In the developing world, children and adults with leukemia and other disorders require frequent blood draws to determine if they need blood transfusions.

Doctors are interested in measuring hemoglobin, a protein found in red blood cells. To obtain this basic measurement, healthcare providers either have to draw blood with a needle or intravenous line or spend up to thousands of dollars on a specialized machine that measures hemoglobin non-invasively.

Now, electrical engineers and computer scientists from the University of Washington (UW) have developed HemaApp, which uses a smartphone camera to estimate hemoglobin concentrations and screen for anemia. In an initial trial of 31 patients, HemaApp performed as well as the Masimo Pronto, the more expensive U.S. Food and Drug Administration-approved medical device that non-invasively measures hemoglobin by clipping a sensor onto a person’s finger.

“In developing countries, community health workers have so much specialized equipment to monitor different conditions that they literally have whole bags full of devices,” comments electrical engineering doctoral student Edward Wang. “We are trying to make these screening tools work on one ubiquitous platform—a smartphone.”

By shining light from the phone’s camera flash through the patient’s finger, HemaApp analyzes blood color to estimate hemoglobin concentrations. The researchers tested the app under three different scenarios: using the smartphone camera’s flash alone, in combination with a common incandescent lightbulb and with a low-cost LED lighting attachment.

HemaApp’s hemoglobin measurements using a smartphone camera alone had a 69% correlation to a patient’s complete blood count (CBC) test, a 74% correlation when used under a common incandescent light bulb and an 82% correlation using a small circle of LED lights that can snap onto the phone. For comparison, the Masimo Pronto’s measurements had an 81% correlation to the blood test.

HemaApp draws on previous work from UW’s UbiComp lab, which also developed Bilicam, a mobile app that uses a smartphone’s camera and flash to infer the amount of bilirubin in the blood for newborn jaundice. The newer app bombards a patient’s finger with different wavelengths of light and infrared energy and creates a series of videos. By analyzing how colors are absorbed and reflected across those wavelengths, it can detect concentrations of hemoglobin and other blood components like plasma.

To ensure that it works on different skin tones and body masses, the team developed processing algorithms that use the patient’s pulse to distinguish between the properties of the patient’s blood and the physical characteristics of his or her finger.

The mobile app is not intended to replace blood tests, which remain the most accurate way to measure hemoglobin. But the early test results, from patients ranging in age from 6 to 77 years old, suggest HemaApp can be an effective and affordable initial screening tool to determine whether further blood testing is warranted.

Next research steps include wider national and international testing of HemaApp, collecting more data to improve accuracy rates and using smartphones to try to detect abnormal hemoglobin properties that could help screen for sickle cell disease and other blood disorders.

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