Decoding hepatorenal tyrosinemia type 1: Unraveling the impact of early detection, NTBC, and the role of liver transplantation.

Hepatorenal tyrosinemia type 1 (HT-1) is a rare autosomal recessive disease that results from a deficiency of fumaryl acetoacetate hydrolase (FAH), a critical enzyme in the catabolic pathway for tyrosine. This leads to the accumulation of toxic metabolites such as fumaryl and maleylacetoacetate, which can damage the liver, kidneys, and nervous system. The discovery of 2-[2-nitro-4-trifluoromethylbenzoyl]-1,3-cyclohexanedione (NTBC or nitisinone) has significantly improved the management of HT-1, particularly when initiated before the onset of symptoms. Therefore, newborn screening for HT-1 is essential for timely diagnosis and prompt treatment. The analysis of succinyl acetone (SA) in dried blood spots of newborns followed by quantification of SA in blood or urine for high-risk neonates has excellent sensitivity and specificity for the diagnosis of HT-1. NTBC combined with dietary therapy, if initiated early, can provide liver transplant (LT) free survival and reduce the risk of hepatocellular carcinoma (HCC). Patients failing medical treatment (eg, due to non-adherence), and who develop acute liver failure (ALF), have HCC or evidence of histologically proven dysplastic liver nodule(s), or experience poor quality of life secondary to severe dietary restrictions are currently indicated for LT. Children with HT-1 require frequent monitoring of liver and renal function to assess disease progression and treatment compliance. They are also at risk of long-term neurocognitive impairment, which highlights the need for neurocognitive assessment and therapy.

Assessing the quality and value of metabolic chart data for capturing core outcomes for pediatric medium-chain acyl-CoA dehydrogenase (MCAD) deficiency.

BACKGROUND: Generating rigorous evidence to inform care for rare diseases requires reliable, sustainable, and longitudinal measurement of priority outcomes. Having developed a core outcome set for pediatric medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, we aimed to assess the feasibility of prospective measurement of these core outcomes during routine metabolic clinic visits. METHODS: We used existing cohort data abstracted from charts of 124 children diagnosed with MCAD deficiency who participated in a Canadian study which collected data from birth to a maximum of 11 years of age to investigate the frequency of clinic visits and quality of metabolic chart data for selected outcomes. We recorded all opportunities to collect outcomes from the medical chart as a function of visit rate to the metabolic clinic, by treatment centre and by child age. We applied a data quality framework to evaluate data based on completeness, conformance, and plausibility for four core MCAD outcomes: emergency department use, fasting time, metabolic decompensation, and death. RESULTS: The frequency of metabolic clinic visits decreased with increasing age, from a rate of 2.8 visits per child per year (95% confidence interval, 2.3-3.3) among infants 2 to 6 months, to 1.0 visit per child per year (95% confidence interval, 0.9-1.2) among those ≥ 5 years of age. Rates of emergency department visits followed anticipated trends by child age. Supplemental findings suggested that some emergency visits occur outside of the metabolic care treatment centre but are not captured. Recommended fasting times were updated relatively infrequently in patients' metabolic charts. Episodes of metabolic decompensation were identifiable but required an operational definition based on acute manifestations most commonly recorded in the metabolic chart. Deaths occurred rarely in these patients and quality of mortality data was not evaluated. CONCLUSIONS: Opportunities to record core outcomes at the metabolic clinic occur at least annually for children with MCAD deficiency. Methods to comprehensively capture emergency care received at outside institutions are needed. To reduce substantial heterogeneous recording of core outcome across treatment centres, improved documentation standards are required for recording of recommended fasting times and a consensus definition for metabolic decompensations needs to be developed and implemented.

Intrauterine enzyme replacement therapies for lysosomal storage disorders: Current developments and promising future prospects.

