Urinary Gas Chromatography-mass Spectrometry Research Articles

A rare case of β-ketothiolase deficiency presenting as mimicker of diabetic ketoacidosis

β-ketothiolase (3-oxothiolase, BKT), also called mitochondrial acetoacetyl-coenzyme-A thiolase (T2), is a mitochondrial enzyme involved in isoleucine catabolism and ketone metabolism. BKT or T2 deficiency is inherited as an autosomal recessive trait and results in a rare inborn error of metabolism called alpha-acetoacetic aciduria. Patients with this disorder usually present with intermittent attacks of ketoacidosis. Here, we report a case of BKT deficiency that mimicked diabetic ketoacidosis (DKA) at presentation and discuss the clinical profile and interpretation of laboratory findings. An 8-month-old male child presented with seizures, coma, hyperglycemia, shock, and high anion gap metabolic acidosis with normal serum lactate and negative urinary ketone requiring correction with sodium bicarbonate, management of shock and sepsis, and mechanical ventilation. During his stay in the hospital, he developed ketonuria and episodes of hypoglycemia on a glucose insulin infusion with persistent metabolic acidosis which prompted us to look for an inborn error of metabolism, as hemoglobin A1C (HbA1C) and C-peptide levels were normal. Both tandem mass spectrometry (TMS) and urinary gas chromatography mass spectrometry (GCMS) were confirmatory. Diagnosis of BKT deficiency was further confirmed with genetic testing which revealed a novel homozygous mutation in the acetyl-CoA acetyltransferase 1 (ACAT1) gene. In infants manifesting with clinical features of diabetic ketoacidosis (DKA), cautious interpretation of laboratory findings and consideration of inborn errors of metabolism including the rare BKT deficiency are needed for a favorable outcome and prediction of prognosis.

Clinico-Biochemical Presentation of Classical Organic Aciduria Presenting as Intoxication in Tertiary Care Hospital of Peshawar

Background: About 5 million children died in 2017 in developing countries alone, amongst them 15-20% are due to inherited metabolic disorders. Inherited metabolic disorders like Methyl Malonic Aciduria, Isovaleric aciduria, Glutaric Aciduria type 1, Urea cycle defects, Maple syrup urine disease & multiple carboxylase deficiency present mostly as intoxication, ataxia and convulsions Objective:To find the pattern of classical organic aciduria in children of different age and gender Methodology: This cross-sectional descriptive study was conducted at Paediatrics department of Town Women & Children Hospital, Peshawar from Aug 2018- Aug 2020. Patients aged 0-24 months were included in the study based on inclusion criteria.Clinical data, preliminary investigations and urinary organic acids profile were collected. Data were analysed using SPSS version 21. Results: Out of 178 total patients, 36 patients were diagnosed with classical Organic aciduria in this present study. Mean age of the study population was 0.865+/- 1.07654 years and range of 1 - 2 years. About 20(53%) cases were males, while 16(47%) cases were females. Major clinical and biochemical findings included seizures, feeding difficulties, developmental delay, neurological impairment, and motor weakness, hypoglycemic and metabolic acidosis. Conclusion: The cases positive for inherited metabolic disorder showed a significant prevalence. Methyl Malonic Aciduria was the commonest of the OAs found in Northern areas of Pakistan followed by 3- Methyl Glutaconic aciduria.Simple heel prick test alongside blood gas analysis and confirmatory test by urinary Gas Chromatography Mass Spectrometry were helpful in diagnosis of such inherited metabolic disorder. Keywords: Intoxication; Organic aciduria;Ethyl Malonic aciduria; Fumaric Aciduria

Evaluation of diagnostic accuracy of biomarkers of inborn errors of metabolism in sick neonates: A prospective observational study

ObjectiveTo evaluate the diagnostic accuracy of a set of predefined biomarkers (index test) in diagnosing diseases targeted in expanded newborn screening (ENS) namely organic acidemias, fatty acid oxidation disorders, and amino acid disorders. MethodsThis was a prospective study. The study population consisted of out born neonates admitted to a teaching hospital for the study duration of 12 months. The presence of any of the predefined biomarkers was considered index test positive. Tandem Mass Spectrometry on dried blood samples along with urinary gas chromatography mass spectrometry (GCMS) was considered the gold standard (reference test) for diagnosis of diseases targeted in ENS. ResultsA total of 783 out born neonates were evaluated using the index test and 30 tested positive, out of which, 18 were reference test positive. All index test negative neonates (n = 30) were reference test negative. The index test had a sensitivity of 100%, specificity of 71.42%, with 60% positive predictive value and 100% negative predictive value. The area under ROC curve for the index test was 80%. ConclusionsIn the absence of universal screening programs, the evaluated biomarkers (index test) can be useful to decide which cases should be selectively referred for mass spectrometric techniques. Further multicentric studies are required to assess these biomarkers before incorporating them in national programs.

Age-Specific Cut-off Values of Amino Acids and Acylcarnitines for Diagnosis of Inborn Errors of Metabolism Using Liquid Chromatography Tandem Mass Spectrometry.

