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Because screening tests must be confirmed by a confirmatory test, screening for a disease always leads to more testing. In many cases, these tests are invasive, either entailing radiation exposure ([[CT]] scan) or complicated patient preparation and discomfort during the procedure ([[colonoscopy]]). In some cases, for example with NIPT testing, the confirmatory test ([[amniocentesis]] or [[chorionic villus sampling]]) is invasive and increase the risk of harm ([[abortion]] of the foetus in this case), which may lead to harm for people who are actually healthy. | Because screening tests must be confirmed by a confirmatory test, screening for a disease always leads to more testing. In many cases, these tests are invasive, either entailing radiation exposure ([[CT]] scan) or complicated patient preparation and discomfort during the procedure ([[colonoscopy]]). In some cases, for example with NIPT testing, the confirmatory test ([[amniocentesis]] or [[chorionic villus sampling]]) is invasive and increase the risk of harm ([[abortion]] of the foetus in this case), which may lead to harm for people who are actually healthy. | ||
==== | ==== Early diagnosis may not always improve prognosis ==== | ||
It is reasonable to assume that early diagnosis always improves the prognosis, but that is not always the case. | It is reasonable to assume that early diagnosis always improves the prognosis, but that is not always the case. In many cases, the cancer would develop so slowly that the person would never have known of it, or possibly only developed mild symptoms. However, cancer diagnosis almost always leads to aggressive treatment, which has its own effects on quality of life. | ||
South Korea started screening for thyroid cancer in the late 20th century. Up until relatively recently, research showed that, while the incidince increased significantly (more cases of thyroid cancer were discovered), the mortality remained the same. In other words, screening detected more cases and lead to more people being treated for cancer, which is a burden to both the healthcare system and the individual, but screening could not demonstrate a reduction in mortality, which is arguably one of the most important goals of screening. This shows that screening can lead to significant overdiagnosis.<ref> | This is especially important for [[prostate cancer]], for example. Prostate cancer is relatively common in elderly, but research has shown that many who are treated for subclinical prostate cancer would never have developed symptoms of the cancer, and would rather have died peacefully, never knowing that they even had the cancer. Also important to consider that cancer treatment causes significant reduction in quality of life, which is especially unfortunate if the cancer would never have caused symptoms anyway. | ||
South Korea started screening for thyroid cancer in the late 20th century. Up until relatively recently, research showed that, while the incidince increased significantly (more cases of thyroid cancer were discovered), the mortality remained the same. In other words, screening detected more cases and lead to more people being treated for cancer, which is a burden to both the healthcare system and the individual, but screening could not demonstrate a reduction in mortality, which is arguably one of the most important goals of screening. This shows that screening can lead to significant overdiagnosis.<ref><nowiki>https://www.nejm.org/doi/full/10.1056/NEJMp1409841</nowiki></ref> | |||
== Diagnosis == | == Diagnosis == | ||