Is disease screening considered secondary prevention?

The current mainstream consensus in the public health field is that most disease screenings fall into the category of secondary prevention. However, there are also a few special screening scenarios where classification disputes exist.

The core of secondary prevention is what we often call the "three early" prevention of early detection, early diagnosis, and early treatment. The goal is to detect the disease in the early clinical stage of the disease and before obvious symptoms appear, and to intervene in a timely manner to block the progression of the disease and avoid developing into a more serious disease. The "two cancer screenings" for cervical cancer and breast cancer that we are most exposed to in daily life, free fecal occult blood screening arranged by the community for people over 40 years old, low-dose spiral CT lung cancer screening, as well as thyroid ultrasound, blood sugar and lipid screening in routine physical examinations, all fall into this category. The year before last year, when I was doing follow-up screening for two cancers in the community, I met a 38-year-old woman who didn't feel any discomfort at all. She just came to participate in the free screening and was diagnosed with high-grade cervical intraepithelial neoplasia.

However, this classification is not without different opinions. The core disagreement actually lies in the purpose of some special screenings. For example, when couples are screened for carriers of single-gene genetic diseases before pregnancy, many carriers themselves will not develop the disease at all and do not need treatment. The purpose of screening is to assess the risk of disease in the next generation, make fertility decisions in advance, and avoid the birth of children with severe disease at the root. This is actually more in the category of primary prevention (that is, prevention of causes). Many colleagues in maternal and child public health will also classify this type of screening as an extension of primary prevention. There are also pre-marital syphilis and HIV screenings. In addition to early detection and intervention for infected persons, they also have the effect of cutting off the paths of sexual transmission and mother-to-child transmission. This is equivalent to stepping on the boundary between primary and secondary prevention at the same time, and cannot be lumped into a certain category.

In fact, when we usually work on public health projects, we don’t stick to the rules of classification. After all, definition is dead, and prevention and control is living. No matter which category it is classified into, it is most practical to allow everyone to actively participate in screening and prevent serious illness.