Arguments for early screening: a clinician's perspective

Current and Future Treatments for Classic Galactosemia

Type I (classic) galactosemia, galactose 1-phosphate uridylyltransferase (GALT)-deficiency is a hereditary disorder of galactose metabolism. The current therapeutic standard of care, a galactose-restricted diet, is effective in treating neonatal complications but is inadequate in preventing burdensome complications. The development of several animal models of classic galactosemia that (partly) mimic the biochemical and clinical phenotypes and the resolution of the crystal structure of GALT have provided important insights; however, precise pathophysiology remains to be elucidated. Novel therapeutic approaches currently being explored focus on several of the pathogenic factors that have been described, aiming to (i) restore GALT activity, (ii) influence the cascade of events and (iii) address the clinical picture. This review attempts to provide an overview on the latest advancements in therapy approaches.

Biochemical screening of 504,049 newborns in Denmark, the Faroe Islands and Greenland--experience and development of a routine program for expanded newborn screening

Expanded newborn screening for selected inborn errors of metabolism (IEM) in Denmark, the Faroe Islands and Greenland was introduced in 2002. We now present clinical, biochemical, and statistical results of expanded screening (excluding PKU) of 504,049 newborns during nine years as well as diagnoses and clinical findings in 82,930 unscreened newborns born in the same period. The frequencies of diagnoses made within the panel of disorders screened for are compared with the frequencies of the disorders in the decade preceding expanded newborn screening. The expanded screening was performed as a pilot study during the first seven years, and the experience obtained during these years was used in the development of the routine neonatal screening program introduced in 2009. Methods for screening included tandem mass spectrometry and an assay for determination of biotinidase activity. A total of 310 samples from 504,049 newborns gave positive screening results. Of the 310 results, 114 were true positive, including results from 12 newborns in which the disease in question was subsequently diagnosed in their mothers. Thus, the overall frequency of an IEM in the screening panel was 1:4942 (mothers excluded) or 1:4421 (mothers included). The false positive rate was 0.038% and positive predictive value 37%. Overall specificity was 99.99%. All patients with true positive results were followed in The Center for Inherited Metabolic Disorders in Copenhagen, and the mean follow-up period was 45 months (range 2109 months). There were no deaths among the 102 children, and 94% had no clinically significant sequelae at last follow-up. Our study confirms the higher frequency of selected IEM after implementation of expanded newborn screening and suggests an improved outcome for several disorders. We argue that newborn screening for these disorders should be standard of care, though unresolved issues remain, e.g. about newborns with a potential for remaining asymptomatic throughout life. Well organized logistics of the screening program from screening laboratory to centralized, clinical management is important.

Evaluation and long-term follow-up of infants with inborn errors of metabolism identified in an expanded screening programme

Newborn screening (NBS) by tandem mass spectrometry started in Galicia (Spain) in 2000. We analyse the results of screening and clinical follow-up of inborn errors of metabolism (IEM) detected during 10 years. Our programme basically includes the disorders recommended by the American College of Medical Genetics. Since 2002, blood and urine samples have been collected from every newborn on the 3rd day of life; before then, samples were collected between the 5th and 8th days. Newborns who show abnormal results are referred to the clinical unit for diagnosis and treatment. In these 10 years, NBS has led directly to the identification of 137 IEM cases (one per 2060 newborns, if 35 cases of benign hyperphenylalaninemia are excluded). In addition, 33 false positive results and 10 cases of transitory elevation of biomarkers were identified (making the positive predictive rate 76.11%), and 4 false negative results. The use of urine samples contributed significantly to IEM detection in 44% of cases. Clinical symptoms appeared before positive screening results in nine patients (6.6%), four of them screened between days 5 and 8. The death rate was 2.92%; of the survivors, 95.5% were asymptomatic after a mean observation period of 54 months, and only two had an intellectual/psychomotor development score less than 85. Compared to other studies, a high incidence of type I glutaric aciduria was detected, one in 35,027 newborns. This report highlights the benefits of urine sample collection during screening, and it is the first study on expanded newborn screening results in Spain.

