conducted in two towns. The number of confirmed cases screened out was not as many as the elderly people who passed out after drinking sugar water and were sent to the rest area. The final positive predictive value was only 2.3%, which is equivalent to screening 43 people to find one true diabetic patient. The rest were either false positives or just had slightly high blood sugar and did not need to take medicine. Instead, community doctors were required to call one by one to explain the follow-up, which took up half of the energy usually spent on visiting hypertensive patients to measure blood pressure. Finally, we quickly changed the plan to screen fasting blood glucose first, and then conduct follow-up examinations if it exceeded 6.1. The cost was directly reduced by 70%, and the detection rate increased by three times.

In fact, the public health and clinical fields have always had different considerations regarding the scale of screening. Public health scholars pay more attention to the overall benefits at the population level. For example, the WHO has clear data: as long as 70% of women aged 35-64 in a region receive regular cervical cancer screening, the local cervical cancer mortality rate can be reduced by more than 60%. In this case, even if there are a small number of false positive cases that require follow-up review, the overall input-output ratio is high enough and worthy of full promotion. But the perspective of a clinical doctor is different. Last week I had dinner with Director Li of the Breast Department of a tertiary hospital. He also complained that in the past six months, he had received nearly 20 girls around the age of 25. They all had mammography examinations and reported Category 4a nodules. They were so frightened that they cried and rushed to register. After the ultrasound, it turned out to be ordinary breast hyperplasia, and they did not even need to prescribe medicine. He said that the mammography target itself contains radiation and is particularly less sensitive to the dense breasts of young women. Originally, the guidelines recommended that patients over 40 years of age should consider the procedure. Now, in order to increase prices, many medical examination institutions dare to include any item in the package, without any evidence-based basis.

Over the years, China has developed many successful screening models and encountered many pitfalls. For example, Shanghai has been conducting colorectal cancer screening for more than ten years, and the model is very mature: all residents over 50 years old are first given a risk questionnaire + fecal occult blood test, and high-risk groups screened out undergo colonoscopy for free. Calculating that every 1 yuan invested in screening costs can save 11 yuan in subsequent treatment costs for late-stage colorectal cancer, and can also prevent many families from becoming impoverished due to the disease. However, in the past few years, many places have followed the trend and implemented national tumor marker screening. A tube of blood was drawn to test more than a dozen items, and the final false positive rate was as high as 30%. Many people found out that a certain indicator was high, and did a lot of tests without any problems. Instead, they lost trust in the screening. Later, they did not go to the hospital when they did have symptoms, which was not worth the gain.

I had a deep understanding of this when I helped neighborhood communities adjust elderly screening programs two years ago. At the beginning, the plan was uniformly issued by the superiors. It required checking blood pressure, blood sugar, blood lipids, electrocardiogram, lung cancer risk questionnaire, and osteoporosis screening. As a result, on every screening day, after the blood pressure and blood sugar were measured, the elderly felt that the queue was too long and left. The participation rate for the subsequent core projects was less than 30%. Later, we simply changed the rules: Elderly people over 60 years old and with a smoking history of more than 20 years were directly issued free coupons for low-dose CT scans. Other elderly people only had blood pressure, blood sugar, and blood lipids checked. Those who were willing to fill in the lung cancer risk questionnaire were given 10 eggs. In the end, the overall participation rate directly increased from 32% to 67%, and eight more patients with early-stage lung cancer were screened out. All of them are doing well after the surgery.

There is still a lot of controversy in the direction of whether ordinary people should do disease-related genetic screening. Supporters believe that the cost of sequencing has now dropped to a few hundred yuan. If the BRCA1/2 gene mutation is detected, a breast ultrasound + mammography half a year in advance, or preventive resection if necessary, can reduce the risk of breast cancer by more than 90%, which is a huge benefit. The opposing faction used data to speak, saying that the probability of BRCA mutations in the general population is less than 0.3%. If everyone is tested, people with false positives will be burdened with "cancer-prone constitutions". In the past two years, a girl was diagnosed with a BRCA mutation, and she had both breasts removed without seeing a clinical doctor for evaluation. In the end, she learned that the pathogenicity of the mutation at that site was very low, so there was no need for surgery, and it was too late to regret. The current consensus in the industry is that only high-risk groups with family histories need to undergo this type of genetic screening. There is really no need for ordinary people to join in the fun.

In fact, after all, disease screening and census has never been a question of "should it be done", but a question of "who should it be done for, what should be done, and how to do it". We in public health often say that if you spend an extra dollar on prevention, you can spend ten dollars less on treatment. But the premise is that the dollar must be spent in the right place. Otherwise, if you spend money to do bad things, the gain will outweigh the loss.