Activity trackers are becoming increasingly popular in our society. People of all ages wear them to keep track of the steps they take, the number of hours of sleep they get at night, and now they can even track a person’s heart rate. As more people use activity trackers, the roles these trackers can play in medicine are becoming more apparent. Recently, an activity tracker was used to identify the time that a man went into atrial fibrillation, thus allowing doctors at his hospital to determine that it was safe to cardiovert him.1 Not only are these monitors useful for cardiology purposes, but they are also becoming an important tool in the world of hematology.

Activity trackers can also estimate the hemoglobin levels of patients who are prone to anemia. In conditions like Diamond Blackfan Anemia (DBA), a rare bone marrow disorder where red blood cells are not produced, a patient’s hemoglobin may differ week to week and may be unpredictable.2  People with DBA are either steroid dependent or transfusion dependent. Those who are steroid dependent are able to take steroids on a daily or semi-daily basis, and their bodies respond by producing red blood cells. Those who are transfusion dependent rely on blood transfusions, which they may need every couple of weeks or every couple of months. However, transfusion-dependent patients have hemoglobin levels that are often unpredictable. Patients who normally require a transfusion every couple of months may find that their bodies change, and they may develop a pattern where they require a transfusion about every 3 weeks. Usually, adult patients can tell when their hemoglobin is getting low based on how they feel, so they know when they need a transfusion. Unfortunately, in younger populations and elderly patients, family members often need to determine whether a patient’s hemoglobin is dropping. This is where activity trackers are beginning to play an important role.

Patients with DBA are now using activity trackers to help themselves and their families determine when they need a transfusion. This is being done by consistently monitoring the patient’s resting heart rate. With a little experience, patients are getting really good at correlating their heart rate to their hemoglobin. When their resting heart rate increases to a certain number, they know it is time to get a transfusion. The accuracy is astounding.

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This method provides a much easier way for patients and their families to estimate hemoglobin levels, instead of trying to estimate their hemoglobin based on how they look and feel. This advanced technology relies on one of the basic principles of medicine—using a vital sign to determine the health of a patient. I hope this concept finds its way into other areas of medicine, so that a patient can identify an increased heart rate and recognize that they need to seek medical attention. I love that activity trackers are easy for patients to use and I can’t wait to see how the medical world will use them next.

Jillian Knowles, MMS, PA-C is an emergency medicine physician assistant in the Philadelphia area.


  1. Rudner J, Mcdougall C, Sailam V, et al. Interrogation of Patient Smartphone Activity Tracker to Assist Arrhythmia Management. Ann Emerg Med. 2016;68(3):292-4.
  2. Vlachos A, Ball S, Dahl N, et al. Diagnosing and treating Diamond Blackfan anaemia: results of an international clinical consensus conference. Br J Haematol. 2008;142(6):859-76.