Method Description

In the United States, every newborn undergoes state-mandated screening on the second day of life or before leaving the hospital. Blood from a heel prick is dripped onto a filter paper card. The blood is left to dry before sending the filter paper card along with pertinent demographic information to the screening laboratory.

Blood for the supplemental newborn screening is collected in the same way and then sent to the Biochemical Genetics Laboratory, after obtaining parental consent. A 1/8-inch (3-mm) disk is punched out of the blood spot onto 96-well plate. Then, the amino acids and acylcarnitines are extracted by the addition of methanol and known concentrations of isotopically labeled amino acids and acylcarnitines as internal standards. The extract is moved to another 96-well plate, dried under a stream of nitrogen, and derivatized by the addition of n-butanol hydrochloric acid. In a parallel process, succinylacetone is extracted from the residual blood spot, derivatized with an acidic hydrazine solution, evaporated and combined with the amino acid and acylcarnitine extract amino acids and acylcarnitines are measured as their butyl esters with the hydrazone derivative of succinylacetone by electrospray tandem mass spectrometry. The concentrations of the analytes are established by computerized comparison of ion intensities of these analytes to that of the respective internal standards.(Turgeon C, Magera MJ, Allard P, et al. Combined newborns screening for succinylacetone, amino acids, and acylcarnitines in dried blood spots. Clin Chem. 2008;54[4]:657-664; Gavrilov DK, Piazza AL, Pino G, et al. The combined impact of CLIR post-analytical tools and second tier testing on the performance of newborn screening for disorders of propionate, methionine, and cobalamin metabolism. Int J Neonatal Screen. 2020;6[2]:33)