Which MS technique is commonly employed for IEM screening?

• A. MALDI-ToF MS
• B. GC-MS
• C. HPLC-MS
• D. Tandem MS/MS

Answer: (D)

The main idea here is the need for rapid, highly specific, multiplexed measurement of many metabolites from a tiny sample. Tandem mass spectrometry fits that need perfectly because it uses two mass analyzers with a collision-induced fragmentation step in between. This setup lets you select a specific precursor ion, break it into fragments, and then detect a characteristic product ion. The result is high specificity in a complex biological mix and the ability to monitor many metabolite targets in one run (a technique known as multiple reaction monitoring). That combination—speed, sensitivity, and multiplex capability—makes it the workhorse for newborn screening panels that quantify amino acids and acylcarnitines to flag inborn errors of metabolism.

Other MS approaches don’t offer the same combination. MALDI-ToF is excellent for identifying proteins, peptides, or microorganisms, not for rapid, targeted, multi-analyte quantitation in dried blood spots. GC-MS can measure many small molecules but usually requires more sample preparation and longer run times, making it less practical for widespread initial screening. LC-MS without tandem MS lacks the selective, multiple-analyte detection that tandem MS provides.