Value of serum cystatin C in estimating renal function in children with non-renal solid organ transplantation.

Children with non-renal solid organ transplants are surviving longer, but outcome is complicated by CKD. Accurate and frequent renal function monitoring is imperative to recognize and institute measures early to reverse, prevent, or arrest progression. This study of 59 children determined the accuracy (P30), bias, sensitivity and specificity between measured renal function by NM-GFR, and estimated GFR by three formulas: Filler (serum cystatin C), mSchwartz (serum creatinine), and CKiD (serum cystatin C, creatinine, urea, and height). Mean GFR by all formulas differed significantly from NM-GFR. Filler and mSchwartz formulas significantly increased the proportion of patients with GFR ≥ 90 mL/min/1.73 m(2) (CKD stage 1) while decreasing those with GFR 60-89 mL/min/1.73 m(2) (CKD stage 2). All formulas overestimated GFR. CKiD showed the highest P30 and lowest bias (79.7%; 6.9 mL/min/1.73 m(2) ) followed by Filler (67.7%; 19.9 mL/min/1.73 m(2) ) and Schwartz (57.6%; 26.8 mL/min/1.73 m(2) ) for all GFR values. All formulas performed best with GFR ≥ 90 mL/min/1.73 m(2) , but CKiD was the only formula to achieve 91.1% accuracy. All formulas showed high sensitivities, but low specificities at NM-GFR cutoff at 90. Thus, GFR estimated by CKiD followed by Filler formula is an adequate method to monitor renal function closely and frequently in these children.

Clinical validation of cutoff target ranges in newborn screening of metabolic disorders by tandem mass spectrometry: a worldwide collaborative project.

PURPOSE: To achieve clinical validation of cutoff values for newborn screening by tandem mass spectrometry through a worldwide collaborative effort. METHODS: Cumulative percentiles of amino acids and acylcarnitines in dried blood spots of approximately 25­30 million normal newborns and 10,742 deidentified true positive cases are compared to assign clinical significance, which is achieved when the median of a disorder range is, and usually markedly outside, either the 99th or the 1st percentile of the normal population. The cutoff target ranges of analytes and ratios are then defined as the interval between selected percentiles of the two populations. When overlaps occur, adjustments are made to maximize sensitivity and specificity taking all available factors into consideration. RESULTS: As of December 1, 2010, 130 sites in 45 countries have uploaded a total of 25,114 percentile data points, 565,232 analyte results of true positive cases with 64 conditions, and 5,341 cutoff values. The average rate of submission of true positive cases between December 1, 2008, and December 1, 2010, was 5.1 cases/day. This cumulative evidence generated 91 high and 23 low cutoff target ranges. The overall proportion of cutoff values within the respective target range was 42% (2,269/5,341). CONCLUSION: An unprecedented level of cooperation and collaboration has allowed the objective definition of cutoff target ranges for 114 markers to be applied to newborn screening of rare metabolic disorders.

Perfluorinated acids and hypothyroxinemia in pregnant women.

Perfluorinated acids (PFAs) are prominent and widespread contaminants of human blood. In animal studies there is evidence that suggests certain PFAs can disrupt thyroid hormone homeostasis. A commonly reported condition in exposed animals is hypothyroxinemia, whereby serum free thyroxine (fT4) is decreased despite normal thyroid stimulating hormone (TSH) concentrations. We designed an individually matched case-control study to investigate whether exposure to perfluorooctanoate (PFOA), perfluorohexane sulfonate (PFHxS), and perfluorooctane sulfonate (PFOS) was associated with hypothyroxinemia in pregnant women from Edmonton, Alberta, Canada, in 2005-2006, who underwent a "triple screen" blood test at 15-20 weeks gestation as part of ante-natal care. Thyroid hormones, fT4 and TSH, were measured in serum from 974 women, and from these we measured PFAs in the sera of 96 hypothyroxinemic cases (normal TSH, the lowest 10th percentile of fT4) and 175 controls (normal TSH, fT4 between the 50th and 90th percentiles) matched on age and referring physician. Analyses by conditional logistic regression indicated that the concentrations of PFAs in this population were not associated with hypothyroxinemia among pregnant women. The current findings do not support a causal link between PFA exposure and maternal hypothyroxinemia in the studied population.

