Mild Acquired von Willebrand Syndrome and Cholestasis in Pediatric and Adult Patients with Fontan Circulation.

Background: Hemodynamic alterations in Fontan patients (FP) are associated with hemostatic dysbalance and Fontan-associated liver disease. Studies of other hepatopathologies indicate an interplay between cholestasis, tissue factor (TF), and von Willebrand factor (VWF). Hence, we hypothesized a relationship between the accumulation of bile acids (BA) and these hemostatic factors in FP. Methods: We included 34 FP (Phenprocoumon n = 15, acetylsalicylic acid (ASA) n = 16). BA were assessed by mass spectrometry. TF activity and VWF antigen (VWF:Ag) were determined by chromogenic assays. VWF collagen-binding activity (VWF:CB) was assessed via ELISA. Results: Cholestasis was observed in 6/34 FP (total BA ≥ 10 µM). BA levels and TF activity did not correlate (p = 0.724). Cholestatic FP had lower platelet counts (p = 0.013) from which 5/6 FP were not treated with ASA. VWF:Ag levels were increased in 9/34 FP and significantly lower in FP receiving ASA (p = 0.044). Acquired von Willebrand syndrome (AVWS) was observed in 10/34-FP, with a higher incidence in cholestatic FP (4/6) (p = 0.048). Conclusions: Cholestasis is unexpectedly infrequent in FP and seems to be less frequent under ASA therapy. Therefore, ASA may reduce the risk of advanced liver fibrosis. FP should be screened for AVWS to avoid bleeding events, especially in cholestatic states.

A Systematic Review of the Transthoracic Impedance during Cardiac Defibrillation.

For cardiac defibrillator testing and design purposes, the range and limits of the human TTI is of high interest. Potential influencing factors regarding the electronic configurations, the electrode/tissue interface and patient characteristics were identified and analyzed. A literature survey based on 71 selected articles was used to review and assess human TTI and the influencing factors found. The human TTI extended from 12 to 212 Ω in the literature selected. Excluding outliers and pediatric measurements, the mean TTI recordings ranged from 51 to 112 Ω with an average TTI of 76.7 Ω under normal distribution. The wide range of human impedance can be attributed to 12 different influencing factors, including shock waveforms and protocols, coupling devices, electrode size and pressure, electrode position, patient age, gender, body dimensions, respiration and lung volume, blood hemoglobin saturation and different pathologies. The coupling device, electrode size and electrode pressure have the greatest influence on TTI.

Novel subtype of mucopolysaccharidosis caused by arylsulfatase K (ARSK) deficiency.

BACKGROUND: Mucopolysaccharidoses (MPS) are monogenic metabolic disorders that significantly affect the skeleton. Eleven enzyme defects in the lysosomal degradation of glycosaminoglycans (GAGs) have been assigned to the known MPS subtypes (I-IX). Arylsulfatase K (ARSK) is a recently characterised lysosomal hydrolase involved in GAG degradation that removes the 2-O-sulfate group from 2-sulfoglucuronate. Knockout of Arsk in mice was consistent with mild storage pathology, but no human phenotype has yet been described. METHODS: In this study, we report four affected individuals of two unrelated consanguineous families with homozygous variants c.250C>T, p.(Arg84Cys) and c.560T>A, p.(Leu187Ter) in ARSK, respectively. Functional consequences of the two ARSK variants were assessed by mutation-specific ARSK constructs derived by site-directed mutagenesis, which were ectopically expressed in HT1080 cells. Urinary GAG excretion was analysed by dimethylene blue and electrophoresis, as well as liquid chromatography/mass spectrometry (LC-MS)/MS analysis. RESULTS: The phenotypes of the affected individuals include MPS features, such as short stature, coarse facial features and dysostosis multiplex. Reverse phenotyping in two of the four individuals revealed additional cardiac and ophthalmological abnormalities. Mild elevation of dermatan sulfate was detected in the two subjects investigated by LC-MS/MS. Human HT1080 cells expressing the ARSK-Leu187Ter construct exhibited absent protein levels by western blot, and cells with the ARSK-Arg84Cys construct showed markedly reduced enzyme activity in an ARSK-specific enzymatic assay against 2-O-sulfoglucuronate-containing disaccharides as analysed by C18-reversed-phase chromatography followed by MS. CONCLUSION: Our work provides a detailed clinical and molecular characterisation of a novel subtype of mucopolysaccharidosis, which we suggest to designate subtype X.