Lysosomal storage disorders (LSDs) are a group of monogenic condition, with many characterized by an enzyme deficiency leading to the accumulation of an undegraded substrate within the lysosomes. For those LSDs, postnatal enzyme replacement therapy (ERT) represents the standard of care, but this treatment has limitations when administered only postnatally because, at that point, prenatal disease sequelae may be irreversible. Furthermore, most forms of ERT, specifically those administered systemically, are currently unable to access certain tissues, such as the central nervous system (CNS), and furthermore, may initiate an immune response. In utero enzyme replacement therapy (IUERT) is a novel approach to address these challenges evaluated in a first-in-human clinical trial for IUERT in LSDs (NCT04532047). IUERT has numerous advantages: in-utero intervention may prevent early pathology; the CNS can be accessed before the blood-brain barrier forms; and the unique fetal immune system enables exposure to new proteins with the potential to prevent an immune response and may induce sustained tolerance. However, there are challenges and limitations for any fetal procedure that involves two patients. This article reviews the current state of IUERT for LSDs, including its advantages, limitations, and potential future directions for definitive therapies.

Case report: A case of spinal muscular atrophy in a preterm infant: risks and benefits of treatment.

Spinal muscular atrophy (SMA) is a neuromuscular genetic disorder caused by the loss of lower motor neurons leading to progressive muscle weakness and atrophy. With the rise of novel therapies and early diagnosis on newborn screening (NBS), the natural history of SMA has been evolving. Earlier therapeutic interventions can modify disease outcomes and improve survival. The role of treatment in infants born preterm is an important question given the importance of early intervention. In this study, we discuss the case of an infant born at 32 weeks who was diagnosed with SMA on NBS and was treated with Spinraza® (Nusinersen) and Zolgensma® (Onasemnogene abeparvovec-xioi) within the first 2 months of life. With the scarce evidence that currently exists, clinicians should be aware of the efficacy and safety impact of early therapy particularly in the preterm infant.

The Ontario Newborn Screening Program: A novel referral center model.

Newborn screening (NBS) for inherited and congenital disorders is a form of secondary disease prevention and a public health responsibility. The development of NBS programs is one of the most important achievements in health care. While the scope of the screening targets has expanded and methods have evolved, the screening process has remained essentially unchanged.In 2006, the Canadian province of Ontario implemented a new provincial NBS program that differs from conventional programs. One of the key differences is the structured and fully funded partnership between the ministry of health, the NBS laboratory, and the treatment centers in the province. Each one of these partners has defined roles and accountability. Another difference is the move away from the conventional recall process to an immediate referral system to selected treatment centers.In this article, we report our experience with the new screening structure and discuss it as a model for future NBS programs.

The mitochondrial tRNA MT-TW m.5537_5538insT variant presents with significant intra-familial clinical variability.

Mitochondrial disorders can present with a wide range of clinical and biochemical phenotypes. Mitochondrial DNA variants may be influenced by factors such as degree of heteroplasmy and tissue distribution. We present a four-generation family in which 10 individuals carry a pathogenic mitochondrial variant (m.5537_5538insT, MT-TW gene) with differing levels of heteroplasmy and clinical features. This genetic variant has been documented in two prior reports, both in individuals with Leigh syndrome. In the current family, three individuals have severe mitochondrial symptoms including Leigh syndrome (patient 1, 100% in blood), MELAS (patient 2, 97% heteroplasmy in muscle), and MELAS-like syndrome (patient 3, 50% heteroplasmy in blood and 100% in urine). Two individuals have mild mitochondrial symptoms (patient 4, 50% in blood and 67% in urine and patient 5, 50% heteroplasmy in blood and 30% in urine). We observe that this variant is associated with multiple mitochondrial presentations and phenotypes, including MELAS syndrome for which this variant has not previously been reported. We also demonstrate that the level of heteroplasmy of the mitochondrial DNA variant correlates with the severity of clinical presentation; however, not with the specific mitochondrial syndrome.

Parental Preferences for Expanded Newborn Screening: What Are the Limits?

