A simple finger test you can do yourself might help detect an underlying health issue, including lung cancer.
Known as the Schamroth window test, it identifies a rare deformity called “digital clubbing” or “finger clubbing,” often seen in people with certain heart or lung problems.
Cancer Research U.K. explains that finger clubbing develops in stages: first, the nail bed softens and the skin near it becomes shiny. Next, the nails curve more than usual when viewed from the side—this is called “Schamroth’s sign.” Finally, the fingertips may enlarge, sometimes described as “drumstick fingers.”
Scientists believe clubbing happens because fluid builds up in the soft tissue at the fingertips due to increased blood flow, although the exact cause isn’t fully understood.
Finger clubbing appears in about 35% of people with non-small cell lung cancer and 4% with small cell lung cancer. It’s also found in mesothelioma, a cancer affecting the lung lining and chest wall.
However, finger clubbing isn’t a sure sign of cancer. It can also result from lung diseases like cystic fibrosis, pulmonary fibrosis, bronchiectasis, asbestosis, as well as some heart defects, liver disease, or Crohn’s disease.
If you think you might have finger clubbing, the Schamroth window test is a quick, easy check—but it’s only a guide and not a substitute for professional medical advice.
Emma Norton from Bupa U.K. told the Huffington Post that the test, commonly used by doctors, can also be done at home in seconds.
To perform the test, hold your hands up and press your index fingers’ nails together so they touch face to face. Normally, you should see a small diamond-shaped gap between the nail beds.
If that gap is missing, it could indicate finger clubbing, which may suggest an underlying condition. In that case, it’s best to see a doctor promptly for a full evaluation.