Amino Acid and Phospholipid Metabolism as an Indicator of Inflammation and Subtle Cardiomyopathy in Patients with Marfan Syndrome.

Patients with Marfan syndrome (MFS) have an increased risk of aortic aneurysm formation, dissection and development of a subtle cardiomyopathy. We analyzed amino acid and lipid metabolic pathways in MFS patients, seeking biomarker patterns as potential monitoring tools of cardiovascular risk with deterioration of myocardial function. We assessed myocardial function in 24 adult MFS patients and compared traditional laboratory values and mass spectrometry-based amino acid, phospholipid and acylcarnitine metabolomes in patients with those in healthy controls. Analytes for which values differed between patients and controls were subjected to regression analysis. A high proportion of patients had signs of impaired diastolic function and elevated serum levels of NT-proBNP. Patients had lower serum levels of taurine, histidine and PCaeC42:3 than controls. The evidence of diastolic dysfunction, aortic root dimensions and history of aortic root surgery correlated with NT-proBNP and taurine levels. Alterations in serum levels of metabolism derived analytes link MFS pathophysiology with inflammation, oxidative stress and incipient cardiomyopathy.

Deep learning in spatiotemporal cardiac imaging: A review of methodologies and clinical usability.

The use of different cardiac imaging modalities such as MRI, CT or ultrasound enables the visualization and interpretation of altered morphological structures and function of the heart. In recent years, there has been an increasing interest in AI and deep learning that take into account spatial and temporal information in medical image analysis. In particular, deep learning tools using temporal information in image processing have not yet found their way into daily clinical practice, despite its presumed high diagnostic and prognostic value. This review aims to synthesize the most relevant deep learning methods and discuss their clinical usability in dynamic cardiac imaging using for example the complete spatiotemporal image information of the heart cycle. Selected articles were categorized according to the following indicators: clinical applications, quality of datasets, preprocessing and annotation, learning methods and training strategy, and test performance. Clinical usability was evaluated based on these criteria by classifying the selected papers into (i) clinical level, (ii) robust candidate and (iii) proof of concept applications. Interestingly, not a single one of the reviewed papers was classified as a "clinical level" study. Almost 39% of the articles achieved a "robust candidate" and as many as 61% a "proof of concept" status. In summary, deep learning in spatiotemporal cardiac imaging is still strongly research-oriented and its implementation in clinical application still requires considerable efforts. Challenges that need to be addressed are the quality of datasets together with clinical verification and validation of the performance achieved by the used method.

Safety and efficacy of the endothelin receptor antagonist macitentan in pediatric pulmonary hypertension.

