QMDB data details

Are the metabolite concentrations displayed normalized? Would it be possible to get unnormalized data?

The data within the QMDB has been normalized to internal quality control samples on every plate. This is necessary to make the measurements obtained at different laboratories comparable. Without this standardization, calculating reference ranges would not make sense.

Why do I have to download every calculated table sequentially?

Including several calculated metabolite concentration range tables in a single file cannot be offered due to technical limitations. The calculation and export file format is the same for all export formats offered, and most of the export formats provided do not support several tabs within one downloaded file.

Why is there an option to log-transform the concentration ranges in the export?

Not the concentration ranges are log transformed, but the ranges are calculated from log transformed concentrations. The means and standard deviation from log transformed concentrations can be used for statistics. Many statistical methods require the data to follow a normal distribution, which is not the case for metabolomic data. After log transformation, the concentrations do follow a normal distribution and using parametric statistical methods thus becomes valid.