Informatics of newborn screening for congenital hypothyroidism in Alberta 2005-08: flow of information from birth to treatment.

OBJECTIVES: Alberta maintains a universal screening program for congenital hypothyroidism, a condition which, when treated promptly prevents neurological impairment. Because the program relies on multiple stakeholders working in different areas, it is not known how effective the overall process is in achieving timely treatment initiation. Our objective was to analyze and describe the informatics of this program. METHODS: Data were collected from the Newborn Metabolic Screening Program and physician offices for hypothyroidism screen positive infants born between january 1, 2005 and May 31, 2008. Where data were available, times were determined for each interval: birth to sample collection, collection to receipt in central laboratory, receipt to report to the primary clinician, report to confirmatory test, and finally confirmation to thyroxin treatment. RESULTS: Complete information was found on the stages up until report generation. Although subsequent intervals had less complete data, all but 5 of the 57 newborns were followed to the endpoint of treatment initiation or diagnosis exclusion. The program was consistent and efficient in collecting, analyzing and reporting results to the primary physician by a median of 8 days (range 4-14 days). Subsequent steps resulted in a median time from birth to treatment of 11 days. There were 4 cases for which delays in clinician follow-up led to treatment initiation at 27, 34, 56 and 70 days. CONCLUSION: Newborn screening for congenital hypothyroidism in Alberta is efficient and consistent up until responsibility shifts to the community. Quality improvement work is needed to reduce potential delays.

Carnitine palmitoyltransferase 1A (CPT1A) P479L prevalence in live newborns in Yukon, Northwest Territories, and Nunavut.

Carnitine palmitoyltransferase 1A (CPT1A), encoded by the gene CPT1A, is the hepatic isoform of CPT1 and is a major regulatory point in long-chain fatty acid oxidation. CPT1A deficiency confers risk for hypoketotic hypoglycaemia, hepatic encephalopathy, seizures, and sudden unexpected death in infancy (SUDI). It remains controversial whether the CPT1A gene variant, c.1436C>T (p.P479L), identified in Inuit, First Nations, and Alaska Native infants, causes susceptibility to decompensation, in particular during times of fever and intercurrent illness. Although newborn screening for the P479L variant occurs in some jurisdictions, background knowledge about the presence of the variant in Canadian Aboriginal populations is lacking. In an effort to understand the population implications of the variant in northern Canada, overall frequencies of the variant were assessed. Further studies are underway to determine associated risk. Ethics approval was obtained from university REBs, local research institutes, and with consultation with territorial Aboriginal groups. Newborn screening blood spots from all infants born in 2006 in the three territories were genotyped for the p.P479L variant. p.P479L (c.1436C>T) allele frequencies in the three territories were 0.02, 0.08, and 0.77 in Yukon (n=325), Northwest Territories (n=564), and Nunavut (n=695), respectively. Homozygosity rates were 0%, 3%, and 64%. Aboriginal status was available only in NWT, with allele frequencies of 0.04, 0.44, 0.00, and 0.01 for First Nations, Inuvialuit/Inuit, Métis, and non-Aboriginal populations. Although individual blood spots were not identified for Aboriginal ethnicity in Nunavut infants, ~90% of infants in Nunavut are born to Inuit women. The allele frequency and rate of homozygosity for the CPT1A P479L variant were high in Inuit and Inuvialuit who reside in northern coastal regions. The variant is present at a low frequency in First Nations populations, who reside in areas less coastal than the Inuit or Inuvialuit in the two western territories. The significance of the population and geographic distribution remains unclear, but the high population frequencies of the variant suggest a historically low penetrance for adverse outcomes. Further evidence is needed to determine if there is an increased risk for infant mortality and morbidity and whether newborn screening will be indicated on a population basis.

Maternal thyroid hormones in early pregnancy and risk of breech presentation.