BACKGROUND: Macitentan, a dual endothelin receptor antagonist (ERA), was approved in 2014 for the treatment of adults with idiopathic pulmonary arterial hypertension (PAH). Once-per-day dosing and low potential hepatic toxicity make macitentan an appealing therapeutic option for children with PAH, but reports on its use in pediatric patients are still lacking. METHODS: Prospective observational study of 18 children [10 male; median age: 8.5, minimum (min.): 0.6, maximum (max.): 16.8 years] with pulmonary hypertension (PH). Four of these 18 patients were treatment-naïve and started on a de novo macitentan therapy. The remaining 14/18 children were already on a PH-targeted pharmacotherapy (sildenafil or bosentan as monotherapy or in combination). Nine children who were on bosentan were switched to macitentan. We analyzed the 6-minute walking distance (6MWD), NYHA functional class (FC)/modified ROSS score, invasive hemodynamics, echocardiographic variables and the biomarker N-terminal pro-brain natriuretic peptide (NT-proBNP). RESULTS: The median follow up was 6 months (min.: 0.5, max.: 30). Macitentan treatment was associated with improvement of invasive hemodynamics, e.g., the ratio of mean pulmonary arterial pressure/mean systemic arterial pressure decreased from a median of 62% (min.: 30%, max.: 87%) to 49% (min.: 30%, max.: 69%), P<0.05; pulmonary vascular resistance index (PVRi) decreased from a median of 7.6 (min.: 3.3, max.: 11.5) to 4.8 Wood units × m2 body surface area (min.: 2.5, max.: 10), P<0.05. The tricuspid annular plane systolic excursion (TAPSE) increased from a median of 1.4 (min.: 0.8, max.: 2.8) to 1.9 (min.: 0.8, max.: 2.7) cm, (P<0.05). NT-proBNP values decreased from a median of 272 (min.: 27, max.: 2,010) to 229 (min.: 23, max.: 814) pg/mL under macitentan therapy (P<0.05). The 6MWD and NYHA FC/modified ROSS score did not change significantly. CONCLUSIONS: This is the first prospective study of macitentan pharmacotherapy in infants and children with PH <12 years of age. Except in one patient, macitentan treatment was well tolerated and was associated with improvements in invasive hemodynamics, longitudinal systolic RV function (TAPSE) and serum NT-proBNP values.

A novel network-based approach for discovering dynamic metabolic biomarkers in cardiovascular disease.

Metabolic biomarkers may play an important role in the diagnosis, prognostication and assessment of response to pharmacological therapy in complex diseases. The process of discovering new metabolic biomarkers is a non-trivial task which involves a number of bioanalytical processing steps coupled with a computational approach for the search, prioritization and verification of new biomarker candidates. Kinetic analysis provides an additional dimension of complexity in time-series data, allowing for a more precise interpretation of biomarker dynamics in terms of molecular interaction and pathway modulation. A novel network-based computational strategy for the discovery of putative dynamic biomarker candidates is presented, enabling the identification and verification of unexpected metabolic signatures in complex diseases such as myocardial infarction. The novelty of the proposed method lies in combining metabolic time-series data into a superimposed graph representation, highlighting the strength of the underlying kinetic interaction of preselected analytes. Using this approach, we were able to confirm known metabolic signatures and also identify new candidates such as carnosine and glycocholic acid, and pathways that have been previously associated with cardiovascular or related diseases. This computational strategy may serve as a complementary tool for the discovery of dynamic metabolic or proteomic biomarkers in the field of clinical medicine.

Former Very Preterm Infants Show an Unfavorable Cardiovascular Risk Profile at a Preschool Age.

Cardiovascular disease is the leading cause of death worldwide. Evidence points towards an unfavorable cardiovascular risk profile of former preterm infants in adolescence and adulthood. The aim of this study was to determine whether cardiovascular risk predictors are detectable in former very preterm infants at a preschool age. Five- to seven-year-old children born at <32 weeks' gestational age were included in the study. Same-aged children born at term served as controls. Basic data of study participants were collected by means of follow-up databases and standardized questionnaires. At study visit, anthropometric data, blood pressure readings and aortic intima-media thickness were assessed. Blood samples were obtained after an overnight fast. In comparison to children born at term, former preterm infants had higher systolic and diastolic blood pressure readings (odds ratio [95% confidence interval] per 1-SD higher blood pressure level 3.2 [2.0-5.0], p<0.001 and 1.6 [1.1-1.2], p = 0.008), fasting glucose levels (OR [95% CI] 5.2 [2.7-10.1], p<0.001), homeostasis model assessment index (OR [95% CI] 1.6 [1.0-2.6], p = 0.036), and cholesterol levels (OR [95% CI] 2.1 [1.3-3.4], p = 0.002). Systolic prehypertension (23.7% vs. 2.2%; OR [95% CI] 13.8 [3.1-60.9], p = 0.001), elevated glucose levels (28.6% vs. 5.9%; OR [95% CI] 6.4 [1.4-28.8], p = 0.016), and hypercholesterolemia (77.4% vs. 52.9%; OR [95% CI] 3.0 [1.3-7.1], p = 0.010) were significantly more prevalent in the preterm group. As former very preterm infants display an unfavorable cardiovascular risk profile already at a preschool age, implementation of routine cardiovascular follow-up programs might be warranted.

