Laboratory evaluation of infants with isolated elevation of propionylcarnitine (C3) on newborn screening

Cr: creatine; CBC: complete blood count; UA: urinalysis; SUCLA2: succinate-CoA ligase ADP-forming beta subunit; Cbl: cobalamin; TCN: transcobalamin; TCR: transcobalamin receptor.
* Ammonia should be drawn free flowing (without tourniquet), placed immediately on ice, and processed STAT to avoid false-positive elevation.
¶ Plasma acylcarnitine profile may show elevated C4-dicarboxylic acylcarnitine (C4DC); a marker for both methylmalonylcarnitine and succinylcarnitine.
Δ Other findings in propionic acidemia include presence of methylcitrate, tiglylglycine, propionylglycine, and lactic acid on urine organic acids; elevated glycine on plasma amino acids. Usually, hyperammonemia is more severe in propionic acidemia compared with methylmalonic acidemia.