Screening
Testing people without symptoms, to find disease before it declares itself. Which programmes are worth it, for whom — and what they cost in false positives and overdiagnosis.
The figures at a glance
What screening is, and is not
Screening means testing people without symptoms, to find a disease before it declares itself. It is a different thing from a diagnostic test, which is done when there is already a finding or a symptom.
The distinction matters practically. If you have a symptom that worries you, you do not wait for the next scheduled screening round — you see your doctor.
The programmes with established benefit
- Breast — mammography, typically every two years between 50 and 69, extended to younger and older groups case by case.
- Cervix — HPV DNA testing, which has largely replaced the conventional Pap smear as the primary test.
- Colorectal — faecal immunochemical testing (FIT) at regular intervals, with colonoscopy when the result is positive.
- Lung — low-dose CT, only for high-risk groups with a heavy smoking history.
In Greece, breast, cervical and colorectal screening is organised through the national “Prolamvano” programme, which invites the relevant age groups.
The limits: overdiagnosis and false positives
Screening is not without cost, and an honest account of it includes the downsides.
- False positives — findings that lead to further tests and anxiety, and turn out to be benign.
- Overdiagnosis — finding tumours that would never have caused harm in a person’s lifetime, but which are treated because we cannot tell which ones they are.
- False negatives — no test finds everything, and a normal result does not cancel out a new symptom.
Even so, for the organised programmes listed here the overall balance of benefit and harm is well established as positive in the age groups for which they are recommended. The aim is not to test everyone for everything, but the right people for the right things.
Frequently asked questions
Should I have a whole-body scan or a “cancer check-up”?
It is not recommended as general screening. Whole-body imaging in people without symptoms produces a large number of incidental findings that lead to further investigation without a demonstrated survival benefit.
My test last year was normal. Do I need to repeat it?
Yes, at the interval each programme specifies. Screening works because it repeats; a normal result describes one point in time.
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