OBJECTIVE: To evaluate the relationship between breech presentation at term (>/= 37 weeks of gestation) and maternal thyroid hormone activity in early gestation. METHODS: We conducted a case-control study of thyroid hormone activity in 179 women who delivered a live term infant in breech presentation (cases) and 849 women who delivered a live term infant in cephalic presentation (control subjects). We used serum samples from prenatal screening at 15 to 16 weeks of gestation in 2006 and 2007 in Edmonton, Alberta. Maternal free thyroxin (fT4) and thyroid-stimulating hormone (TSH) were assayed. Logistic regression was used to estimate the odds of breech presentation in relation to the levels of thyroid hormones while controlling for potential confounders. RESULTS: There were no significant differences between the breech and cephalic groups when comparing fT4 levels (OR 0.94 per pmol/L; 95% CI 0.88 to 1.00) or TSH levels (OR 1.16 per mU/L; 95% CI 0.97 to 1.38) levels, after adjustment for all potential confounders. Segregating fT4 and TSH into quintiles showed the same pattern. Neither hypothyroidism nor hyperthyroidism was associated with risk of breech presentation. CONCLUSION: Our results provide evidence that maternal thyroid hormone levels at 15 to 16 weeks of gestation are not related to risk of breech presentation at birth in term infants.

Evaluation of the accuracy of self-reported smoking in pregnancy when the biomarker level in an active smoker is uncertain.

INTRODUCTION: Our main objective was to estimate smoking prevalence as well as sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of self-reported smoking among pregnant women in Edmonton, Canada, at 15-16 weeks of gestation. METHODS: We used serum samples to assemble a cohort of pregnant women who underwent an optional second-trimester screening for chromosomal and developmental anomalies. We determined cotinine concentrations for 92 self-reported smokers (11% of the cohort) and for 285 self-reported nonsmoking mothers, using adapted urinary cotinine assay. Self-reports were collected at the time of delivery. In a validation study, serum cotinine was determined for known smokers and nonsmokers and used, within a Bayesian statistical framework, to define the distribution of cutoffs that differentiate true smokers from nonsmokers. This distribution of cutoffs was used to construct multiple two-by-two tables to obtain the distribution of sensitivity, specificity, PPV, NPV, and prevalence. RESULTS: Sensitivity was poor (M = 47.4%, SD = 17.3%), but specificity was nearly perfect (M = 94.9%, SD = 1.1%). PPV (M = 66.6%, SD = 11.7%) was smaller than NPV (M = 84.7%, SD = 14.3%). In our sample, the prevalence of true smoking at 15-16 weeks of gestation was described by a skewed distribution with a mean of 21.6% (SD = 13.8%) and a median of 16.6%. DISCUSSION: The strength of the present study includes blinding of subjects to the intention to test their sera for a biomarker of smoking. A limitation was the use of a nonrandom sample restricted to pregnancies that resulted in live births. We discuss data collection methods that would elicit more accurate smoking histories from pregnant women.

HMDB: the Human Metabolome Database.

The Human Metabolome Database (HMDB) is currently the most complete and comprehensive curated collection of human metabolite and human metabolism data in the world. It contains records for more than 2180 endogenous metabolites with information gathered from thousands of books, journal articles and electronic databases. In addition to its comprehensive literature-derived data, the HMDB also contains an extensive collection of experimental metabolite concentration data compiled from hundreds of mass spectra (MS) and Nuclear Magnetic resonance (NMR) metabolomic analyses performed on urine, blood and cerebrospinal fluid samples. This is further supplemented with thousands of NMR and MS spectra collected on purified, reference metabolites. Each metabolite entry in the HMDB contains an average of 90 separate data fields including a comprehensive compound description, names and synonyms, structural information, physico-chemical data, reference NMR and MS spectra, biofluid concentrations, disease associations, pathway information, enzyme data, gene sequence data, SNP and mutation data as well as extensive links to images, references and other public databases. Extensive searching, relational querying and data browsing tools are also provided. The HMDB is designed to address the broad needs of biochemists, clinical chemists, physicians, medical geneticists, nutritionists and members of the metabolomics community. The HMDB is available at: www.hmdb.ca.

The impact of isolated maternal hypothyroxinemia on perinatal morbidity.

