Editor,—I was intrigued by the paper “Prognostic significance of electrical alternans versus signal averaged electrocardiography in predicting the outcome of electrophysiological testing and arrhythmia-free survival” by Armoundaset al.1 In a time of statistics and prediction of important outcome events the reader has to pay much attention to the literature.

The conclusion “T wave alternans was a highly significant predictor of the outcome of electrophysiological testing and arrhythmia-free survival” is wrong; the positive predictive values are very low with very large confidence limits. The conclusion should be “There is a significant association between T wave alternans (TWA) and the outcome of electrophysiological (EP) testing. With single sided tests of significance there was a difference in arrhythmia-free survival for EP negative v EP positive …