[Application of succinylacetone levels measurement in the blood and urine in the diagnosis of tyrosinemia type 1].

Objective: To establish the diagnostic method of tyrosinemia type 1 and evaluate its value, the succinylacetone levels in the blood of suspected patients with tyrosinemia were tested by tandem mass spectrometry, and the succinylacetone in the urine was tested by gas chromatography-mass spectrometry.

Method: A total of 190 patients suspected of having tyrosinemia, were tested by tandem mass spectrometry for measurement of the level of succinylacetone in the blood, and detected by gas chromatography-mass spectrometry for measurement of the level of succinylacetone and organic acid in the urine. The method of measuring the level of succinylacetone in blood by tandem mass spectrometry as follows: After the diameter of 3 mm dry blood spots were punched into wells of 96-well plate, 100 µl 80% acetonitrile were added into each well, which contained hydrazine monohydrate and the internal standard of succinylacetone. The supernatant fluid were transferred to another 96-well plate and dried under heated nitrogen, after the plate was incubated for 30 min at 65°C. The residual hydrazine reagent was removed by addition of 100 µl methanol to each well and evaporated under heated nitrogen. The mobile phase (80% acetonitrile) was added to each well and 20 µl samples were tested by tandem mass spectrometry. The diagnostic terms were the clinical manifestation and the high level of succinylacetone in both blood and urine.

Result: Eleven patients were diagnosed as tyrosinemia type 1, with 9 males and 2 females. Their ages ranged from 2 months to 6 years. The succinylacetone levels in the blood of the patients were remarkably increased (7.26-31.09 µmol/L), with an average of (14.2 ± 7.8)µmol/L. Seven patients were tested for the level of succinylacetone in the urine by gas chromatography-mass spectrometry, and 4 were positive and 3 negative. Their tyrosine levels in the blood were 190-543 µmol/L(Normal: 20 - 100 µmol/L), with an average of (327.3 ± 125.8) µmol/L. All the patients presented the symptoms of hepatomegaly. Among them, 9 patients died and 2 patients were improved after treatment.

Conclusion: The higher levels of succinylacetone in the blood or urine is a remarkable evidence for the diagnosis of tyrosinemia type 1. Determination of succinylacetone in the dry blood spots using tandem mass spectrometry was a good method for diagnosis of tyrosinemia type 1. To test succinylacetone in urine by gas chromatography-mass spectrometry may yield a false-negative result for tyrosinemia type 1.