Dietary practices in propionic acidemia: A European survey

Background

The definitive dietary management of propionic acidaemia (PA) is unknown although natural protein restriction with adequate energy provision is of key importance.

Aim

To describe European dietary practices in the management of patients with PA prior to the publication of the European PA guidelines.

Methods

This was a cross-sectional survey consisting of 27 questions about the dietary practices in PA patients circulated to European IMD dietitians and health professionals in 2014.

Results

Information on protein restricted diets of 186 PA patients from 47 centres, representing 14 European countries was collected. Total protein intake [PA precursor-free L-amino acid supplements (PFAA) and natural protein] met WHO/FAO/UNU (2007) safe protein requirements for age in 36 centres (77%). PFAA were used to supplement natural protein intake in 81% (n = 38) of centres, providing a median of 44% (14–83%) of total protein requirement. Seventy-four per cent of patients were prescribed natural protein intakes below WHO/FAO/UNU (2007) safe levels in one or more of the following age groups: 0–6 m, 7–12 m, 1–10 y, 11–16 y and > 16 y. Sixty-three per cent (n = 117) of patients were tube fed (74% gastrostomy), but only 22% received nocturnal feeds.

Conclusions

There was high use of PFAA with intakes of natural protein commonly below WHO/FAO/UNU (2007) safe levels. Optimal dietary management can only be determined by longitudinal, multi-centre, prospective case controlled studies. The metabolic instability of PA and small patient cohorts in each centre ensure that this is a challenging undertaking.

Cardiac complications of congenital disorders of glycosylation (CDG): a systematic review of the literature

Congenital disorders of glycosylation (CDG) are inborn errors of metabolism due to protein and lipid hypoglycosylation. This rapidly growing family of genetic diseases comprises 103 CDG types, with a broad phenotypic diversity ranging from mild to severe poly-organ -system dysfunction. This literature review summarizes cardiac involvement, reported in 20% of CDG. CDG with cardiac involvement were divided according to the associated type of glycosylation: N-glycosylation, O-glycosylation, dolichol synthesis, glycosylphosphatidylinositol (GPI)-anchor biosynthesis, COG complex, V-ATPase complex, and other glycosylation pathways. The aim of this review was to document and interpret the incidence of heart disease in CDG patients. Heart disorders were grouped into cardiomyopathies, structural defects, and arrhythmogenic disorders. This work may contribute to improved early management of cardiac complications in CDG.

Evaluation of the revised New Zealand national newborn screening protocol for congenital hypothyroidism

OBJECTIVE

The aim of this study was to assess the performance of the revised New Zealand (NZ) newborn screening TSH cut-offs for congenital hypothyroidism (CHT).

METHODS

Screening data over 24 months were obtained from the NZ newborn metabolic screening programme, which utilizes a 2-tier system of direct clinical referral for infants with markedly elevated TSH, and second samples from those with mild TSH elevation. We evaluated the impact of a reduced TSH threshold (50 to 30 mIU/l blood) for direct notification and a lower cut-off (15 to 8 mIU/l blood) applied to second samples and babies older than 14 days.

RESULTS

In 2013 and 2014, 117 528 infants underwent newborn screening for CHT. Fifty-two CHT cases were identified by screening (47 general newborn population, five repeat testing in low-birth-weight infants) and one case was missed. Thirty-two infants with screening TSH ≥30 mIU/l were directly referred at a median of 9 days (5-14) and 15 with TSH 15-29 mIU/l were referred after a second sample at a median of 20 days (9-52, P < 0·001). All directly referred infants were confirmed as CHT cases with no earlier referrals as a result of the reduced threshold. The lower TSH cut-off applied to second samples lead to the identification of six extra cases of CHT (15% increase) from seven extra clinical referrals.

CONCLUSIONS

The NZ screening programme achieved a 15% increase in CHT case detection for minimal increase in workload or anxiety for families of healthy infants. A further decrease in the threshold for direct referral may allow earlier diagnoses.

Dietary practices in isovaleric acidemia: A European survey

Background

In Europe, dietary management of isovaleric acidemia (IVA) may vary widely. There is limited collective information about dietetic management.

Aim

To describe European practice regarding the dietary management of IVA, prior to the availability of the E-IMD IVA guidelines (E-IMD 2014).