OBJECTIVE: To determine whether maternal hypothyroxinemia during early pregnancy is associated with adverse perinatal outcomes. METHODS: Serum samples of a prospective cohort of 879 women collected at 15-16 weeks of pregnancy were analyzed for thyroid-stimulating hormone (TSH) and free thyroxine (T4) concentrations. Women with TSH levels within the normal reference range (0.15-4.0 mU/L) and free T4 levels below the 10th percentile of the sample (8.5 pmol/L) were classified as hypothyroxinemic and were compared with euthyroid women (who had normal TSH and free T4 levels). Thyroid hormone measures were linked to pregnancy outcomes, including small for gestational age (SGA), standardized birth weight z-score, preterm delivery, and Apgar score used as a measure of early neonatal morbidity. RESULTS: Among 89 hypothyroxinemic women, there was no evidence of an increased risk for fetal growth restriction, preterm birth, or low Apgar score. The relative risk of delivering an SGA infant was 0.38 (95% CI 0.11 to 1.33), the mean difference in birth weight z-score was 0.035 (95% CI -0.17 to 0.24), and the risk of preterm delivery was 0.79 (95% CI 0.38 to 1.67). None of the hypothyroxinemic women gave birth to an infant with a five-minute Apgar score <7. When free T4 levels were substituted for categories of thyroid hormone function, the pattern of results remained unaltered. CONCLUSION: Isolated maternal hypothyroxinemia was not observed to have any adverse effect on fetal growth or pregnancy outcome. This study does not provide evidence to support treatment of this condition to prevent fetal growth restriction or neonatal morbidity.

The human cerebrospinal fluid metabolome.

With continuing improvements in analytical technology and an increased interest in comprehensive metabolic profiling of biofluids and tissues, there is a growing need to develop comprehensive reference resources for certain clinically important biofluids, such as blood, urine and cerebrospinal fluid (CSF). As part of our effort to systematically characterize the human metabolome we have chosen to characterize CSF as the first biofluid to be intensively scrutinized. In doing so, we combined comprehensive NMR, gas chromatography-mass spectrometry (GC-MS) and liquid chromatography (LC) Fourier transform-mass spectrometry (FTMS) methods with computer-aided literature mining to identify and quantify essentially all of the metabolites that can be commonly detected (with today's technology) in the human CSF metabolome. Tables containing the compounds, concentrations, spectra, protocols and links to disease associations that we have found for the human CSF metabolome are freely available at http://www.csfmetabolome.ca.

Biochemistry testing associated with pregnancy and the newborn period -- a lot has changed since you were a baby!

Everyone has been a newborn, and everyone's mother has been pregnant. Despite the commonality of these events, medical care and the clinical chemistry laboratory's role in it have changed remarkably over the last 50 years. This review is a historical overview of clinical chemistry testing that is related to pregnancy and the newborn period.

Incomplete pediatric reference intervals for the management of patients with inborn errors of metabolism.

OBJECTIVES: To evaluate the status of pediatric reference intervals for several biomarkers of inborn errors of metabolism (IEM). INTRODUCTION: There are several biomarkers that are used in many laboratories that specialize in biochemical genetics. Among them, there are acylcarnitines, total carnitine, amino acids, essential fatty acids, phytanic acid and very long chain fatty acids. These tests are key to exclusion or inclusion of an IEM, therefore appropriate age-related references intervals are crucial. A detailed review of each selected analyte is given. RESULTS: Published reference intervals do not always address the dependency of age, gender, or ethnic background; they are not established for newer laboratory methodologies and are derived from a limited number of healthy controls for most markers. CONCLUSIONS: To address the gap in pediatric reference intervals, the Canadian research project (CALIPER database) will establish comprehensive reference intervals for acylcarnitines, total carnitine, amino acids, essential fatty acids, phytanic acid, and very long chain fatty acids. All the tests will be limited to whole blood, plasma and serum samples.

B-type natriuretic peptide in pediatrics.