The use of next-generation sequencing technologies such as genomic sequencing in newborn screening (NBS) could enable the detection of a broader range of conditions. We explored parental preferences and attitudes towards screening for conditions for which varying types of treatment exist with a cross-sectional survey completed by 100 parents of newborns who received NBS in Ontario, Canada. The survey included four vignettes illustrative of hypothetical screening targets, followed by questions assessing parental attitudes. Chi-square tests were used to compare frequency distributions of preferences. Results show that most parents supported NBS for conditions for which only supportive interventions are available, but to a significantly lesser degree than those with disease-specific treatments (99% vs. 82-87%, p ≤ 0.01). For conditions without an effective treatment, the type of supportive care and age of onset of the condition did not significantly alter parent perceptions of risks and benefits. Parents are interested in expanded NBS for conditions with only supportive interventions in childhood, despite lower levels of perceived benefit for the child and greater anticipated anxiety from screen-positive results. These preferences suggest that the expansion of NBS may require ongoing deliberation of perceived benefits and risks and enhanced approaches to education, consent, and support.

Estimating the Incidence of First RSV Hospitalization in Children Born in Ontario, Canada.

BACKGROUND: Respiratory syncytial virus (RSV) contributes significantly to morbidity in children, placing substantial burdens on health systems, thus RSV vaccine development and program implementation are a public health priority. More data on burden are needed by policymakers to identify priority populations and formulate prevention strategies as vaccines are developed and licensed. METHODS: Using health administrative data, we calculated incidence rates of RSV hospitalization in a population-based birth cohort of all children born over a six-year period (May 2009 to June 2015) in Ontario, Canada. Children were followed until their first RSV hospitalization, death, 5th birthday, or the end of the study period (June 2016). RSV hospitalizations were identified using a validated algorithm based on International Classification of Diseases, 10th Revision, and/or laboratory-confirmed outcomes. We calculated hospitalization rates by various characteristics of interest, including calendar month, age groups, sex, comorbidities, and gestational age. RESULTS: The overall RSV hospitalization rate for children <5 years was 4.2 per 1000 person-years (PY) with a wide range across age groups (from 29.6 to 0.52 per 1000 PY in children aged 1 month and 36-59 months, respectively). Rates were higher in children born at a younger gestational age (23.2 per 1000 PY for those born at <28 weeks versus 3.9 per 1000 PY born at ≥37 weeks); this increased risk persisted as age increased. While the majority of children in our study had no comorbidities, rates were higher in children with comorbidities. For all age groups, rates were highest between December and March. CONCLUSIONS: Our results confirm the high burden of RSV hospitalization and highlight young infants are at additional risk, namely premature infants. These results can inform prevention efforts.

TRNT-1 Deficiency Is Associated with Loss of tRNA Integrity and Imbalance of Distinct Proteins.

Mitochondrial diseases are a group of heterogeneous disorders caused by dysfunctional mitochondria. Interestingly, a large proportion of mitochondrial diseases are caused by defects in genes associated with tRNA metabolism. We recently discovered that partial loss-of-function mutations in tRNA Nucleotidyl Transferase 1 (TRNT1), the nuclear gene encoding the CCA-adding enzyme essential for modifying both nuclear and mitochondrial tRNAs, causes a multisystemic and clinically heterogenous disease termed SIFD (sideroblastic anemia with B-cell immunodeficiency, periodic fevers, and developmental delay; SIFD). However, it is not clear how mutations in a general and essential protein like TRNT1 cause disease with such clinically broad but unique symptomatology and tissue involvement. Using biochemical, cell, and mass spectrometry approaches, we demonstrate that TRNT1 deficiency is associated with sensitivity to oxidative stress, which is due to exacerbated, angiogenin-dependent cleavage of tRNAs. Furthermore, reduced levels of TRNT1 lead to phosphorylation of Eukaryotic Translation Initiation Factor 2 Subunit Alpha (eIF2α), increased reactive oxygen species (ROS) production, and changes in the abundance of distinct proteins. Our data suggest that the observed variable SIFD phenotypes are likely due to dysregulation of tRNA maturation and abundance, which in turn negatively affects the translation of distinct proteins.

Newborn Screening Conditions: Early Intervention and Probability of Developmental Delay.