Aortic Elastic Properties in Preschool Children Born Preterm.

OBJECTIVE: Preterm birth predisposes children to the development of cardiovascular diseases in adulthood. The aim of this study was to characterize elastic properties of the aorta at preschool age and test the hypothesis that prematurity is associated with decreased aortic distensibility and increased stiffness, both of which are predictors of increased cardiovascular risk. APPROACH AND RESULTS: In an observational study of 76 five- to seven-year-old children born at a gestational age <32 weeks and 79 term-born controls, elastic parameters of the ascending and descending abdominal aorta were determined noninvasively by means of M mode echocardiographic tracings and calculated using computerized wall contour analysis. Compared with children born at term, the preterm group showed significantly reduced distensibility and increased stiffness of the descending abdominal aorta. These results remained significant under multivariable adjustment for birth weight z score, maternal smoking in pregnancy, maternal education, family history of cardiovascular disease, breastfeeding, childhood nutrition, and current body mass index z score (multivariable odds ratios and 95% confidence intervals 5.1, 1.7-15.9; P=0.005 and 2.8, 1.0-7.9; P=0.046, respectively). Further adjustment for intravenous lipid therapy attenuated the strength of association. Elastic properties of the ascending aorta did not differ between the 2 study groups. CONCLUSIONS: Children born preterm are characterized by decreased elastic properties of the descending abdominal aorta potentially attributable to impaired viscoelastic properties of and lipid damage to the aorta. Clinical follow-up of preterm infants with a focus on aortic elastic properties may be useful for tailoring early prevention programs and counteracting cardiovascular risk in adulthood.

Bioinformatic-driven search for metabolic biomarkers in disease.

The search and validation of novel disease biomarkers requires the complementary power of professional study planning and execution, modern profiling technologies and related bioinformatics tools for data analysis and interpretation. Biomarkers have considerable impact on the care of patients and are urgently needed for advancing diagnostics, prognostics and treatment of disease. This survey article highlights emerging bioinformatics methods for biomarker discovery in clinical metabolomics, focusing on the problem of data preprocessing and consolidation, the data-driven search, verification, prioritization and biological interpretation of putative metabolic candidate biomarkers in disease. In particular, data mining tools suitable for the application to omic data gathered from most frequently-used type of experimental designs, such as case-control or longitudinal biomarker cohort studies, are reviewed and case examples of selected discovery steps are delineated in more detail. This review demonstrates that clinical bioinformatics has evolved into an essential element of biomarker discovery, translating new innovations and successes in profiling technologies and bioinformatics to clinical application.

Quantitative sequence analysis of FBN1 premature termination codons provides evidence for incomplete NMD in leukocytes.

We improved, evaluated, and used Sanger sequencing for quantification of single nucleotide polymorphism (SNP) variants in transcripts and gDNA samples. This improved assay resulted in highly reproducible relative allele frequencies (e.g., for a heterozygous gDNA 50.0+/-1.4%, and for a missense mutation-bearing transcript 46.9+/-3.7%) with a lower detection limit of 3-9%. It provided excellent accuracy and linear correlation between expected and observed relative allele frequencies. This sequencing assay, which can also be used for the quantification of copy number variations (CNVs), methylations, mosaicisms, and DNA pools, enabled us to analyze transcripts of the FBN1 gene in fibroblasts and blood samples of patients with suspected Marfan syndrome not only qualitatively but also quantitatively. We report a total of 18 novel and 19 known FBN1 sequence variants leading to a premature termination codon (PTC), 26 of which we analyzed by quantitative sequencing both at gDNA and cDNA levels. The relative amounts of PTC-containing FBN1 transcripts in fresh and PAXgene-stabilized blood samples were significantly higher (33.0+/-3.9% to 80.0+/-7.2%) than those detected in affected fibroblasts with inhibition of nonsense-mediated mRNA decay (NMD) (11.0+/-2.1% to 25.0+/-1.8%), whereas in fibroblasts without NMD inhibition no mutant alleles could be detected. These results provide evidence for incomplete NMD in leukocytes and have particular importance for RNA-based analyses not only in FBN1 but also in other genes.

