Post-natal gestational age assessment using targeted metabolites of neonatal heel prick and umbilical cord blood: A GARBH-Ini cohort study from North India.

Background: Accurate assessment of gestational age (GA) and identification of preterm birth (PTB) at delivery is essential to guide appropriate post-natal clinical care. Undoubtedly, dating ultrasound sonography (USG) is the gold standard to ascertain GA, but is not accessible to the majority of pregnant women in low- and middle-income countries (LMICs), particularly in rural areas and small secondary care hospitals. Conventional methods of post-natal GA assessment are not reliable at delivery and are further compounded by a lack of trained personnel to conduct them. We aimed to develop a population-specific GA model using integrated clinical and biochemical variables measured at delivery. Methods: We acquired metabolic profiles on paired neonatal heel prick (nHP) and umbilical cord blood (uCB) dried blood spot (DBS) samples (n = 1278). The master data set consists of 31 predictors from nHP and 24 from uCB after feature selection. These selected predictors including biochemical analytes, birth weight, and placental weight were considered for the development of population-specific GA estimation and birth outcome classification models using eXtreme Gradient Boosting (XGBoost) algorithm. Results: The nHP and uCB full model revealed root mean square error (RMSE) of 1.14 (95% confidence interval (CI) = 0.82-1.18) and of 1.26 (95% CI = 0.88-1.32) to estimate the GA as compared to actual GA, respectively. In addition, these models correctly estimated 87.9 to 92.5% of the infants within ±2 weeks of the actual GA. The classification models also performed as the best fit to discriminate the PTB from term birth (TB) infants with an area under curve (AUC) of 0.89 (95% CI = 0.84-0.94) for nHP and an AUC of 0.89 (95% CI = 0.85-0.95) for uCB. Conclusion: The biochemical analytes along with clinical variables in the nHP and uCB data sets provide higher accuracy in predicting GA. These models also performed as the best fit to identify PTB infants at delivery.

Inborn Errors of Ketogenesis: Novel Variants, Clinical Presentation, and Follow-Up in a Series of Four Patients.

Inborn errors of ketogenesis are rare disorders that result in acute and fulminant decompensation during lipolytic stress, particularly in infants and children. These include mitochondrial 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase (HMGCS) deficiency and HMG-CoA lyase (HMGCL) deficiency. In this series, we describe the clinical, biochemical, and molecular profiles of four patients along with dietary interventions and their outcomes on a long-term follow-up. Two patients each of HMGCS and HMGCL deficiency were evaluated with clinical history, biochemical investigations, including tandem mass spectrometry (TMS) and urine gas chromatography-mass spectrometry (GCMS). Molecular analysis was performed by whole-exome sequencing, as well as exon array validated by long-range polymerase chain reaction. All individuals were diagnosed with acute metabolic decompensation in the early infancy period except one with HMGCL deficiency who had the first presentation at 5 years of age. Central nervous system manifestations, severe metabolic acidosis, hyperammonemia, hypoglycemia with a normal lactate, and absence of urinary ketones were observed in all the affected individuals. The disorder was life-threatening in three individuals and one succumbed to the illness. TMS was nonspecific and urine GCMS revealed dicarboxylic aciduria in HMGCS deficiency. Both the patients with HMGCL deficiency demonstrated elevated 3 hydroxyisovaleryl carnitine levels in TMS and metabolites of leucine degradation in urine GCMS. We identified five novel variants that included a large deletion involving exon 2 in HMGCL gene. There was no evidence of long-term neurological sequelae in the living individuals. Diet with moderation of fat intake was followed in two individuals with HMGCS deficiency. Low leucine and protein diet with moderation of fat intake was followed in the individual with HMGCL deficiency. All affected individuals are thriving well with no further major metabolic decompensation.

Detection of IEMs by Mass Spectrometry Techniques in High-Risk Children: A Pilot Study.

OBJECTIVES: To determine the incidence and types of inborn errors of metabolism (IEMs) in high-risk children using mass spectrometry techniques. METHODS: Children considered high-risk for IEM were screened for metabolic diseases during a 3-y period. Dried blood spots and urine samples were analyzed by tandem mass spectrometry (LC-MS/MS) and gas chromatograph-mass spectrometry (GCMS). Samples with abnormal amino acids were confirmed by high-performance liquid chromatography (HPLC). RESULTS: Eight hundred and twenty-two suspected cases were evaluated; of which, 87 possible cases of IEMs were identified. Homocystinuria (n = 51) was the most common IEM detected followed by biotinidase deficiency (n = 7), glutaric aciduria type 1 (n = 7), and carnitine uptake defect (n = 6). Overall, there were 45 (51.7%) cases of organic acidemia, 31 cases (35.6%) of amino acid defect, 9 (10.3%) cases of fatty-acid oxidation disorders, and 2 (2.3%) cases of probable mitochondrial disorder. CONCLUSION: IEMs are common in India, with a hospital-based incidence of 1 in approximately 6642 among high-risk children. Screening of high-risk children by mass spectrometry techniques is a valuable strategy for early diagnosis of IEMs where universal newborn screening is not yet available.

