NT-proBNP Levels
In the LOOP Study, whole-blood samples were taken from study participants at the local centers upon randomization. NT-proBNP levels were measured in 2 central hospital laboratories with the sandwich electrochemiluminescence immunoassay (Roche Diagnostics GmbH, Germany) and the Cobas 8000 analyzer system (Roche Diagnostics) in accordance with manufacturer instructions.In the present study, we included the participants with available NT-proBNP measurement at baseline and further divided them into 2 subgroups based on the median NT-proBNP level, which was also identical to the clinically reasonable cutoff for AF screening, as previously proposed and currently used in ongoing trials.