Newborn screening for hepatorenal tyrosinemia: Tandem mass spectrometric quantification of succinylacetone

Abstract

Background: False-positive and false-negative results occur in current newborn-screening programs for hepatorenal tyrosinemia, which measure tyrosine concentrations in blood spots, sometimes in combination with other metabolites, including succinylacetone. We present our experience with a newly described method for succinylacetone quantification in routine newborn screening. Methods: Succinylacetone was extracted from blood spots that had already been extracted with absolute methanol for acylcarnitine and amino acid analysis. The solvent was acetonitrile-water (80:20 by volume) containing formic acid, hydrazine hydrate, and 100 nmol/L 5,7-dioxooctanoic acid as internal standard: Analysis was performed by tandem mass spectrometry in a separate run. Results: Of 61 344 samples, 99.6% had succinylacetone concentrations ≤5 μmol/L. With a cutoff of 10 μmol/L, no false-positive results were obtained. In 2 patients, the succinylacetone concentrations in the dried blood spots from the 36th and 56th hours of life were 152 and 271 μmol/L, respectively, and the tyrosine concentrations were 54 and 129 μmol/L. Hepatorenal tyrosinemia was subsequently confirmed in both patients. Retrospective analysis of the neonatal screening samples of 2 additional known patients revealed increased succinylacetone concentrations of 46 and 169 μmol/L, respectively. Conclusions: Tandem mass spectrometric quantification directly from residual blood spots is a useful method for the early detection of hepatorenal tyrosinemia in newborn-screening programs. © 2006 American Association for Clinical Chemistry.