What are the key criteria for selecting stable isotope-labeled standards for clinical measurements?

What are the key criteria for selecting stable isotope-labeled standards for clinical measurements?

These exogenous compounds must be structurally unique (within a given sample type) and similar (to the native target, from a physicochemical standpoint) as well as resolvable by MS (≥3 Da generally preferred), free from H/D exchange (if D standards are employed), and ideally co-elute (with their native target).