Enhanced interpretation of newborn screening results without analyte cutoff values.

PURPOSE: To improve quality of newborn screening by tandem mass spectrometry with a novel approach made possible by the collaboration of 154 laboratories in 49 countries. METHODS: A database of 767,464 results from 12,721 cases affected with 60 conditions was used to build multivariate pattern recognition software that generates tools integrating multiple clinically significant results into a single score. This score is determined by the overlap between normal and disease ranges, penetration within the disease range, differences between conditions, and weighted correction factors. RESULTS: Ninety tools target either a single condition or the differential diagnosis between multiple conditions. Scores are expressed as the percentile rank among all cases with the same condition and are compared to interpretation guidelines. Retrospective evaluation of past cases suggests that these tools could have avoided at least half of 279 false-positive outcomes caused by carrier status for fatty-acid oxidation disorders and could have prevented 88% of known false-negative events. CONCLUSION: Application of this computational approach to raw data is independent from single analyte cutoff values. In Minnesota, the tools have been a major contributing factor to the sustained achievement of a false-positive rate below 0.1% and a positive predictive value above 60%.

Microstructural Characterization of Laser Weld of Hot-Stamped Al-Si Coated 22MnB5 and Modification of Weld Properties by Hybrid Welding.

The presence of Al-Si coating on 22MnB5 leads to the formation of large ferritic bands in the dominantly martensitic microstructure of butt laser welds. Rapid cooling of laser weld metal is responsible for insufficient diffusion of coating elements into the steel and incomplete homogenization of weld fusion zone. The Al-rich regions promote the formation of ferritic solid solution. Soft ferritic bands cause weld joint weakening. Laser welds reached only 64% of base metal's ultimate tensile strength, and they always fractured in the fusion zone during the tensile tests. We implemented hybrid laser-TIG welding technology to reduce weld cooling rate by the addition of heat of the arc. The effect of arc current on weld microstructure and mechanical properties was investigated. Thanks to the slower cooling, the large ferritic bands were eliminated. The hybrid welds reached greater ultimate tensile strength compared to laser welds. The location of the fracture moved from the fusion zone to a tempered heat-affected zone characterized by a drop in microhardness. The minimum of microhardness was independent of heat input in this region.

Analysis of aminoimidazole ribosides by capillary electrophoresis--diagnosing defects in second part of purine biosynthetic pathway.

BACKGROUND: Only three inherited metabolic defects have been identified in purine de novo synthesis (PDNS). We present here CE methods for diagnosing defects in the second half of PDNS (from sixth to tenth enzymatic conversion) based on analysis of aminoimidazole ribosides - dephosphorylated intermediates - in urine. METHODS: Assays were performed in an uncoated fused-silica capillary using two electrophoretic separation systems: 60 mmol/l borate - 2-amino-2-methyl-1-propanol-80 mmol/l sodium dodecylsulfate (pH 9.6) and 200 mmol/l phosphate - sodium (pH 1.8). RESULTS: The reported conditions allowed separation of all metabolites from major urinary constituents with analysis time less than 10 min and separation efficiency of 220 and 350 thousands theoretical plates per meter for borate and phosphate system, respectively. The intra- and interday imprecisions were less than 4.4% and 9.9% CV. Potential usefulness of the methods was demonstrated on samples from a patient with adenylosuccinate lyase deficiency and Chinese hamster ovary cell lines defective in PDNS. CONCLUSIONS: CE is a useful and effective tool in the analysis of aminoimidazole ribosides which enables diagnosis of known as well as not so far identified inherited defects of PDNS pathway.

Diagnosing AICA-ribosiduria by capillary electrophoresis.

AICA-ribosiduria is a recently discovered inherited metabolic disease caused by a defect in final steps of purine de novo biosynthesis-5-amino-4-imidazolecarboxamide ribotide (AICAR)-transformylase/inosinemonophosphate (IMP)-cyclohydrolase (ATIC). A rapid and selective capillary electrophoretic method for screening of patients with AICA-ribosiduria is described. The method is based on direct ultraviolet detection of 5-amino-4-imidazolecarboxamide (AICA) and 5-amino-4-imidazolecarboxamide riboside (AICAr) in untreated urine. Background electrolyte consists of 100mM malonic acid adjusted with gamma-aminobutyric acid (pH 2.7). Under the given separation conditions both compounds of interest are well separated from other substances with separation efficiency of 1020000 and 130000 theoretical plates/m for AICA and AICAr, respectively. Total analysis time is 3 min with the limits of detection of 3.6 microM and 4.5 microM for AICA and AICAr, respectively. The usefulness of the presented method for screening of patients with ATIC deficiency is demonstrated on samples of Chinese hamster ovary cell line defective in ATIC activity, spiked urine samples and urine samples from patients treated with high-dose MTX which do not excrete increased amounts of AICA and AICAr compared to untreated controls (p<0.05). The described method is fast and effective enough for diagnostic applications.

Targeted metabolomic analysis of plasma samples for the diagnosis of inherited metabolic disorders.

Metabolomics has become an important tool in clinical research and diagnosis of human diseases. In this work we focused on the diagnosis of inherited metabolic disorders (IMDs) in plasma samples using a targeted metabolomic approach. The plasma samples were analyzed with the flow injection analysis method. All the experiments were performed on a QTRAP 5500 tandem mass spectrometer (AB SCIEX, U.S.A.) with electrospray ionization. The compounds were measured in a multiple reaction monitoring mode. We analyzed 50 control samples and 34 samples with defects in amino acid metabolism (phenylketonuria, maple syrup urine disease, tyrosinemia I, argininemia, homocystinuria, carbamoyl phosphate synthetase deficiency, ornithine transcarbamylase deficiency, nonketotic hyperglycinemia), organic acidurias (methylmalonic aciduria, propionic aciduria, glutaric aciduria I, 3-hydroxy-3-methylglutaric aciduria, isovaleric aciduria), and mitochondrial defects (medium-chain acyl-coenzyme A dehydrogenase deficiency, carnitine palmitoyltransferase II deficiency). The controls were distinguished from the patient samples by principal component analysis and hierarchical clustering. Approximately 80% of patients were clearly detected by absolute metabolite concentrations, the sum of variance for first two principle components was in the range of 44-55%. Other patient samples were assigned due to the characteristic ratio of metabolites (the sum of variance for first two principle components 77 and 83%). This study has revealed that targeted metabolomic tools with automated and unsupervised processing can be applied for the diagnosis of various IMDs.