OBJECTIVES: There has been growing interest in the use of serum B-type natriuretic peptide (BNP) and the N-terminal segment of its pro-hormone (NT-proBNP) as biomarkers for cardiac disease. The aim of this review is to summarize the current state of knowledge regarding BNP and NT-proBNP measurement in the pediatric population. DESIGN AND METHODS: A computerized literature search on the National Library of Medicine was done and all articles including BNP and pediatrics were selected and discussed. RESULTS: The data from several studies suggest that the measurement of BNP may be useful in diagnosing and managing pediatric heart failure, congenital heart disease, cardiac transplantation and patients on chemotherapy. There are difficulties in establishing appropriate reference ranges in children. CONCLUSION: There is insufficient evidence for the routine use of BNP or NT-proBNP. Further research to clearly define the clinical utility in the pediatric age group is eagerly anticipated.

Mild elevation of N-acetylaspartic acid and macrocephaly: diagnostic problem.

Patients with slightly increased excretion of N-acetylaspartic acid in urine, together with macrocephaly, present a dignostic dilemma for Canavan's disease. We describe a 13-year-old male patient with macrocephaly, mild developmental delay, increased signal intensity in the basal ganglia bilaterally, partial cortical blindness, and retinitis pigmentosa. Although the clinical course and magnetic resonance imaging findings did not resemble typical Canavan's disease, N-acetylaspartic acid excretion in the patient's urine was slightly elevated, 99.90 +/- 4.00 microg/mg creatinine, whereas the normal control range was < 83 microg/mg creatinine. Cultured skin fibroblasts from the patient showed no aspartoacylase activity. Cloning of genomic DNA isolated from the patient's fibroblasts showed an intronic mutation, specifically deletion of -2A and -3C at the acceptor site of exon 3 and disrupting the normal splicing of the gene. A second mutation was found in exon 6, 863 A-->G in aspartoacylase complementary DNA, causing a tyrosine-to-cysteine (Y288C) amino acid substitution. Expression of the mutation on exon 6 showed normal aspartoacylase activity. These data suggest that expression of the mutation may help to understand the enzyme defect in a patient with slightly increased N-acetylaspartic acid excretion.

Mitochondriome and cholangiocellular carcinoma.

Cholangiocellular carcinoma (CCA) of the liver was the target of more interest, recently, due mainly to its increased incidence and possible association to new environmental factors. Somatic mitochondrial DNA (mtDNA) mutations have been found in several cancers. Some of these malignancies contain changes of mtDNA, which are not or, very rarely, found in the mtDNA databases. In terms of evolutionary genetics and oncology, these data are extremely interesting and may be considered a sign of poor fitness, which may conduct in some way to different cellular processes, including carcinogenesis. MitoChip analysis is a strong tool for investigations in experimental oncology and was carried out on three CCA cell lines (HuCCT1, Huh-28 and OZ) with different outcome in human and a Papova-immortalized normal hepatocyte cell line (THLE-3). Real time quantitative PCR, western blot analysis, transmission electron microscopy, confocal laser microscopy, and metabolic assays including L-Lactate and NAD+/NADH assays were meticulously used to identify mtDNA copy number, oxidative phosphorylation (OXPHOS) content, ultrastructural morphology, mitochondrial membrane potential (ΔΨm), and differential composition of metabolites, respectively. Among 102 mtDNA changes observed in the CCA cell lines, 28 were non-synonymous coding region alterations resulting in an amino acid change. Thirty-eight were synonymous and 30 involved ribosomal RNA (rRNA) and transfer RNA (tRNA) regions. We found three new heteroplasmic mutations in two CCA cell lines (HuCCT1 and Huh-28). Interestingly, mtDNA copy number was decreased in all three CCA cell lines, while complexes I and III were decreased with depolarization of mitochondria. L-Lactate and NAD+/NADH assays were increased in all three CCA cell lines. MtDNA alterations seem to be a common event in CCA. This is the first study using MitoChip analysis with comprehensive metabolic studies in CCA cell lines potentially creating a platform for future studies on the interactions between normal and neoplastic cells.

Maternal exposure to bisphenol-A and fetal growth restriction: a case-referent study.