Methods

A cross-sectional questionnaire was sent to all European dietitians who were either members of the Society for the Study of Inborn Errors of Metabolism Dietitians Group (SSIEM-DG) or whom had responded to previous questionnaires on dietetic practice (n = 53). The questionnaire comprised 27 questions about the dietary management of IVA.

Results

Information on 140 patients with IVA from 39 centres was reported. 133 patients (38 centres) were given a protein restricted diet. Leucine-free amino acid supplements (LFAA) were routinely used to supplement protein intake in 58% of centres. The median total protein intake prescribed achieved the WHO/FAO/UNU [2007] safe levels of protein intake in all age groups. Centres that prescribed LFAA had lower natural protein intakes in most age groups except 1 to 10 y. In contrast, when centres were not using LFAA, the median natural protein intake met WHO/FAO/UNU [2007] safe levels of protein intake in all age groups. Enteral tube feeding was rarely prescribed.

Conclusions

This survey demonstrates wide differences in dietary practice in the management of IVA across European centres. It provides unique dietary data collectively representing European practices in IVA which can be used as a foundation to compare dietary management changes as a consequence of the first E-IMD IVA guidelines availability.

Use of plasma human herpesvirus-8 viral load measurement: evaluation of practice in three UK HIV treatment centres

A retrospective audit of plasma human herpesvirus-8 (HHV-8) viral load testing was performed in three HIV treatment centres over 24 months. Reasons for testing (360 tests) were: symptoms of systemic inflammatory response syndrome (SIRS) (fever, lymphadenopathy and raised inflammatory markers); monitoring in known HHV-8 pathology other than Kaposi sarcoma (KS); investigation of known/suspected KS, and other/no reason. Of patients with multicentric Castleman disease (MCD), 14/16 (88%) had detectable plasma HHV-8, as did 27/45 (60%) with biopsy proven or clinically confirmed KS, and 6/19 (32%) with lymphoma. Neither of the two patients with MCD and no detectable HHV-8 had SIRS symptoms at the time of the test. There was wide variation between centres in the indications prompting HHV-8 testing, with a more conservative approach resulting in a higher proportion of positive results. Measuring plasma HHV-8 in the absence of SIRS symptoms, established HHV-8 disease monitoring, or confirmed/suspected KS is unlikely to yield detectable HHV-8 thus allowing potential cost savings.

The Risk of Fatty Acid Oxidation Disorders and Organic Acidemias in Children with Normal Newborn Screening

New Zealand has undertaken expanded newborn screening since 2006. During that period there have been no reported cases of fatty acid oxidation disorders or organic acidemias that have been diagnosed clinically that the screening programme missed. However there may have been patients that presented clinically that were not diagnosed correctly or notified.In order to investigate the false-negative screening rate a case-control study was undertaken whereby the clinical coding data and relevant medical records were reviewed for 150 controls and 525 cases. The cases had normal newborn screening but with key analytes and/or ratios just below the notification level for individual disorders and thus in theory were most at risk of having metabolic disease.Two cases had medical histories suggestive of metabolic disease and thus could represent a false-negative screen. One of these had marginally elevated octanoyl carnitine levels and thus possible medium-chain acyl Co-A dehydrogenase deficiency (MCADD) while the other had elevated isovaleryl carnitine and thus may have been a case of isovaleric acidemia (IVA). However, subsequent molecular analysis revealed that the diagnosis of MCADD and IVA was unlikely.Despite relatively high cut-offs the New Zealand Newborn Metabolic Screening Programme does not appear to have missed any confirmed cases of fatty acid oxidation disorders and organic acidemias in its first 8 years of expanded newborn screening. This would suggest a similar low false-negative screening rate in centres with comparable screening protocols and would indicate that the risk of fatty acid oxidation disorders and classical organic acidemias in children who had normal newborn screening is low.

