typical error of measurement, reliability, repeated measurement

Introduction: To ensure proper interpretation of the achieved results (particularly in repeated measurement), it is necessary to know the accuracy of the used method (device). To express the accuracy of measurement, it is possible to use the typical error of measurement (TE) that allows for expressing the determined error in the used measuring units. The method of Dual-Energy X-Ray Absorptiometry (DXA) is now frequently used to measure body composition. Even though this method is considered referential, it is not possible to assume that it measures with absolute accuracy. The aim of the study is to verify the accuracy of the DXA method using TE through repeated measurements, performed consecutively. Material and methods: The research was implemented in a group of 63 participants (38 male, 25 female). The average age of male was 22.6±2.9; female were 21.4±2.0 years old. To measure the body composition parameters using the DXA method, we used Hologic QDR Discovery (Hologic, USA). The measured parameters included body mass (BM), fat free mass (FFM), body fat (BF), bone mineral content (BMC), bone mass density (BMD). Results: During the whole-body analysis, the determined TE was: BM at the level of 0.12 kg, BF 0.25 kg and 0.4%, BMC 19.0 g and BMD 0.01g/cm2. The ICC values of repeated measurements ranged from 1.00 to 0.99. Conclusion: We recommend using only such values that exceed the TE value to be demonstrable when interpreting the results of repeated measurements in diagnostic practice.