QT/QTc prolongation in placebo-treated subjects: a PhRMA collaborative data analysis.

In an ongoing effort to try to understand the variability of QT/QTc data and determine how that variability would affect the design, analysis, and conclusions drawn from data collected in thorough QT/QTc studies, five Pharmaceutical Research and Manufacturers Association (PhRMA) companies recently performed retrospective analyses of placebo and nondrug 12-lead resting electrocardiogram (ECG) data. The data were obtained from five rigorously conducted studies in which the collection and analysis of QT/QTc intervals was a primary objective. Variables that are known to affect variability of QT/QTc intervals, such as adequate resting time before recording the ECGs, food, and consistency of lead placement, had been well controlled in each of the studies. Single ECGs were recorded at each time point, and the QT intervals were measured by ECG laboratories.