Impaired elastic properties of the ascending aorta persist within the first 3 years after neonatal coarctation repair.

Abnormal elastic properties of the ascending aorta in patients with coarctation of the aorta (CoA) are already present in neonates before and after successful repair. To prove the midterm outcome for vascular pathology, a cohort of 15 patients was prospectively reevaluated. In this study, 15 patients after neonatal CoA repair (study group) and 15 healthy normal children (control group) were examined (mean age, 3.0 +/- 1.0 years). The aortic wall stiffness index and distensibility were calculated using ascending and abdominal aortic M-mode diameters and noninvasive estimation of pulse pressure. The study group was compared with the control group and with its own previously obtained pre- and postoperative measurements. After a mean follow-up period of 2.9 +/- 0.9 years, the elastic properties of the ascending aorta remained impaired in the study group compared with the control group (distensibility: 62 +/- 28 vs 94 +/- 34; p = 0.01; stiffness index: 4.4 +/- 1.9 vs 2.7 +/- 1.0; p = 0.008). At follow-up evaluation, the elasticity of the ascending aorta in the study group showed no change from the initial neonatal findings (distensibility: 63 +/- 24 vs 62 +/- 28; p = 0.82; stiffness index: 4.0 +/- 1.6 vs 4.4 +/- 1.9; p = 0.65). In both groups, descending aortic elasticity increased during the follow-up period. Our data suggest that the diminished elastic properties of the prestenotic arteries remain unchanged years after successful CoA repair. Comparisons with the neonatal data showed no evidence for remodeling of the ascending aorta in this group.

Prolonged QTc intervals and decreased left ventricular contractility in patients with propionic acidemia.

OBJECTIVE: To investigate electrophysiological and functional signs of myocardial damage in patients with propionic acidemia (PA), an inborn error of metabolism caused by deficiency of propionyl CoA carboxylase (PCC). STUDY DESIGN: In an observational longitudinal study 10 patients with PA (6 boys and 4 girls) ranging between 2.5 and 20.2 (median 9.0) years of age at last follow-up were investigated over a period of up to 20 (mean 7.4) years using 12-lead electrocardiograms (ECGs), 24-hour continuous ECG recordings, bicycle exercise testings, and echocardiography with special focus on repolarization abnormalities such as corrected QT interval (QTc) prolongation, ventricular dysrhythmias, and left ventricular systolic function. RESULTS: QTc interval was prolonged (>440 ms) in 70% of patients beyond infanthood. Continuous ECG recordings revealed rhythm disturbances in 20% of patients. M-mode echocardiographic left ventricular function was reduced (fractional shortening [FS] <30%) in 40%. One patient showed signs of dilated cardiomyopathy. CONCLUSIONS: The majority of patients with PA (even in clinically stable situations) have disturbances in cardiac electrophysiology that can contribute to cardiac complications. Possible mechanisms include effects of toxic metabolites or deprivation of essential substrates. To avoid life-threatening complications, we recommend regular cardiological evaluations in this group of patients.

Different patterns of aortic wall elasticity in patients with Marfan syndrome: a noninvasive follow-up study.