Newborn screening in Canada - Are we out of step?

OBJECTIVES

To review the status of universal newborn screening programs in Canada.

METHODS

A brief questionnaire (seven questions) was circulated to one key individual in each province (n=10) and territory (n=3). These individuals were usually physicians or clinical biochemists closely involved in the diagnosis and treatment of genetic metabolic diseases.

RESULTS

Universal newborn screening is under provincial jurisdiction. The number of diseases screened for varies and ranges from three to 28. Nine provinces/territories have a central computerized system for tracking initially positive cases. Only five provinces/territories have adequate personnel and resources for follow-up and treatment. Treatment costs are only partially covered in most jurisdictions. Only five provinces/territories have formal advisory committees with official mandates. Expensive, restricted access treatment products for adults with inherited metabolic diseases are only fully available in six provinces/territories. There is very limited access to these products in an additional four provinces/territories. To date, specific informed consent for newborn screening is not required in any province or territory.

CONCLUSIONS

Canada is far behind the rest of the developed (and some 'emerging') countries of the world in the field of universal newborn screening. New strategies for advocating expanded screening, follow-up and (long-term) payment of treatment costs on behalf of the potentially affected infants and their families must be devised, and such initiatives should include participation from the new Public Health Agency of Canada.

[Newborn screening for galactosemia: a health economics evaluation]

This study assesses the efficiency of the galactosemia add-on test in neonatal screening performed on regular Guthrie card blood spots. Based on estimated average incidence of galactosemia (1:19,984 newborns) in São Paulo State, Brazil, the study develops a cost-benefit analysis model, using a B/C ratio and a 9.25% annual interest rate in order to decapitalize the results. Sensitivity analysis is also performed, varying (as a function of the interest or discount rate) from 0 and 20% and according to the 95% confidence interval (1:7,494-1:59,953 newborns). The results show that the savings obtained by improved health of galactosemic patients detected early by add-on neonatal screening is superior to the costs (B/C=1.33), characterizing galactosemia add-on testing in neonatal screening as an efficient policy. The lower the prevailing interest rate in the economy, the more efficient the neonatal screening policy.

Inborn errors of metabolism in a neonatology unit: impact and long-term results

BACKGROUND

Inborn errors of metabolism (IEM) have greater repercussions in neonatology units. The goal of our study was to evaluate the impact of IEM in a neonatology unit and the outcome of these neonates.

METHODS

All patients with IEM admitted in our unit were evaluated during an 8-year period for specific diagnosis, clinical features, therapy and long-term neurodevelopment.

RESULTS

The study group was comprised of 31 infants, 18 of which required admission to the neonatal intensive care unit (NICU) (1.63% of income) due to severe symptoms. Twenty-two of the 31 had an earlier diagnosis and treatment due to expanded newborn screening, made from the third day of life. The most frequent diagnosis in the NICU, representing 66.66% (12/18), was diseases that cause an endogenous intoxication. Despite the diagnosis by tandem mass spectrometry, many of these patients had severe clinical symptoms prior to the screening results. Aggressive support was often necessary (extracorporeal removal therapy, mechanical ventilation). Death occurred generally in the first year of life (5/6). The death rate in the NICU was 10.3%. The survivors presented higher scores on the Psychomotor Development Index if the diagnosis of the disease was either made or helped by screening. This also depends on the type of disease.

CONCLUSION

Earlier diagnosis by expanded newborn screening and earlier treatment is essential in order to be able to prevent neurological sequelae.

Galactosaemia in a Brazilian population: high incidence and cost-benefit analysis

OBJECTIVES

To study the incidence of galactosaemia in the state of São Paulo and the benefit/cost (B/C) ratio of the introduction of neonatal screening for galactosaemia, comparing it with a selective approach.

METHODS

An enzymatic-colorimetric assay was used for the screening of total galactose (TG) in a sample of 10% of the births in São Paulo in one year and positive cases were confirmed by the activity of galactose-1-phosphate uridyltransferase (GALT). Detected and referred cases were genotyped using enzyme restriction studies for Q188R, N314D and S135L mutations of the GALT gene. The economic analysis was determined by calculating the B/C ratio and by analysis of sensitivity as a function of the incidence of the disease detected and the variation of the interest rate in the economy.

