- QTcF >450 millisecond (msec) QTcF is either machine-read or manually over-read. The specific formula that will be used to determine eligibility and discontinuation for an individual subject should be determined prior to initiation of the study. In other words, several different formulae cannot be used to calculate the corrected QT interval (QTc) for an individual subject and then the lowest QTc value used to include or discontinue the subject from the trial. For purposes of data analysis, QTcF, another QT correction formula, or a composite of available values of QTc will be used