OBJECTIVE: Aortic complications determine the life expectancy of most patients with Marfan syndrome. To find out whether there is heterogenous aortic involvement among patients and, if there is, to characterize aortic patterns and response to long-term beta-blocker therapy, we investigated aortic elastic properties before and during beta-blocker treatment. METHODS: In 46 patients with Marfan syndrome (age, 17.4 +/- 11.1 years) and 46 healthy control subjects, ascending and descending aortic elastic parameters were determined noninvasively before and after 39 +/- 16 months of beta-blocker treatment with atenolol. RESULTS: Aortic diameters and distensibility distinguished Marfan patients and controls with a sensitivity of 85% and a specificity of 87%. Cluster analysis revealed 4 patterns of aortic phenotypic expression: (1) reduced ascending aortic elasticity (46% of patients), (2) diminished ascending and descending aortic elasticity (17%), (3) minimal alterations of ascending and descending aortic elasticity (20%), and (4) reduced descending aortic elasticity (17%). During follow-up, aortic elastic properties improved in 21 (70%) of 30 patients and deteriorated in 9 (30%) irrespective of beta-blocker dosage. Improvement was observed in 100% of patients (n = 7; age, 5.3 +/- 4.2 years) with end-diastolic aortic root diameters between 20 and 30 mm and in 61% of patients (14/23; age, 20.5 +/- 10.0 years) with root diameters between 30 and 52 mm. CONCLUSIONS: Aortic elastic parameters distinguish between patients with Marfan syndrome and healthy controls and show the pattern of regional aortic involvement. Improvement or deterioration during follow-up can influence therapeutic decisions to prevent aortic dissection and rupture. Young age, small root diameter, and high distensibility are favorable prognostic factors.

Identification and in silico analyses of novel TGFBR1 and TGFBR2 mutations in Marfan syndrome-related disorders.

Very recently, heterozygous mutations in the genes encoding transforming growth factor beta receptors I (TGFBR1) and II (TGFBR2) have been reported in Loeys-Dietz aortic aneurysm syndrome (LDS). In addition, dominant TGFBR2 mutations have been identified in Marfan syndrome type 2 (MFS2) and familial thoracic aortic aneurysms and dissections (TAAD). In the past, mutations of these genes were associated with atherosclerosis and several human cancers. Here, we report a total of nine novel and one known heterozygous sequence variants in the TGFBR1 and TGFBR2 genes in nine of 70 unrelated individuals with MFS-like phenotypes who previously tested negative for mutations in the gene encoding the extracellular matrix protein fibrillin-1 (FBN1). To assess the pathogenic impact of these sequence variants, in silico analyses were performed by the PolyPhen, SIFT, and Fold-X algorithms and by means of a 3D homology model of the TGFBR2 kinase domain. Our results showed that in all but one of the patients the pathogenic effect of at least one sequence variant is highly probable (c.722C > T, c.799A > C, and c.1460G > A in TGFBR1 and c.773T > G, c.1106G > T, c.1159G > A, c.1181G > A, and c.1561T > C in TGFBR2). These deleterious alleles occurred de novo or segregated with the disease in the families, indicating a causative association between the sequence variants and clinical phenotypes. Since TGFBR2 mutations found in patients with MFS-related disorders cannot be distinguished from heterozygous TGFBR2 mutations reported in tumor samples, we emphasize the importance of segregation analysis in affected families. In order to be able to find the mutation that is indeed responsible for a MFS-related phenotype, we also propose that genetic testing for sequence alterations in TGFBR1 and TGFBR2 should be complemented by mutation screening of the FBN1 gene.

Dural ectasia in children with Marfan syndrome: a prospective, multicenter, patient-control study.