Liquid Chromatography tandem mass spectrometry (LC-MS/MS) is used for the diagnosis of more than 30 inborn errors of metabolisms (IEMs). Accurate and reliable diagnosis of IEMs by quantifying amino acids (AAs) and acylcarnitines (ACs) using LC-MS/MS systems depend on the establishment of age-specific cut-offs of the analytes. This study aimed to (1) determine the age-specific cut-off values of AAs and ACs in Bangladesh and (2) validate the LC-MS/MS method for diagnosis of the patients with IEMs. A total of 570 enrolled healthy participants were divided into 3 age groups, namely, (1) newborns (1-7 days), (2) 8 days–7 years, and (3) 8–17 years, to establish the age-specific cut-offs for AAs and ACs. Also, 273 suspected patients with IEMs were enrolled to evaluate the reliability of the established cut-off values. Quantitation of AAs and ACs was performed on an automated LC-MS/MS system using dried blood spot (DBS) cards. Then the specimens of the enrolled clinically suspected patients were analyzed by the established method. Nine patients came out as screening positive for different IEMs, including two borderline positive cases of medium-chain acyl-CoA dehydrogenase deficiency (MCAD). A second-tier test for confirmation of the screening positive cases was conducted by urinary metabolic profiling using gas chromatography- mass spectrometry (GC-MS). Out of 9 cases that came out as screening positive by LC-MS/MS, seven cases were confirmed by urinary GC-MS analysis including 3 cases with phenylketonuria, 1 with citrullinemia type II, 1 with methylmalonic acidemia, 1 with isovaleric acidemia and 1 with carnitine uptake defect. Two borderline positive cases with MCAD were found negative by urinary GC-MS analysis. In conclusion, along with establishment of a validated LC-MS/MS method for quantitation of AAs and ACs from the DBS cards, the study also demonstrates the presence of predominantly available IEMs in Bangladesh.

Urinary gas chromatography mass spectrometry metabolomics in asphyxiated newborns undergoing hypothermia: from the birth to the first month of life.

Perinatal asphyxia is a severe clinical condition affecting around four million newborns worldwide. It consists of an impaired gas exchange leading to three biochemical components: hypoxemia, hypercapnia and metabolic acidosis. The aim of this longitudinal experimental study was to identify the urine metabolome of newborns with perinatal asphyxia and to follow changes in urine metabolic profile over time. Twelve babies with perinatal asphyxia were included in this study; three babies died on the eighth day of life. Total-body cooling for 72 hours was carried out in all the newborns. Urine samples were collected in each baby at birth, after 48 hours during hypothermia, after the end of the therapeutic treatment (72 hours), after 1 week of life, and finally after 1 month of life. Urine metabolome at birth was considered the reference against which to compare metabolic profiles in subsequent samples. Quantitative metabolic profiling in urine samples was measured by gas chromatography mass spectrometry (GC-MS). The statistical approach was conducted by using the multivariate analysis by means of principal component analysis (PCA) and orthogonal partial least square discriminant analysis (OPLS-DA). Pathway analysis was also performed. The most important metabolites depicting each time collection point were identified and compared each other. At birth before starting therapeutic hypothermia (TH), urine metabolic profiles of the three babies died after 7 days of life were closely comparable each other and significantly different from those in survivors. In conclusion, a plethora of data have been extracted by comparing the urine metabolome at birth with those observed at each time point collection. The modifications over time in metabolites composition and concentration, mainly originated from the depletion of cellular energy and homeostasis, seems to constitute a fingerprint of perinatal asphyxia.

Exploring the Role of Different Neonatal Nutrition Regimens during the First Week of Life by Urinary GC-MS Metabolomics.

In this study, a gas-chromatography mass spectrometry (GC-MS) metabolomics study was applied to examine urine metabolite profiles of different classes of neonates under different nutrition regimens. The study population included 35 neonates, exclusively either breastfed or formula milk fed, in a seven-day timeframe. Urine samples were collected from intrauterine growth restriction (IUGR), large for gestational age (LGA), and appropriate gestational age (AGA) neonates. At birth, IUGR and LGA neonates showed similarities in their urine metabolite profiles that differed from AGA. When neonates started milk feeding, their metabolite excretion profile was strongly characterized by the different diet regimens. After three days of formula milk nutrition, urine had higher levels of glucose, galactose, glycine and myo-inositol, while up-regulated aconitic acid, aminomalonic acid and adipic acid were found in breast milk fed neonates. At seven days, neonates fed with formula milk shared higher levels of pseudouridine with IUGR and LGA at birth. Breastfed neonates shared up-regulated pyroglutamic acid, citric acid, and homoserine, with AGA at birth. The role of most important metabolites is herein discussed.

Use of metabolomics to elucidate the metabolic perturbation associated with hypertension in a black South African male cohort: the SABPA study

There is concern about the increasing burden of essential hypertension in urban–dwelling black South Africans, especially males. Several studies have investigated urbanization and hypertension in South Africans, but in–depth metabolomics studies on these urbanized hypertensives are still lacking. We aimed to investigate hypertension via two metabolomics methods in order to explore underlying biological mechanisms, demonstrating the effectiveness of these methods in cardiovascular research. A comprehensive characterization of a group (n = 25) of black male South Africans was performed using urinary gas chromatography–mass spectrometry and liquid chromatography–mass spectrometry metabolic profiling in conjunction with 24–hour ambulatory blood pressure readings and anthropometric, clinical, and biochemical markers. Average 24–hour blood pressure readings served as the grouping variable, and test subjects were divided into quintiles. Statistical analyses were performed on Quintile 1 (normotensive subjects) and Quintile 5 (extreme hypertensive subjects). After feature selection was performed, several metabolites and cardiometabolic risk markers, including abdominal obesity and markers of liver damage, inflammation, and oxidative stress were significantly perturbed in Quintile 5 (hypertensives) compared with Quintile 1 (P < .05). Pathway analysis revealed perturbations in several systems involved in ethanol metabolism via shifted global NADH/NAD+ ratio. Although alcohol abuse has been established as a risk factor for hypertension, this study illustrated a metabolic perturbation associated with alcohol abuse, contributing to the development of hypertension—possibly by altering bioenergetics through a shift in the NADH/NAD+ ratio. Following this finding, future intervention studies on alcohol moderation, as well as further enhancement of metabolomics methods in cardiovascular research are highly recommended.