OBJECTIVES: The purpose of this study is to explore which newborn screening (NBS) conditions are automatically eligible for early intervention (EI) across states and to determine the extent to which each disorder should automatically qualify for EI because of a high probability of developmental delay. METHODS: We examined each state's EI eligibility policy and reviewed the literature documenting developmental outcomes for each NBS condition. Using a novel matrix, we assessed the risk of developmental delay, medical complexity, and risk of episodic decompensation, revising the matrix iteratively until reaching consensus. Three NBS conditions (biotinidase deficiency, severe combined immunodeficiency, and propionic acidemia) are presented in detail as examples. RESULTS: Most states (88%) had Established Conditions lists to autoqualify children to EI. The average number of NBS conditions listed was 7.8 (range 0-34). Each condition appeared on average in 11.7 Established Conditions lists (range 2-29). After the literature review and consensus process, 29 conditions were likely to meet national criteria for an Established Condition. CONCLUSION: Despite benefiting from NBS and timely treatment, many children diagnosed with NBS conditions are at risk for developmental delays and significant medical complexity. The results demonstrate a need for more clarity and guidance regarding which children should qualify for EI. We suggest that most NBS conditions should automatically qualify based on the probability of resulting in a developmental delay. These findings suggest a future opportunity for collaboration between NBS and EI programs to create a consistent set of Established Conditions, potentially expediate referrals of eligible children, and streamline children's access to EI services.

Ethical and practical considerations related to data sharing when collecting patient-reported outcomes in care-based child health research.

PURPOSE: The collection and use of patient reported outcomes (PROs) in care-based child health research raises challenging ethical and logistical questions. This paper offers an analysis of two questions related to PROs in child health research: (1) Is it ethically obligatory, desirable or preferable to share PRO data collected for research with children, families, and health care providers? And if so, (2) What are the characteristics of a model best suited to guide the collection, monitoring, and sharing of these data? METHODS: A multidisciplinary team of researchers, providers, patient and family partners, and ethicists examined the literature and identified a need for focus on PRO sharing in pediatric care-based research. We constructed and analyzed three models for managing pediatric PRO data in care-based research, drawing on ethical principles, logistics, and opportunities to engage with children and families. RESULTS: We argue that it is preferable to share pediatric PRO data with providers, but to manage expectations and balance the risks and benefits of research, this requires a justifiable data sharing model. We argue that a successful PRO data sharing model will allow children and families to have access to and control over their own PRO data and be engaged in decision-making around how PROs collected for research may be integrated into care, but require support from providers. CONCLUSION: We propose a PRO data sharing model that can be used across diverse research settings and contributes to improved transparency, communication, and patient-centered care and research.

Variability in Newborn Screening Across Canada: Spinal Muscular Atrophy and Beyond.

BACKGROUND: Newborn screening (NBS) identifies infants with severe, early-onset diseases, enabling early diagnosis and treatment. In Canada, decisions regarding disease inclusion in NBS programs occur at the provincial level, which leads to variability in patient care. We aimed to determine whether important differences exist in NBS programs across provinces and territories. Given that spinal muscular atrophy (SMA) is the most recent disease added to NBS programs, we hypothesized that its inclusion would show interprovincial variability and be more likely in provinces already screening for a greater number of diseases. METHODS: We conducted a cross-sectional survey of all NBS labs in Canada to understand: 1) what conditions were included in their program; 2) what genetic-based testing was performed and; 3) if SMA was included. RESULTS: All NBS programs (N = 8) responded to this survey by June 2022. There was a 2.5-fold difference in the number of conditions screened (N = 14 vs N = 36) and a 9-fold difference in the number of conditions screened by gene-based testing. Only nine conditions were common to all provincial NBS programs. NBS for SMA was performed in four provinces at the time of our survey, with BC recently becoming the fifth province to add SMA to their NBS on October 1, 2022. Currently, 72% of Canadian newborns are screened for SMA at birth. CONCLUSION: Although healthcare in Canada is universal, its decentralization gives rise to regional differences in NBS programs which creates inequity in the treatment, care, and potential outcomes of affected children across provincial jurisdictions.

Development and external validation of machine learning algorithms for postnatal gestational age estimation using clinical data and metabolomic markers.