UNLABELLED: The clinical diagnosis of Marfan syndrome in childhood is difficult, because symptoms may not have developed to their full expression until adulthood. The Ghent nosology for the diagnosis of Marfan syndrome classifies dural ectasia as a major diagnostic criterion. More than two thirds of adult patients with Marfan syndrome show dural ectasia, while the frequency in childhood is unknown. This prospective multicenter observational patient-control study was performed to identify pathologic changes of the lumbosacral spine in young patients with Marfan syndrome. DESIGN: Prospective clinical trial, multicentric, cross-sectional. SETTING: MRI of the lumbosacral spine. PATIENTS: Twenty patients with proven Marfan syndrome, 20 patients suspicious for Marfan syndrome and 38 healthy controls. OUTCOME MEASURES: Vertebral body diameter (VBD) from L1 to S1, dural sac diameter (DSD) from L1 to S1, dural sac ratio (DSR), qualitative assessment of the lumbosacral spine. RESULTS: DSD and VBD in different age groups were higher in patients with proven or suspected Marfan syndrome than in healthy controls (DSD: L1, 6-8 years, P < 0.05). VBD related to body height showed a similar growth related increase in patients with proven or suspected Marfan syndrome and controls. DSD related to body height was elevated in patients with proven or suspected Marfan syndrome at different levels of the lumbar spine. DSD at levels L1, L5, and S1, and DSR at levels L5 and S1 of patients with proven Marfan syndrome were significantly higher (P < 0.05) than in controls. CONCLUSION: Even during childhood pathologic changes inside the lumbosacral spine of patients with Marfan syndrome can be observed. Dural ectasia, which occurs at different levels of the lumbar spine, can be detected at levels L5 and S1 in up to 40% of patients with Marfan syndrome.

A bioinformatics framework for genotype-phenotype correlation in humans with Marfan syndrome caused by FBN1 gene mutations.

Mutations in the human FBN1 gene are known to be associated with the Marfan syndrome, an autosomal dominant inherited multi-systemic connective tissue disorder. However, in the absence of solid genotype-phenotype correlations, the identification of an FBN1 mutation has only little prognostic value. We propose a bioinformatics framework for the mutated FBN1 gene which comprises the collection, management, and analysis of mutation data identified by molecular genetic analysis (DHPLC) and data of the clinical phenotype. To query our database at different levels of information, a relational data model, describing mutational events at the cDNA and protein levels, and the disease's phenotypic expression from two alternative views, was implemented. For database similarity requests, a query model which uses a distance measure based on log-likelihood weights for each clinical manifestation, was introduced. A data mining strategy for discovering diagnostic markers, classification and clustering of phenotypic expressions was provided which enabled us to confirm some known and to identify some new genotype-phenotype correlations.

Biomarker discovery, disease classification, and similarity query processing on high-throughput MS/MS data of inborn errors of metabolism.

In newborn errors of metabolism, biomarkers are urgently needed for disease screening, diagnosis, and monitoring of therapeutic interventions. This article describes a 2-step approach to discover metabolic markers, which involves (1) the identification of marker candidates and (2) the prioritization of them based on expert knowledge of disease metabolism. For step 1, the authors developed a new algorithm, the biomarker identifier (BMI), to identify markers from quantified diseased versus normal tandem mass spectrometry data sets. BMI produces a ranked list of marker candidates and discards irrelevant metabolites based on a quality measure, taking into account the discriminatory performance, discriminatory space, and variance of metabolites' concentrations at the state of disease. To determine the ability of identified markers to classify subjects, the authors compared the discriminatory performance of several machine-learning paradigms and described a retrieval technique that searches and classifies abnormal metabolic profiles from a screening database. Seven inborn errors of metabolism-- phenylketonuria (PKU), glutaric acidemia type I (GA-I), 3-methylcrotonylglycinemia deficiency (3-MCCD), methylmalonic acidemia (MMA), propionic acidemia (PA), medium-chain acylCoAdehydrogenase deficiency (MCADD), and 3-OH long-chain acyl CoA dehydrogenase deficiency (LCHADD)-were investigated. All primarily prioritized marker candidates could be confirmed by literature. Some novel secondary candidates were identified (i.e., C16:1 and C4DC for PKU, C4DC for GA-I, and C18:1 forMCADD), which require further validation to confirm their biochemical role during health and disease.