The natural history of elevated tetradecenoyl-L-carnitine detected by newborn screening in New Zealand: implications for very long chain acyl-CoA dehydrogenase deficiency screening and treatment

Very long chain acyl-CoA dehydrogenase deficiency (VLCADD, OMIM #201475) has been increasingly diagnosed since the advent of expanded newborn screening (NBS). Elevated levels of tetradecenoyl-L-carnitine (C14:1) in newborn screening blood spot samples are particularly common in New Zealand, however this has not translated into increased VLCADD clinical presentations. A high proportion of screen-positive cases in NZ are of Maori or Pacific ethnicity and positive for the c.1226C > T (p.Thr409Met) ACADVL gene variant. We performed a retrospective, blinded, case-control study of 255 cases, born between 2006 and 2013, with elevated NBS C14:1 levels between 0.9 and 2.4 μmol/L, below the NZ C14:1 notification cut-off of 2.5 μmol/L. Coded healthcare records were audited for cases and age- and ethnicity- matched controls. The clinical records of those with possible VLCADD-related symptoms were reviewed. The follow-up period was 6 months to 7 years. Two of 247 cases (0.8 %) had possible VLCADD-like symptoms while four of 247 controls (2 %) had VLCADD-like symptoms (p = 0.81). Maori were overrepresented (68 % of the cohort vs 15 % of population). Targeted analysis of the c.1226 locus revealed the local increase in screening C14:1 levels is associated with the c.1226C > T variant (97/152 alleles tested), found predominantly in Maori and Pacific people. There was no increase in clinically significant childhood disease, irrespective of ethnicity. The study suggests that children with elevated C14:1, between 0.9-2.4 μmol/L, on NBS are at very low risk of clinically significant childhood disease. A minimally interventional approach to managing these patients is indicated, at least in the New Zealand population.

Antenatal screening for aneuploidy--surveying the current situation and planning for non-invasive prenatal diagnosis in New Zealand

AIMS

To gauge clinical opinion about the current system and possible changes as well as providing a forum for education about Non-Invasive Prenatal Testing (NIPT).

METHODS

A series of workshops for doctors and midwives, supported by the National Screening Unit of the Ministry of Health and the Royal Australian and New Zealand College of Obstetricians and Gynaecologists, were held in the main centres of New Zealand. Following a brief education session, a structured evaluation of current screening and future possibilities was undertaken by questionnaire.

RESULTS

One hundred and eight maternity carers participated in 5 workshops. Over 40% identified barriers to current screening. More than 60% would support NIPT in the first trimester. The majority of carers provided their own counselling support for women.

CONCLUSIONS

The survey has shown general enthusiasm for the introduction of publically funded NIPT into prenatal screening in New Zealand. Barriers to utilisation of the current system have been identified and enhancements to screening performance with guidelines around conditions to be screened for would be supported.

240 PRECISE GENOME EDITING OF PDX1 BY DIRECT INJECTION OF TRANSCRIPTION ACTIVATOR-LIKE EFFECTOR NUCLEASES (TALENS) INTO PARTHENOGENETIC PIG EMBRYOS

Pancreatic and duodenal homeobox 1 (PDX1) is one of the transcription factors involved in pancreatic organogenesis and plays a critical role as an early lineage marker of pancreatic specification and β-cell differentiation. In mature pancreas, PDX1 regulates a large number of genes involved in maintaining β-cell identity and function. In mice and humans, its homozygous disruption results in pancreas agenesis, while heterozygous mutations have been associated with early-onset (MODY) and late-onset forms of Type II diabetes mellitus in humans. Knockout of the PDX1 gene in pigs may lead to the generation of an apancreatic phenotype, which in turn could allow the potential generation of an exogenic pancreas. Moreover, this could help to create a large animal model for human diabetes. We used transcription activator-like effector nucleases (TALEN) technology with the aim of studying the efficiency of precise editing by homologous recombination in parthenogenetically activated porcine embryos. Mature oocytes were activated by incubation in ionomycin (10 µM) for 20 min, followed by a 4-h incubation in DMAP (2 mM) + cytochalasin B (7.5 µg mL–1). Cytoplasmic injection was performed 14 h post-activation. Post injections, embryos were cultured for 6 days in NCSU23+BSA media at 38.5°C in a 5% CO2 atmosphere. We first evaluated the activity of a pair of TALENs targeting the functional domain of the PDX1 gene. Three concentrations of mRNA were microinjected (10, 20, and 40 ng µL–1) and blastocysts were analysed for non-homologous end-joining (NHEJ) by sequencing. The efficiency of indel mutations at the PDX1-target loci (either monoallelic or biallelic) was 34.5, 52.6, and 80.0% for the 10, 20, and 40 ng µL–1 concentrations, respectively. Next, we tested whether ssODNs (single-stranded oligodeoxynucleotide) coinjected with TALENs would permit precise homology direct repair (HDR) in porcine parthenotes. TALEN mRNA (40 ng µL–1) was coinjected with an ssODN donor template (50 ng µL–1) designed to incorporate a novel stop codon, HindIII restriction site, and a frame shift mutation. Cleavage and blastocyst rates were recorded at Days 2 and 6 of development, respectively, in the TALEN/ssODN injected group (n = 260 zygotes), buffer-injected embryos (n = 135 zygotes), and the non-injected group (n = 132 zygotes). Day 7 embryos were analysed for NHEJ and HDR by RFLP assay and Sanger sequencing after whole-genome amplification and PCR. Blastocyst rates were 15% (TALEN/ssODN-injected group), 27% (buffer-injected group), and 34% (non-injected group). A total of 30 blastocysts were analysed for HDR after whole-genome amplification. The majority of analysed blastocysts (28/30, 93%) were mutant. Among them, 10 (36%) incorporated the ssODN, from which 3 (30%) showed a KO genotype with a precise biallelic modification. We report here a highly efficient and precise TALEN-mediated gene knockout in swine embryos, which represents an alternative to cloning for phenotype evaluation of knockouts related to organogenesis.

