This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2018, Subject name: Biochemistry
Best investigation for metabolic disorders is? 
Select and explain. 
A. Western blot, B. Tandem mass spectrometry, C. PCR, D. Gel electrophoresis
B: Tandem mass spectrometry
Answer: B: Tandem mass spectrometry 
Explanation: Most Powerful technique of screening of inborn error of metabolism is Tandem Mass Spectrometer. *TM Spectrometer combines two mass spectrometers. The first one is used to select a single (precursor) mass, which is characteristic of given analyte in the mixture. These selected ions are collided with neutral gas for activation. The second Mass Spectrometer is used to separate the fragment ions according to mass resulting in "MS/MS" or MS2 spectrum. Advantage is that large number of samples can be dealt with in a sho time.. *HPLC is used as a confirmatory test of the primary test by TMS. HPLC has limited capacity, so not a good screening method. * An alternative good screening method is Microfluorometry (MFL).