Mass spectrometry based analytical quality assessment of serum and plasma specimens with patterns of endo- and exogenous peptides.

Background Inappropriate preanalytical sample handling is a major threat for any biomarker discovery approach. Blood specimens have a genuine proteolytic activity that leads to a time dependent decay of peptidic quality control markers (QCMs). The aim of this study was to identify QCMs for direct assessment of sample quality (DASQ) of serum and plasma specimens. Methods Serum and plasma specimens of healthy volunteers and tumor patients were spiked with two synthetic reporter peptides (exogenous QCMs) and aged under controlled conditions for up to 24 h. The proteolytic fragments of endogenous and exogenous QCMs were monitored for each time point by mass spectrometry (MS). The decay pattern of peptides was used for supervised classification of samples according to their respective preanalytical quality. Results The classification accuracy for fresh specimens (1 h) was 96% and 99% for serum and plasma specimens, respectively, when endo- and exogenous QCMs were used for the calculations. However, classification of older specimens was more difficult and overall classification accuracy decreased to 79%. Conclusions MALDI-TOF MS is a simple and robust method that can be used for DASQ of serum and plasma specimens in a high throughput manner. We propose DASQ as a fast and simple step that can be included in multicentric large-scale projects to ensure the homogeneity of sample quality.