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Community screening for atrial fibrillation using a smartphone-based electrocardiogram (ECG) recorder turned up previously undetected cases in Hong Kong.

While some participants had previously known about their atrial fibrillation, another 0.8% of the study population received a new diagnosis of atrial fibrillation with the AliveCor single-lead ECG system -- a smartphone app and attached device featuring two ECG electrodes.

More than half (65.3%) of those with newly diagnosed atrial fibrillation were asymptomatic, reported , and , both of Princess Margaret Hospital in Hong Kong, in their study published online in .

The smartphone-based system detected atrial fibrillation in 1.8% of screened participants. Combined with self-reported cases of atrial fibrillation, there was a 8.5% total prevalence of atrial fibrillation in the community study.

"This category of atrial fibrillation likely represents both non-paroxysmal and paroxysmal atrial fibrillation," Chan and Choy suggested. "Interestingly, these prevalence rates are comparable with those observed in some recent studies on the US and European populations but much higher than those reported in studies on the Chinese population."

Furthermore, just 0.4% of people screened had uninterpretable ECGs with the app, the investigators added.

The 13,122 Hong Kong citizens in the study who voluntarily participated from 2014 to 2015 were invited and recruited for screening using media campaigns.

"Since we do not have in-depth information on the advertisement campaign, it is somewhat difficult to validate the effectiveness," , and , both of Danderyd's University Hospital in Sweden, wrote in an accompanying editorial. "Using media campaigns and advertisement for recruitment also infers a risk of bias in participation since the invitee exposure to the campaign is not equally distributed in the population."

Svennberg and Engdahl also noted the 50% rate of participation for systematic atrial fibrillation screening programs in Europe, a figure that is lower than what is seen for other screening measures. As for why fewer people choose to participate in atrial fibrillation screening studies, they suggested a combination of three factors: reluctance to participate in a trial of an non-mainstream procedure; lack of atrial fibrillation awareness; and difficulties traveling independently to screening centers due to age and frailty.

Chan and Choy did affirm in their study that age was a predictor for a positive atrial fibrillation screen from the smartphone app.

"We found that age was a variable with good discriminative ability for newly diagnosed atrial fibrillation with an AUC of 0.768 in screening the general population. On the other hand, we observed a steep rise in the prevalence of atrial fibrillation from the age of 60 onwards with a sensitivity of 98% and specificity of 29.2% in detecting newly diagnosed atrial fibrillation. This may serve as an age cut-off criterion to improve the cost-effectiveness of atrial fibrillation screening in the community."

Limitations of the non-randomized study, Chan and Choy wrote, included: "The participants self-reported their medical history, including history of atrial fibrillation and other comorbid conditions. The information provided might not be accurate and a significant proportion of participants did not know whether they had a history of atrial fibrillation. Single lead ECG with single-lead tracing was used in the diagnosis of atrial fibrillation. No conventional 12-lead ECG was performed as reference."

Nonetheless, Svennberg and Engdahl commented that single-lead ECG recorders have proved to be feasible for atrial fibrillation mass screening. Even so, they called for more data on the optimal mode and duration of ECG recording.

"In order to relieve both patients and society from the consequences of untreated atrial fibrillation, we believe and hope that atrial fibrillation screening in risk groups will be a part of the standard healthcare in many countries in the near future," according to the editorialists.

"Besides, isn't it encouraging that we can use our smartphones to search for other things than Pokémons?"