Practices in prescribing protein substitutes for PKU in Europe: No uniformity of approach

BACKGROUND

There appears little consensus concerning protein requirements in phenylketonuria (PKU).

METHODS

A questionnaire completed by 63 European and Turkish IMD centres from 18 countries collected data on prescribed total protein intake (natural/intact protein and phenylalanine-free protein substitute [PS]) by age, administration frequency and method, monitoring, and type of protein substitute. Data were analysed by European region using descriptive statistics.

RESULTS

The amount of total protein (from PS and natural/intact protein) varied according to the European region. Higher median amounts of total protein were prescribed in infants and children in Northern Europe (n=24 centres) (infants <1 year, >2-3g/kg/day; 1-3 years of age, >2-3 g/kg/day; 4-10 years of age, >1.5-2.5 g/kg/day) and Southern Europe (n=10 centres) (infants <1 year, 2.5 g/kg/day, 1-3 years of age, 2 g/kg/day; 4-10 years of age, 1.5-2 g/kg/day), than by Eastern Europe (n=4 centres) (infants <1 year, 2.5 g/kg/day, 1-3 years of age, >2-2.5 g/kg/day; 4-10 years of age, >1.5-2 g/kg/day) and with Western Europe (n=25 centres) giving the least (infants <1 year, >2-2.5 g/kg/day, 1-3 years of age, 1.5-2 g/kg/day; 4-10 years of age, 1-1.5 g/kg/day). Total protein prescription was similar in patients aged >10 years (1-1.5 g/kg/day) and maternal patients (1-1.5 g/kg/day).

CONCLUSIONS

The amounts of total protein prescribed varied between European countries and appeared to be influenced by geographical region. In PKU, all gave higher than the recommended 2007 WHO/FAO/UNU safe levels of protein intake for the general population.

Newborn screening for congenital adrenal hyperplasia in New Zealand, 1994-2013

OBJECTIVE

The objective of the study was to evaluate the efficacy of national newborn screening for severe congenital adrenal hyperplasia (CAH) in New Zealand over the past 20 years.

METHODS

Newborn screening for CAH is performed through the estimation of 17-hydroxyprogesterone by a Delfia immunoassay. CAH cases diagnosed in the newborn period from 1994 to 2013 were identified from Newborn Metabolic Screening Programme records.

RESULTS

Between 1994 and 2013, 44 neonates (28 females, 16 males) were diagnosed with CAH, giving an incidence of 1:26 727. Almost half (n = 21) of the newborns with CAH were detected solely via screening (not clinically suspected), including 21% of all affected females. Among the group solely ascertained by screening, 17-hydroxyprogesterone sampling occurred at a mean age of 3.3 days (range 2-8 d), the duration from sampling to notification was 5.2 days (0-12 d), and treatment was initiated at 12.0 days (6-122 d). Vomiting was present in 14% of those ascertained by screening, but none had hypotension or collapse at diagnosis. Increasing age at treatment was correlated with a progressive decrease in serum sodium (r = -0.56; P < .0001) and an increase in serum potassium concentrations (r = 0.38; P = .017). Compared with newborns diagnosed by screening alone, those clinically diagnosed were predominantly female (96% vs 29%; P < .0001), notification occurred earlier (4.8 vs 8.5 d; P = .002), and had higher serum sodium (136.8 vs 130.8 mmol/L; P < .0001) and lower serum potassium (5.3 vs 6.0 mmol/L; P = .011) concentrations.

