Fig. 4.

Flowchart of the methodological strategy for the screening of inborn errors of metabolism. Blood from a prick on the heel of the newborn is collected on dried blood spot (DBS; second-third day of life). This method lets the biological sample be chemically more stable, simplifying delivery modes and allowing easy and long-term sample conservation. Metabolites are extracted and eluted from the DBS, and suitably prepared for mass spectrometry analysis. The use of neutral loss, precursor ion scan, and multiple reaction monitoring experiments allows quantifying metabolites which are biomarkers of specific inborn errors of metabolism.