Measurement of Succinylacetone Using HPLC-Tandem Mass Spectrometry and Establishment of a Cut-off Value

ABSTRACT

BACKGROUND: Newborn screening of tyrosinemia type 1 is important for identifying infants at risk for developing this disease before life-threatening symptoms occur. It is difficult to differentiate between tyrosinemia type 1 and transient neonatal tyrosinemia (TNT) by analyzing tyrosine alone. Thus, succinylacetone must be analyzed. In this study, we measured succinylacetone in dried blood spot (DBS) by HPLC-tandem mass spectrometry (HPLC-MS/MS) and established cut-off values. METHODS: We used the hydrazine derivatization method to measure succinylacetone in 127 DBSs showing normal results in the newborn screening test and 93 DBSs showing increased tyrosine levels. We established cut-off values using the 99.9th percentile value or median+5 standard deviation value. RESULTS: Succinylacetone levels determined by our method were well-correlated with the results recommended by the Centers for Disease Control and Prevention for proficiency testing (r=0.9968). The succinylacetone levels in normal newborn DBSs were significantly lower than those in DBSs with high tyrosine levels (P < 0.001). The cut-off values were calculated to be 1.3 µM from the results of 127 normal DBS samples and 2.2 µM from 220 DBSs, including in 93 newborns with TNT. CONCLUSIONS: Measurement of succinylacetone in DBSs by HPLC-MS/MS is useful in individuals with increased tyrosine concentrations and can be used for rapid differential diagnosis of tyrosinemia when an appropriate cut-off value is established.