BACKGROUND: Accurate estimates of gestational age (GA) at birth are important for preterm birth surveillance but can be challenging to obtain in low income countries. Our objective was to develop machine learning models to accurately estimate GA shortly after birth using clinical and metabolomic data. METHODS: We derived three GA estimation models using ELASTIC NET multivariable linear regression using metabolomic markers from heel-prick blood samples and clinical data from a retrospective cohort of newborns from Ontario, Canada. We conducted internal model validation in an independent cohort of Ontario newborns, and external validation in heel prick and cord blood sample data collected from newborns from prospective birth cohorts in Lusaka, Zambia and Matlab, Bangladesh. Model performance was measured by comparing model-derived estimates of GA to reference estimates from early pregnancy ultrasound. RESULTS: Samples were collected from 311 newborns from Zambia and 1176 from Bangladesh. The best-performing model accurately estimated GA within about 6 days of ultrasound estimates in both cohorts when applied to heel prick data (MAE 0.79 weeks (95% CI 0.69, 0.90) for Zambia; 0.81 weeks (0.75, 0.86) for Bangladesh), and within about 7 days when applied to cord blood data (1.02 weeks (0.90, 1.15) for Zambia; 0.95 weeks (0.90, 0.99) for Bangladesh). CONCLUSIONS: Algorithms developed in Canada provided accurate estimates of GA when applied to external cohorts from Zambia and Bangladesh. Model performance was superior in heel prick data as compared to cord blood data.

An Approach for Evaluating Potential Screening Thresholds Using Biomarker Population Distribution and Analytical Imprecision.

BACKGROUND: A common approach in laboratory medicine is to use a simple but sensitive test to screen samples to identify those that require additional investigation with a more complex and informative method. Selection of screening thresholds can be guided by biomarker distribution in the tested population and the analytical imprecision of the method. METHODS: A simulation using joint probabilities derived from the population distribution for galactose-1-phosphate uridylyltransferase (GALT) activity and the analytical imprecision for the GALT assay was used to estimate the number of samples that would require repeat analysis and the number of samples with possibly false-negative screening determinations due to analytical imprecision. RESULTS: In the case of GALT activity, screening a conservative initial threshold 6 standard deviations from the confirmation threshold can essentially eliminate the chance of a false-negative screening determination due to analytical imprecision. The trade-off is a greater number of samples requiring follow-up testing (n = 222, equivalent to 0.15% of samples annually). CONCLUSIONS: Selection of thresholds in a screening algorithm is informed by estimates of the number of samples that would require repeat testing and the number that could be false negative due to analytical imprecision.

Biotinidase activity is affected by both seasonal temperature and filter collection cards.

This study set out to examine pre-analytical factors affecting the frequency of positive results in newborn screening for biotinidase deficiency. This investigation was prompted by an increase in the annual screen positive rate for biotinidase deficiency in Ontario from 2.65x10-4 in 2016 to 6.57x10-4 in 2017. Season and trend decomposition was used to separate seasonality from an underlying trend in the time series of biotindase activity measurements for the period 2014-01-12 to 2019-07-27 (n = 798,770). This analysis revealed a marked seasonal effect (winter = median + ⩽ 17 MRU, summer = mean - ⩽20 MRU) and a non-linear negative trend. Seasonal temperature was correlated with biotinidase results (Pearson's r = 0.79) but not with the observed negative trend (Pearson's r = 0.0025). Time series analysis of biotinidase results grouped by print lot of filter paper revealed that recently printed filter paper cards inhibit biotinidase and that this inhibition resolved over time. This study demonstrates that biotindase activity is inhibited by both increased seasonal temperature and collection on newly printed filter cards.

Validation of gestational age determination from ultrasound or a metabolic gestational age algorithm using exact date of conception in a cohort of newborns conceived using assisted reproduction technologies.