RESULTS

59 953 newborns were screened for TG, with 3 cases of galactosaemia being identified (0.26% false positives), corresponding to a frequency of 1:19 984 liveborns (95% confidence interval: 1:7494 to 1:59 953). One classical case and one Duarte 2 variant referred to as a selective approach were confirmed. With an incidence of 1:19 984, the B/C ratio was 1.04 for the 11.75% interest rate in effect in Brazil, with values already decapitalized. With a maximum possible incidence of 1:7494, the B/C ratio was 2.79.

DISCUSSION

There is an economic advantage in introducing neonatal screening for galactosaemia in the national neonatal screening programme. This advantage could increase with a reduction of the current interest rates in the economy.

Newborn screening for methylmalonic acidurias--optimization by statistical parameter combination

With the introduction of tandem mass spectrometry, newborn screening for disorders of propionate metabolism became widely available. However, there is controversy whether population screening for these disorders should be performed. The most widely used primary metabolite C(3) itself has a poor specificity or lacks 100% sensitivity for milder forms and/or defects of cobalamin metabolism. Strategies to improve specificity have included the calculation of metabolite ratios (e.g. C(3)/C(2)) or second-tier strategies with analysis of methylmalonic acid or 2-methylcitric acid from the primary screening specimen. We report the results of a new statistical approach to identify parameter combinations that allow for 100% sensitivity as well as increased specificity. The promising results of this alternative approach will have to be substantiated on larger data sets.

Expanded newborn screening in Europe 2007

By January 2007 seven European countries had expanded, and more are considering the expansion of their newborn screening programmes by inclusion of ESI tandem mass spectrometry. We present an overview of the current status of expanded newborn screening programmes in Europe. While the first pilot programmes were initiated in 1998 in Germany, most countries started within the last 3 years. The number of disorders screened for by MS/MS ranges from two disorders (phenylketonuria and medium-chain acyl-CoA dehydrogenase deficiency) in some countries to 20 in others. The number of live births investigated per screening centre varies from 18,000 to 77,000. Few programmes have reported the number of positively identified cases and technical data, although many participate in quality assurance and proficiency test schemes. Given the relatively common genetic background of most European populations and similar health care systems, the reasons for the differences observed appear arbitrary and contrary to the optimal benefit of this important preventive health measure. Harmonization of disease screening panels, spectrum of metabolites analysed, sizes of screening laboratories, analytical procedures, follow-up management and proficiency and quality testing is urgently warranted on the European level. This will hopefully occur before screening by novel applications of tandem mass spectrometry for additional groups of disorders including lysosomal storage disorders and X-linked adrenoleukodystrophy are implemented.

A feasibility study for the newborn screening of spinal muscular atrophy

PURPOSE

The natural history of spinal muscular atrophy suggests that for maximum effect, therapeutics will need to be administered in the earliest phases of the disease. This will require the adoption of techniques for the genetic analysis of affected individuals at the newborn stage. Our objective was to examine the feasibility surrounding the newborn screening for spinal muscular atrophy.

METHODS

We investigated the application of real-time polymerase chain reaction technology for newborn screening. A multiplex assay was designed to identify homozygous deletions in SMN1 exon 7 and validated using 266 samples with defined SMN1 and SMN2 copy numbers. Sensitivity and specificity were then evaluated as part of a newborn screening strategy using DNA from 153 blood spots.

RESULTS

Real-time technology validation demonstrated correct exclusion of all normal and carrier samples, and identified the homozygous SMN1 exon 7 deletions in all 32 affected samples. In the series of blood spots, all 59 affected samples were correctly identified yielding an analytic sensitivity of 100%; 56 normal and 39 carrier samples were correctly excluded yielding an analytic specificity of 100% for this blood spot series.

CONCLUSION

We demonstrate that effective molecular technology exists and that ethics may soon warrant the newborn screening of spinal muscular atrophy.