To determine whether a diagnosis of OTCD can be made in archived blood spots, we evaluated the stability of glutamine over time.
We also measured glutamine in freshly collected plasma samples (n = 36) referred to our laboratory for amino acid analysis and including some from OTCD patients on treatment.
It is doubtful that the incidence of OTCD justifies a separate newborn dried blood spot screen for glutamine with this method.
This is the case even in archived OTCD dried blood spots that initially contained much higher newborn glutamine concentrations.
It is a superior alternative to the use of an amino acid analyzer to monitor OTCD patients on treatment.