Enhancing Newborn Screening for Tyrosinemia Type I

Evaluation of Neonatal Screening Programs for Tyrosinemia Type 1 Worldwide

In The Netherlands, newborn screening (NBS) for tyrosinemia type 1 (TT1) uses dried blood spot (DBS) succinylacetone (SUAC) as a biomarker. However, high false-positive (FP) rates and a false-negative (FN) case show that the Dutch TT1 NBS protocol is suboptimal. In search of optimization options, we evaluated the protocols used by other NBS programs and their performance. We distributed an online survey to NBS program representatives worldwide (N = 41). Questions focused on the organization and performance of the programs and on changes since implementation. Thirty-three representatives completed the survey. TT1 incidence ranged from 1/13,636 to 1/750,000. Most NBS samples are taken between 36 and 72 h after birth. Most used biomarkers were DBS SUAC (78.9%), DBS Tyrosine (Tyr; 5.3%), or DBS Tyr with second tier SUAC (15.8%). The pooled median cut-off for SUAC was 1.50 µmol/L (range 0.3-7.0 µmol/L). The median cut-off from programs using laboratory-developed tests was significantly higher (2.63 µmol/L) than the medians from programs using commercial kits (range 1.0-1.7 µmol/L). The pooled median cut-off for Tyr was 216 µmol/L (range 120-600 µmol/L). Overall positive predictive values were 27.3% for SUAC, 1.2% for Tyr solely, and 90.1% for Tyr + SUAC. One FN result was reported for TT1 NBS using SUAC, while three FN results were reported for TT1 NBS using Tyr. The NBS programs for TT1 vary worldwide in terms of analytical methods, biochemical markers, and cut-off values. There is room for improvement through method standardization, cut-off adaptation, and integration of new biomarkers. Further enhancement is likely to be achieved by the application of post-analytical tools.

Diagnosis and the importance of early treatment of tyrosinemia type 1: A case report

Tyrosinemia type 1 is an autosomal recessive aminoacidopathy caused by fumarylacetoacetate hydrolase (FAH) deficiency. Consequently, tyrosine and its metabolites accumulate, resulting in liver and kidney toxicity. Symptoms of the disease usually manifest after three weeks of life and include vomiting, failure to thrive, hepatomegaly, jaundice, bleeding diathesis, rickets and renal tubular dysfunction. Untreated, the disease eventually progresses to liver or kidney failure and generally results in a fatal outcome. Expedient diagnosis is critical because an early start of treatment can increase the likelihood of a positive outcome. Here, we report on a male newborn with a family history positive for tyrosinemia type 1 who was subjected to a metabolic work-up immediately after birth. Amino acids were quantified by tandem mass spectrometry coupled with ultra performance liquid chromatography. Urinary organic acids were analyzed on capillary gas chromatography coupled with mass spectrometry. DNA analysis of the FAH gene was performed by Sanger sequencing. On the first day of life, the patient's plasma amino acids showed an increased tyrosine concentration, while urine organic acids detected succinylacetone, a tyrosine metabolite specific for tyrosinemia type 1. The patient's DNA analysis revealed homozygosity of the c.554-1G > T mutation in the FAH gene, which was consistent with the diagnosis. Nitisinone treatment, combined with a dietary restriction of tyrosine and phenylalanine, was introduced immediately. Regular visits and measurement of amino acid concentrations, which enables therapy adjustment and treatment efficiency monitoring in patients with tyrosinemia type 1, has continued over the past 4+ years, and is expected to continue.

A Rapid Screening Test on Dried Blood for the Neonatal Diagnosis of Tyrosinemia Type I

BACKGROUND

Tyrosinemia is an inherited metabolic disorder characterized by elevated levels of tyrosine and its metabolites in plasma. Without treatment, the disease will progress to hepatic and renal failure, so that without liver transplantation will cause death in less than 10 years of age. So, early diagnosis and treatment can be life saving and crucial. It means that with early treatment starting in the neonatal period, the patient can have normal life with very few restrictions in diets containing tyrosine and phenylalanine.

OBJECTIVES

In this study we wanted to evaluate an easy to perform, rapid and sensitive qualitative test with low cost, as a part of neonatal screening tests to help early diagnosis and treatment of hereditary tyrosinemia.

PATIENTS AND METHODS

In this cross sectional study, during the study period (2013 - 2014), 100 patients were selected. Fifty three (53) of these patients had proven tyrosinemia and the other 47 cases biliary atresia, paucity of intrahepatic bile ducts, cytomegalovirus (CMV) hepatitis, galactosemia and storage diseases.

RESULTS

There were 2 false negative and 14 false positive cases of hereditary tyrosinemia (HT-1) in the test. Six cases of biliary atresia, 7 cases of paucity of intrahepatic bile ducts and one patient with cytomegalovirus (CMV) hepatitis were falsely positive with the test. Sensitivity of the test was 96.23%, specificity 71.43%, positive predictive value (PPV) 78.46%, and negative predictive value (NPV) 94.59%.

CONCLUSIONS

This rapid qualitative test on dried blood sample is an easy, cheap, and feasible method for the screening of hereditary tyrosinemia in neonatal period.