BACKGROUND: Accurate estimates of gestational age in pregnancy are important for the provision of optimal care. Although current guidelines generally recommend estimating gestational age via first-trimester ultrasound measurement of crown-rump length, error associated with this method can range from 3 to 8 days of gestation. In pregnancies resulting from assisted reproductive technology, estimated due date can be calculated on the basis of the age of the embryo and the date of embryo transfer, arguably providing the most accurate estimates possible. We have developed and extensively validated statistical models to estimate gestational age postnatally using metabolomic markers from blood samples in combination with clinical and demographic data. These models have shown high accuracy compared with first-trimester ultrasound, the recommended method for estimating gestational age in spontaneous pregnancies. We hypothesized that gestational age derived from date and stage of embryo at transfer in newborns conceived using assisted reproduction therapy would provide the most accurate reference standard possible to evaluate and compare the accuracy of both first-trimester ultrasound and metabolomic model-based gestational dating. OBJECTIVE: This study aimed to validate both first-trimester ultrasound dating and postnatal metabolomic gestational age estimation models against gestational age derived from date and stage of embryo at transfer in a cohort of newborns conceived via assisted reproductive technology, both overall and in important subgroups of interest (preterm birth, small for gestational age, and multiple birth). STUDY DESIGN: This was a retrospective cohort study of infants born in Ontario, Canada between 2015 and 2017 and captured in the provincial birth registry. Spontaneous conceptions were randomly partitioned into a model derivation sample (80%) and a test sample (20%) for model validation. A cohort of assisted conceptions resulting from fresh embryo transfers was derived to evaluate the accuracy of both ultrasound and model-based gestational dating. Postnatal gestational age estimation models were developed with multivariable linear regression using elastic-net regularization. Gestational age estimates from dating ultrasound and from postnatal metabolomic models were compared with date of embryo transfer reference gestational age in the independent test cohorts. Accuracy was quantified by calculating mean absolute error and the square root of mean squared error. RESULTS: Our model derivation cohort included 202,300 spontaneous conceptions, and the testing cohorts included 50,735 spontaneous conceptions and 1924 assisted conceptions. In the assisted conception cohort, first-trimester dating ultrasound was accurate to within approximately ±1.5 days compared with date of embryo transfer reference overall (mean absolute error, 0.21 [95% confidence interval, 0.20-0.23]). When compared with gestational age derived from date of embryo transfer, the metabolomic estimation models were accurate to within approximately ±5 days overall (0.79 [0.76-0.81] weeks). When ultrasound was used as the reference in validating the metabolomic model, the mean absolute error was slightly higher overall (0.81 [0.78-0.84] weeks). In general, the accuracy of gestational age estimates derived from ultrasound or metabolomic models was highest in term infants and lower in preterm and small-for-gestational-age newborns. CONCLUSION: Our findings support the accuracy of ultrasound as a gestational age dating tool. They also support the potential utility of metabolic gestational age dating algorithms in settings where ultrasound or other accurate methods of estimating gestational age are not available because of lack of infrastructure or specialized training (eg, low-income countries). However, the accuracy of metabolomic model-based dating was generally lower than that of ultrasound.

In Utero Enzyme-Replacement Therapy for Infantile-Onset Pompe's Disease.

Patients with early-onset lysosomal storage diseases are ideal candidates for prenatal therapy because organ damage starts in utero. We report the safety and efficacy results of in utero enzyme-replacement therapy (ERT) in a fetus with CRIM (cross-reactive immunologic material)-negative infantile-onset Pompe's disease. The family history was positive for infantile-onset Pompe's disease with cardiomyopathy in two previously affected deceased siblings. After receiving in utero ERT and standard postnatal therapy, the current patient had normal cardiac and age-appropriate motor function postnatally, was meeting developmental milestones, had normal biomarker levels, and was feeding and growing well at 13 months of age.

Patient Engagement in a Multi-Stakeholder Workshop to Plan the Collection of Patient-Oriented Outcomes for Children with Inherited Metabolic Diseases.

Building on a study to develop core outcome sets for children with rare inherited metabolic diseases, the purpose of this workshop was to inform the design of longitudinal pediatric registries that support registry-based clinical trials. This workshop was co-designed by two patient/family partner investigators and attended by two family advisors who received preparatory training. Patient partners and advisors recommended integrating the collection of registry data into everyday life and highlighted the importance of transparent communication and attention to the issue of integration of patient-reported data into clinical care. We propose a need to explore strategies for engaging patients in post-project knowledge translation.