Normal plasma free amino acid levels in Thai children.

Analysis of plasma free amino acid levels is important for diagnosis of inborn errors of metabolism. Traditionally, this is performed using commercially available dedicated amino acid analyzers, but few such instruments are available in Thailand, and many are not used in routine operations. Here, the authors describe the analysis of plasma free amino acid levels in 57 normal children by reverse-phase HPLC and pre-column derivatization with phenylisothiocyanate. Plasma free amino levels are reported as mean +/- SD and 95 per cent confidence interval of mean for each of 5 age groups: 0-6 months; 6-12 months; 1-3 years; 3-6 years; 6-12 years. Mean amino acid levels were generally similar in all age groups (p > or = 0.01), except that hydroxyproline tended to be higher in the 0-6 months age group compared to other age groups (p<0.01). Comparisons were made between the present data with the normal free plasma amino acid levels in children of similar age groups reported both in Thailand and overseas in terms of both mean +/- SD and maximum and minimum values. Overall, our methodology involving HPLC can identify 35 amino acid derivatives, including all the major amino acids except for cysteine, which is substantially more than the number reported in earlier work on plasma free amino acid levels in normal Thai children. Moreover, the present methodology gives mean +/- SD values similar to an overseas report. For these reasons, HPLC should be considered as an alternative approach in laboratories, where demand does not justify the need for dedicated amino acid analyzers. However, there can be substantial variations between the results from different laboratories, and each laboratory should establish its own normal values.

Plasma amino acid and urine organic acid analyses of methylmalonic acidemia in a Thai infant.

Methylmalonic acidemia is an inborn error of organic acid metabolism resulting from defects in methylmalonyl CoA mutase. Analysis of plasma free amino acids in a 15-month-old Thai infant by HPLC showed marked elevation of glycine. HPLC analysis of urinary organic acids showed high levels of methylmalonic acid.

Detection of inherited metabolic disorders via tandem mass spectrometry in Thai infants.

From a retrospective study in Medical Genetics Unit, Department of Pediatrics, Siriraj Hospital Faculty of Medicine, Mahidol University in Bangkok (1983-1988), the estimated pediatric patients with clinically suspected IEM are approximately 2-4% of total annual pediatrics admission of 5,000 or more. This is, a low estimation since survey from all teaching hospitals in the country including the largest Children's Hospital in Bangkok indicated the presence of numerous IEM. However, most IEM were clinically diagnosed with limited laboratory facilities. We started a collaboration with Magee Womens Hospital of Pittsburgh and NeoGen Screening, USA; using tandem mass spectrometry to diagnose high risk infants and children for IEM from July 1993 to March 1998. Of total 146 samples sent, we detected numerous metabolic disorders (11.2%) eg phenylketonuria, organic acidemia, maple syrup urine disease, isovaleric acidemia, methylmalonic acidemia, albinism, translocase/carnitine palmitoyltransferase type II, G6PD deficiency and lysinuric protein intolerance.

Detection of inborn errors of metabolism in Thai infants via gas chromatography and mass spectrometry.

We had studied inherited metabolic disorders at the Department of Pediatrics, Siriraj Hospital Faculty of Medicine, Mahidol University since 1987 using limited resources available and collaboration with other laboratories, both in Thailand and The United States. Since April 1998, we started a collaboration with MILS and Kanazawa Medical University, the Japan, studying inborn errors of metabolism in Asian Countries using urine filter paper and a new GC/MS method. We have since successfully discovered several patients with metabolic disorders. Out of 33 (high-risk) cases we sent for biochemical diagnosis (during April-July 1998), 13 abnormal results were found which is approximately 39.4%. Inherited metabolic disorders identified were as follows: medium-chain acyl CoA dehydrogenase deficiency (MCAD), multiple carboxylase deficiency (MCD), methylmalonic acidemia (MMA), Fanconi syndrome, galactosemia and neuroblastoma.

Neonatal screening for congenital hypothyroidism and phenylketonuria at Siriraj Hospital, Mahidol University, Bangkok, Thailand--a pilot study.

A newborn screening program for congenital hypothyroidism (CH) and phenylketonuria (PKU), a pilot study, was initiated at the Medical Genetics Unit, Department of Pediatrics, Siriraj Hospital Faculty of Medicine, Mahidol University in Bangkok, Thailand from January 1994 to December 1998, using dried blood spots (DBS). A total of 18,739 infants (out of 85,150 livebirths) were screened (22 % coverage). Three cases of congenital hypothyroidism (CH) were identified (incidence of 1: 6,246, livebirths), by enzyme linked immunosorbent (ELISA) and fluoroimmunoassays using a cut-off level of TSH >20 microlU/ml: the recall rate of 0.24%. The screening for PKU was done by fluorometric (Guthrie) and enzyme linked immunosorbent (ELISA) methods; using cut-off levels of phenylalanine > 4 mg/dl and > 3.6 mg/dl respectively, with a recall rate of 0.13%. There was no PKU found. Our study, a voluntary program, emphasizes the importance of parental education and consent; specimen collection and handling; appropriate follow-up and referral to specialists for treatment and counseling. Routine newborn screening for CH and PKU is being established to ascertain the maximum coverage, using recommendations and guidelines from this pilot study.

