Biomedical engineers have developed a smartphone app for the non-invasive detection of anemia. Instead of a blood test, the app uses photos of someone's fingernails taken on a smartphone to accurately measure how much hemoglobin is in their blood. The results are published in Nature Communications.

"All other 'point-of-care' anemia detection tools require external equipment, and represent trade-offs between invasiveness, cost, and accuracy," says the principal investigator. "This is a standalone app whose accuracy is on par with currently available point-of-care tests without the need to draw blood."

"Treatment for my disease requires monthly blood transfusions," the lead author says. "My doctors would test my hemoglobin levels more if they could, but it's a hassle for me to get to the hospital in between transfusions to receive this blood test. Instead, my doctors currently have to just estimate when I'm going to need a transfusion, based on my hemoglobin level trends."

Researchers say that their app could facilitate self-management by patients with chronic anemia, allowing them to monitor their disease and to identify the times when they need to adjust their therapies or receive transfusions, possibly reducing side effects or complications of having transfusions too early or too late.

The researchers say that the app should be used for screening, not clinical diagnosis. The technology could be used by anyone at any time, and could be especially appropriate for pregnant women, women with abnormal menstrual bleeding, or runners/athletes. Its simplicity means it could be useful in developing countries. Clinical diagnostic tools have strict accuracy requirements, but researchers think that with additional research, they can eventually achieve the accuracy needed to replace blood-based anemia testing for clinical diagnosis.

Anemia is a blood condition that affects two billion people worldwide and can lead to fatigue, paleness and cardiac distress if left untreated. The current gold standard for anemia diagnosis is known as a complete blood count (CBC).

The researchers studied fingernail photos and correlated the color of the fingernail beds with hemoglobin levels measured by CBC in 337 people: some healthy, and others with a variety of anemia diagnoses. The algorithm for converting fingernail color to blood hemoglobin level was developed with 237 of these subjects and then tested on 100.

A single smartphone image, without personalized calibration, can measure hemoglobin level with an accuracy of 2.4 grams/deciliter with a sensitivity of up to 97 percent. Personalized calibration, tested on four patients over the course of several weeks, can improve the accuracy to 0.92 grams/deciliter, a degree of accuracy on par with point-of-care blood-based hemoglobin tests. Normal values are 13.5-17.5 grams/deciliter for males and 12.0-15.5 grams/deciliter for females.

In the app, the use of fingernail beds, which do not contain melanin, means the test can be valid for people with a variety of skin tones. The accuracy is consistent for dark or light skin tones, the author says. The app uses image metadata to correct for background brightness, and can be adapted to phones from multiple manufacturers.

Researchers are working with a variety of doctors -- geriatric, internal medicine, neonatologists, transfusion medicine, global health -- to obtain additional data and better calibrate their system.

https://news.emory.edu/stories/2018/12/anemia_detection_by_phone/index.html

https://www.nature.com/articles/s41467-018-07262-2#Abs1

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