What is respiratory disease?
Respiratory disease covers conditions that damage the airways and lungs. Two matter most here: lung cancer, and chronic obstructive pulmonary disease (COPD), long-term narrowing of the airways, usually from smoking.
Only one of them has a proven screening test. Low-dose CT lowers lung-cancer deaths in heavy smokers (NLST). Taiwan also screens people with a family history, where the evidence is detection (TALENT), not fewer deaths. COPD is diagnosed with a breathing test once symptoms appear.
Why lung cancer is often found late
Lung cancer is the leading cause of cancer death worldwide. A tumor deep in the lung causes few symptoms until it is large or has spread, so many cases are found when cure is difficult. Screening eligible people can find some cancers earlier.
Who is most at risk
These raise the risk of lung cancer and COPD:
- Smoking — the biggest factor; risk climbs with years and amount, and falls slowly after quitting
- A family history of lung cancer in a parent, sibling or child
- Long exposure to air pollution, or to dust and fumes at work
A risk factor is not the same as a screening criterion. In Taiwan, pollution or cooking fumes alone do not qualify someone for the national program.
What screening can and cannot do
In the US National Lung Screening Trial, yearly low-dose lung CT in heavy smokers led to 20% fewer lung-cancer deaths than chest X-ray. It also finds many harmless spots.
- Small lung nodules, most of which are benign
- Some early lung cancers, before symptoms
- Diagnose COPD. A breathing test called spirometry does, when there are symptoms. The US Preventive Services Task Force recommends against screening for COPD in adults without symptoms.
- Tell every nodule's nature from one scan. Depending on size and growth, a nodule may need nothing more, a repeat scan, or a PET scan or biopsy.
- Replace a chest assessment for symptoms. A cough or breathlessness needs a doctor, who may order a diagnostic CT instead.
Who is eligible for lung screening
| Program | Who | How often |
|---|---|---|
| Taiwan (HPA) — family history | A parent, sibling or child with lung cancer; men 45–74, women 40–74 | Every 2 years |
| Taiwan (HPA) — smoking | Ages 50–74, 20+ pack-years (one pack a day for 20 years, or the equivalent), who currently smoke and are willing to quit, or who quit less than 15 years ago | Every 2 years |
| US (USPSTF 2021) | Ages 50–80, 20 pack-years, smoking now or quit within the past 15 years | Every year |
Taiwan's funded screening is for people with National Health Insurance who meet the criteria.
- Coughing up blood, or sudden severe breathlessness: call 119 in Taiwan, as in the box above.
- A cough lasting weeks, or breathlessness that is new or worsening: see a doctor soon.
- No symptoms, and you fit a row above: low-dose CT is worth discussing.
- No symptoms, and you fit no row: screening is an individual decision with a doctor, not an automatic recommendation.