Inherited metabolic disorders in Thailand--Siriraj experience.

The incidence of inborn errors of metabolism (IEM) in Thailand is yet unknown. However, by estimation it is generally accepted to be 1 in 5,000. From a survey in 7 medical schools from different parts of the country and a large pediatric hospital in Bangkok, we found numerous cases of IEM nationwidc. Thesc were amino acid disorders, carbohydrate disorders, urea cycle defects, peroxisomal, lysosomal storage disorders, and many others. Since Thais are quite homogeneous in their genetic make-up; it is, therefore, very likely that IEM is much more prevalent than we realized. With the exception of thalassemias, IFAM is probably very common in Thailand and other countries in the Asia-Pacific region. IEM identified were amino acid disorders eg phenylketonuria, maple syrup urine disease: urea cycle disorders eg ornithine transcarbamylase deficincy (OTC), argininosuccinic lyase deficiency (ALD), argininosuccinic acid synthetasc deficiency (ASD); glycogen storage disorders eg Pompe's discase, Von Gierkc's; organic acid disorders eg, isovaleric acidemia, methylmalonic acidemia. Lysosmal storagc disorders identified were GM1 gangliosidosis, mucolipidosis II, Hurler, Hunter, Maroteaux-Lamy, Sialidosis (neuraminidase deficicncy), Sly, Scheie, Gaucher, Niemann-Pick, Sandhoff and many other neurodegeneraative disorders identified were rhizomelic chondrodysplasia punctata (RCDP) and Zellweger. Recently fatty acid oxidation disorders: MCAD, translocase deficiency and multiple carbosxylase deficiency 9biotinidase deficiency) were also identified.

Plasma amino acid analyses in two cases of maple syrup urine disease.

Maple syrup urine disease is a rare inborn error of metabolism, characterized by elevated plasma levels of branched chain amino acids and urinary excretion of branched chain keto acids. Plasma amino acid levels in two subjects were followed by deproteinizing plasma, derivatizing the free amino acids with phenylisothiocyanate, and analysis by HPLC. The results indicate that valine, leucine and isoleucine are elevated in Maple syrup urine disease, and that leucine remains high even after dietary treatment.

Lipoprotein(a) in nephrotic syndrome.

Serum lipoprotein(a) levels were measured in 27 patients with idiopathic nephrotic syndrome (NS), 14 patients with systemic lupus erythematosus (SLE) and 30 healthy controls. Lp(a) levels were significantly elevated in both idiopathic NS (53.4 + 36.2) and SLE (49.3+ 41.9) compared with controls (9.5+ 5.7) (p < 0.001). Fifty nine percent of idiopathic NS and 50 percent of SLE had Lp(a) more than 30 mg/dl. In 19 patients with idiopathic NS, serum Lp(a) levels fell markedly in 12 patients who responded to prednisolone therapy while, 7 patients with partial and no response had serum Lp(a), cholesterol, triglycerides and albumin levels not different from pretreatment period vs 6 months therapy. Lp(a) levels correlated significantly with proteinuria, serum cholesterol and triglycerides (r = 0.8, 0.6, 0.6) in idiopathic nephrotic syndrome and correlated inversely with serum albumin (r = -0.9). The SLE patients had the same pattern of correlation among these parameters and Lp(a) levels except for triglycerides. The high levels of Lp(a) in the NS could be one of the risk factors for atherosclerosis and thrombotic events associated with this disorder. In conclusion, the present study confirmed that patients with idiopathic NS and SLE had markedly increased serum level of Lp(a), in conjunction with other lipid abnormalities. The serum Lp(a) levels decreased substantially in all NS patients who experienced remission. In addition, the study also demonstrated a relationship between serum Lp(a) levels and serum albumin, cholesterol and triglycerides. An elevated Lp(a) level may be useful in guiding the physician towards more aggressive care to detect coronary artery disease early in patients at risk.

Erythrocytic glutathione peroxidase and lipid peroxidation in chronic renal failure patients.

Glutathione peroxidase (GPx) plays an important role in scavenging reactive oxygen metabolites and preventing the oxidative stress in the body. The purpose of this study is to investigate the levels of erythrocytic GPx activity and plasma malondialdehyde (MDA) in 25 chronic renal failure patients compared with 25 normal controls. The GPx activity in chronic renal failure patients was significantly lower than controls (22.6 + 5.5 U/gHb as 30.5 + 9.5 U/gHb respectively, p = 0.0033) and plasma malondialdehyde was significantly high in chronic renal failure patients compared to controls (78.89 + 55.38 ตmol/l vs 7.71 + 3.26 ตmol/l respec-tively, p< 0.0001). Lipid peroxidation product (MDA) correlated significantly with hemoglobin, hematorit, serum creatinine and creatinine clearance. Glutathione peroxidase also correlated significantly with serum creztinine. It was concluded that a decrease in reactive oxygen metabolite scavngers and increase in lipid peroxidation might contribute to might contribute to increase hemolysis and anemia in chronic renal failure.