Imagine being able to perform a quick test with your own hands that could alert you to serious health issues like lung cancer or heart disease. Doctors are pointing to a simple, non-invasive method called the Schamroth window test, where you create a small diamond shape with your fingers.

This test helps detect finger clubbing, a condition linked to several life-threatening illnesses. According to experts, if the diamond-shaped gap is missing when you press your fingernails together, it could be a red flag. Changes like shiny skin around the nails, spongy nail beds, or downward-curving nails could be your body’s way of signaling trouble. But what exactly causes these changes—and what conditions are they connected to? Here’s where things get really interesting…

Finger clubbing is often a result of long-term low oxygen levels in the blood, known as hypoxemia. It’s been observed in patients with lung cancer, mesothelioma, chronic lung diseases like cystic fibrosis, and even heart conditions such as congenital heart defects. Liver and gastrointestinal diseases like Crohn’s and cirrhosis have also been linked.

To try the test yourself, press your index fingernails together and look for a diamond-shaped gap. If it’s not there, it’s worth seeing your doctor. While this isn’t a diagnosis, it’s a potentially lifesaving clue. As oncology nurse Emma Norton says, it’s a sign not to ignore. So why not take a moment, try it yourself, and share this test with others—it might just help someone catch a problem early.