Development of Flow Injection Analysis Method for the Second-Tier Estimation of Succinylacetone in Dried Blood Spot of Newborn Screening.

Tyrosinemia type 1 (TYR1) is a devastating aminoacidopathy, leading to mortality without medical intervention. Although, detection and quantification of tyrosine in dried blood spot (DBS) is possible, but being a non-specific marker for TYR1 and its frequent association with transient neonatal tyrosinemia limits its applicability. Despite, Succinylacetone (SUAC) being a pathognomonic marker for TYR1, but not often detectable by routine newborn screening (NBS). We envisaged to determine SUAC in DBS by an in-house flow injection analysis method on a liquid chromatography/tandem mass spectrometry (LC-MS/MS). Succinylacetone was eluted from the residual 3.2 mm DBS of primary NBS by an extraction solution containing acetonitrile-water-formic acid mixture containing stable-isotope labelled internal standard (IS) for SUAC and hydrazine. Detection and quantification was performed by the mass spectrometer using multiple reaction monitoring mode at m/z 155.1 → 109.1 for SUAC and m/z 160.1 → 114.1 for the SUAC IS. The assay was linear over a calibration range of 0.122-117.434 µmol/L. The Intra-day and Inter-day precision and accuracy for the assay was determined at two different levels of SUAC (2.542 µmol/L and 14.641 µmol/L), which showed a coefficient of variation of (6.91% and 12.65%) and (8.57% and 12.27%) respectively. The accuracy also ranged between 101.2 and 103.87%.This method provided the necessary sensitivity, precision, accuracy, recovery and linearity and hence, has the potential to reduce the false positive, false negative results which significantly minimise the cost involved in the screening and follow up of TYR1 patients. SUPPLEMENTARY INFORMATION: The online version of this article (10.1007/s12291-020-00944-z) contains supplementary material, which is available to authorized users.

Mutation Analyses in Selected Exons of the MUT Gene in Indian Patients with Methylmalonic Acidemia.

Deficiency or diminished activity of a cobalamin dependent enzyme methylmalonyl-CoA mutase causes inborn error of metabolism called methylmalonic acidemia (MMA). In this study we elucidated the spectrum of mutations in 21 Indian mut MMA patients by direct sequencing. Sequence analysis identified a total of 70 mutations in exon 2, 9, 11 and 12 of MUT gene. Out of which 26 mutations were predicted to be deleterious and rest were benign. The 23 novel mutations consist of four nonsense mutations (p.N6*, p.G539*, p.E609* and p.I671*), twelve missense mutations (p.K128I, p.N547T, p.D554Y, p.A558T, p.R559P, p.A631T, p.I647T, p.E656D, p.V657E, p.Q660H, p.K679N, and p.G696Y) and seven frame shift mutations (c.375_376insA, c.1642delA, c.1655delC, c.1825_1826insT, c.1957delGA, c.2014delA and c.2062_2063insGA). All of them are point mutations or micro rearrangements. Three of these mutations (p.K621N, p.G648D, p.G630E) have been previously reported; all of them are missense mutations. The mutations are distributed throughout the exon 2, 9, 11 and 12, 38.4 % mutation are located in exon 12.

Liquid-Liquid Extraction and Solid Phase Extraction for Urinary Organic Acids: A Comparative Study from a Resource Constraint Setting.

Pre analytical process of extraction for accurate detection of organic acids is a crucial step in diagnosis of organic acidemias by GCMS analysis. This process is accomplished either by solid phase extraction (SPE) or by liquid-liquid extraction (LLE). Both extraction procedures are used in different metabolic laboratories all over the world. In this study we compared these two extraction procedures in respect of precision, accuracy, percent recovery of metabolites, number of metabolites isolated, time and cost in a resource constraint setup. We observed that the mean recovery from SPE was 84.1 % and by LLE it was 77.4 % (p value <0.05). Moreover, the average number of metabolites isolated by SPE and LLE was 161.8 ± 18.6 and 140.1 ± 20.4 respectively. The processing cost of LLE was economical. In a cost constraint setting using LLE may be the practical option if used for organic acid analysis.