Statistical analyses were performed using MedCalcTM for Windows, version 14.12.0 (MedCalcTM software, Oostende, Belgium). Levels of agreement between the two techniques were determined using Bland-Altman methodology [6]. Mean differences were computed as indicators of bias and 95% limits of agreement for each comparison [average difference±1.96 standard deviation (SD) of the difference] were used to indicate how far apart measurements by two methods were likely to fall. Two methods can be used interchangeably only if the differ- ences within mean±1.96 SD are not clinically important. False-negative and false-positive rates for the diagnosis of βTT were calculated.