Fingernails – a window into your blood health Gianni Diliberto/Getty

A smartphone app can diagnose anaemia by analysing the colour of a person’s fingernails in a photograph.

Anaemia – a condition in which people have low levels of haemoglobin or not enough healthy red blood cells – affects over two billion people worldwide. If untreated, it can cause severe fatigue, heart problems and complications in pregnancy.

Tests for anaemia require blood samples and specialised equipment that can be hard to access in the low income societies where anaemia is most prevalent. Wilbur Lam of Emory University, Atlanta, and colleagues wondered if smartphones could offer a simple alternative.


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Previous studies have shown that the degree of paleness in some body tissues, including the fingernail beds, is a reliable indicator of how anaemic someone is. The skin beneath fingernails does not contain pigment, so haemoglobin – the oxygen-carrying pigment of the blood – is the main source of colour.

The app allows people to obtain a haemoglobin measurement in seconds by photographing their fingernails and tapping the screen to indicate where the nails are in the image. It uses the photo metadata to account for and factor out ambient lighting conditions.

“Because it requires only a smartphone, our app enables anyone to screen themselves for anaemia at any time – all they need to do is download the app,” says Lam.

Screening tool

The measurement is based on a database of photos of fingernails from people with known haemoglobin levels. Although not as accurate as a blood test, it may be sensitive enough to be useful for screening groups that have a high risk of anaemia, such as the elderly, pregnant women and young children. However, it will need further testing with larger numbers of people to confirm its accuracy before being widely used.

The app can be made more accurate by personalising it with a specific person’s measurements. That could make it useful for people who have been diagnosed to monitor their anaemia painlessly at home, says Lam.

Lam’s team are also working on using smartphones to assess jaundice, a yellowing of the skin and eyes caused by liver disease.

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Journal reference: Nature Communications, DOI: 10.1038/s41467-018-07262-2