CONCLUSIONS

Screening alone accounted for nearly 50% cases of CAH detected in the newborn period, including a fifth of affected females, indicating that clinical diagnosis is unreliable in both genders. Symptoms were mild at diagnosis and there were no adrenal crises. This study confirms the benefits of newborn CAH screening.

Interim estimates of 2013/14 influenza clinical severity and vaccine effectiveness in the prevention of laboratory-confirmed influenza-related hospitalisation, Canada, February 2014

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Dietary management of urea cycle disorders: European practice

BACKGROUND

There is no published data comparing dietary management of urea cycle disorders (UCD) in different countries.

METHODS

Cross-sectional data from 41 European Inherited Metabolic Disorder (IMD) centres (17 UK, 6 France, 5 Germany, 4 Belgium, 4 Portugal, 2 Netherlands, 1 Denmark, 1 Italy, 1 Sweden) was collected by questionnaire describing management of patients with UCD on prescribed protein restricted diets.

RESULTS

Data for 464 patients: N-acetylglutamate synthase (NAGS) deficiency, n=10; carbamoyl phosphate synthetase (CPS1) deficiency, n=29; ornithine transcarbamoylase (OTC) deficiency, n=214; citrullinaemia, n=108; argininosuccinic aciduria (ASA), n=80; arginase deficiency, n=23 was reported. The majority of patients (70%; n=327) were aged 0-16y and 30% (n=137) >16y. Prescribed median protein intake/kg body weight decreased with age with little variation between disorders. The UK tended to give more total protein than other European countries particularly in infancy. Supplements of essential amino acids (EAA) were prescribed for 38% [n=174] of the patients overall, but were given more commonly in arginase deficiency (74%), CPS (48%) and citrullinaemia (46%). Patients in Germany (64%), Portugal (67%) and Sweden (100%) were the most frequent users of EAA. Only 18% [n=84] of patients were prescribed tube feeds, most commonly for CPS (41%); and 21% [n=97] were prescribed oral energy supplements.

CONCLUSIONS

Dietary treatment for UCD varies significantly between different conditions, and between and within European IMD centres. Further studies examining the outcome of treatment compared with the type of dietary therapy and nutritional support received are required.

Dietary practices in pyridoxine non-responsive homocystinuria: a European survey

BACKGROUND

Within Europe, the management of pyridoxine (B6) non-responsive homocystinuria (HCU) may vary but there is limited knowledge about treatment practice.

AIM

A comparison of dietetic management practices of patients with B6 non-responsive HCU in European centres.

METHODS

A cross-sectional audit by questionnaire was completed by 29 inherited metabolic disorder (IMD) centres: (14 UK, 5 Germany, 3 Netherlands, 2 Switzerland, 2 Portugal, 1 France, 1 Norway, 1 Belgium).

RESULTS

181 patients (73% >16 years of age) with HCU were identified. The majority (66%; n=119) were on dietary treatment (1-10 years, 90%; 11-16 years, 82%; and >16 years, 58%) with or without betaine and 34% (n=62) were on betaine alone. The median natural protein intake (g/day) on diet only was, by age: 1-10 years, 12 g; 11-16 years, 11 g; and >16 years, 45 g. With diet and betaine, median natural protein intake (g/day) by age was: 1-10 years, 13 g; 11-16 years, 20 g; and >16 years, 38 g. Fifty-two percent (n=15) of centres allocated natural protein by calculating methionine rather than a protein exchange system. A methionine-free l-amino acid supplement was prescribed for 86% of diet treated patients. Fifty-two percent of centres recommended cystine supplements for low plasma concentrations. Target treatment concentrations for homocystine/homocysteine (free/total) and frequency of biochemical monitoring varied.

CONCLUSION

In B6 non-responsive HCU the prescription of dietary restriction by IMD centres declined with age, potentially associated with poor adherence in older patients. Inconsistencies in biochemical monitoring and treatment indicate the need for international consensus guidelines.