1. Preanalytical phase
In metabolomics, the preanalytical phase of planning, collecting samples and sample preparation is of utmost importance in order to avoid unwanted confounding variance in the resulting spectroscopic data. For a successful project, it is necessary to consider even minute practical considerations:
- Is there a sampling SOP in place, e.g. stating what sampling tube, timing, centrifugation speed, temperature storage, sample transport method etc. should be used?
- If the sampling occurs at different sites, by different people, has any effort in unfying the SOP been done?
A central mantra in planning for a metabolomics project should be 'same, same, same' to ensure that, even though maybe a suboptimal sampling scheme was used, at least a comparison between samples that have had a similar history before ending up in the NMR spectrometer will be sensible.
The project is about the effect of gastric bypass surgery and related medication on diabetic kidney disease (DKD). The samples were urine that were prepared according to the Bruker IVDr SOP for human urine samples, i.e. dilution 9:1 sample:buffer before transfer to SampleJet NMR tube racks. The sample preparation was done with a Bruker SamplePro liquid handling robot (nickname "Sebulba") to minimize human handling error. All sample were kept cool throughout the preparation process and also in the sample changer before going into the spectrometer. Acquisition order was randomized to minimize batch effects.