This limitation of measurement techniques needs to be critically examined, considering that most studies report inter-measurement variability as a mean ± SD of either the absolute difference between pairs of repeated measurements in percentage of their mean or as the coefficient of variation, when more than 2 repeated measurements are performed. This means that measurement variability in individual subjects can be as high as the reported mean measurement variability plus its 2 SD. For example, if a technique was found in a group of 100 patients to have variability of 5 ± 7%, it means that in 10 of the 100 patients the variability was outside the 2-SD range (i.e., the technique could result in differences larger than 5 + 2 × 7%—19% or more), simply because of a random measurement error. Thus, it would be a very legitimate question to ask, “What is the magnitude of change that this technique could detect reliably?” In other words, when a technique is reported to be reproducible within 5%, as determined with repeated measurements, it does not automatically mean that it is capable of reliably detecting differences <5%. Conversely, one should very carefully consider the confidence interval associated with the reported variability.