Some background information may be needed for interpretation and classification, along with an explanation of technical terms. In a medical-diagnostic context, sensitivity specifically indicates how many diseases or “abnormalities” are detected, while specificity indicates how many healthy individuals are correctly identified as healthy. As described in our analysis of the Apple Watch’s blood pressure function, these two values are related. Diagnostic procedures can be optimized for higher sensitivity or specificity within certain limits, provided that the procedure is generally suitable. In a screening procedure such as the detection of atrial fibrillation, high sensitivity should be clearly prioritized over high specificity, at least from the individual patient’s perspective. While a false-positive result might lead to wasted waiting time at the doctor’s office and an unnecessary ECG, this is, of course, a far better alternative to the increased risk of mortality associated with undetected atrial fibrillation.
Background information on the study
The study is a systematic review, meaning that Barrera N et al. did not take any measurements themselves, but rather reviewed existing studies and included them in the evaluation (or not). The advantages of such studies are that the number of cumulative participants is very high and the number of different brands/devices tested is greater. At this point, we would like to clearly point out that this review cumulates different, specific model variants from individual manufacturers and that the number of test subjects per specific device varies greatly in some cases. Furthermore, the measurement methods used in the individual studies are not always the same. The study by Barrera N et al. is currently still in the preprint stage and so has not yet been peer-reviewed. Lastly, the research landscape may still change if, for example, new devices come onto the market.
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