We conducted a case-referent study of the effect of exposure to bisphenol-A on fetal growth in utero in full-term, live-born singletons in Alberta, Canada. Newborns <10 percentile of expected weight for gestational age and sex were individually matched on sex, maternal smoking and maternal age to referents with weight appropriate to gestational age. Exposure of the fetus to bisphenol-A was estimated from maternal serum collected at 15-16 weeks of gestation. We pooled sera across subjects for exposure assessment, stratified on case-referent status and sex. Individual 1:1 matching was maintained in assembling 69 case and 69 referent pools created from 550 case-referent pairs. Matched pools had an equal number of aliquots from individual women. We used an analytical strategy conditioning on matched set and total pool-level values of covariates to estimate individual-level effects. Pools of cases and referents had identical geometric mean bisphenol-A concentrations (0.5 ng/mL) and similar geometric standard deviations (2.3-2.5). Mean difference in concentration between matched pools was 0 ng/mL, standard deviation: 1 ng/mL. Stratification by sex and control for confounding did not suggest bisphenol-A increased fetal growth restriction. Our analysis does not provide evidence to support the hypothesis that bisphenol-A contributes to fetal growth restriction in full-term singletons.

Mitochondrial DNA related cardiomyopathies.

Cardiomyopathies are a heterogeneous group of diseases characterized by impaired heart muscle function. Over the last few years, interest in mitochondrial cardiomyopathies has been galvanized by a number of significant molecular biology discoveries. There is overwhelming evidence that genetic factors play a pivotal role in the pathogenesis of primary cardiomyopathies. Mitochondrial cardiomyopathy is a cardiomyopathy in which the clinical and pathological phenotype result from mitochondrial diseases due to pathogenic mutation in both mitochondrial and/or nuclear genes causing defects in the oxidative phosphorylation system (OXPHOS) in cardiac muscle. We review and provide an update of the current concepts, molecular genetics, clinical features, pathology, diagnostic modalities, and latest therapeutic options in mitochondrial cardiomyopathies specifically caused by mutations in the mitochondrial DNA (mtDNA).

Multifaceted support for a new medical school in Nepal devoted to rural health by a Canadian Faculty of Medicine and Dentistry.

Nepal and Alberta are literally a world apart. Yet they share a common problem of restricted access to health services in remote and rural areas. In Nepal, urban-rural disparities were one of the main issues in the recent civil war, which ended in 2006. In response to the need for improved health equity in Nepal a dedicated group of Nepali physicians began planning the Patan Academy of Health Sciences (PAHS), a new health sciences university dedicated to the education of rural health providers in the early 2000s. Beginning with a medical school the Patan Academy of Health Sciences uses international help to plan, deliver and assess its curriculum. PAHS developed an International Advisory Board (IAB) attracting international help using a model of broad, intentional recruitment and then on individuals' natural attraction to a clear mission of peace-making through health equity. Such a model provides for flexible recruitment of globally diverse experts, though it risks a lack of coordination. Until recently, the PAHS IAB has not enjoyed significant or formal support from any single international institution. However, an increasing number of the international consultants recruited by PAHS to its International Advisory Board are from the University of Alberta in Edmonton, Alberta, Canada (UAlberta). The number of UAlberta Faculty of Medicine and Dentistry members involved in the project has risen to fifteen, providing a critical mass for a coordinated effort to leverage institutional support for this partnership. This paper describes the organic growth of the UAlberta group supporting PAHS, and the ways in which it supports a sister institution in a developing nation.

Qualitative metabolome analysis of human cerebrospinal fluid by 13C-/12C-isotope dansylation labeling combined with liquid chromatography Fourier transform ion cyclotron resonance mass spectrometry.

Metabolome analysis of human cerebrospinal fluid (CSF) is challenging because of low abundance of metabolites present in a small volume of sample. We describe and apply a sensitive isotope labeling LC-MS technique for qualitative analysis of the CSF metabolome. After a CSF sample is divided into two aliquots, they are labeled by (13)C-dansyl and (12)C-dansyl chloride, respectively. The differentially labeled aliquots are then mixed and subjected to LC-MS using Fourier-transform ion cyclotron resonance mass spectrometry (FTICR MS). Dansylation offers significant improvement in the performance of chromatography separation and detection sensitivity. Moreover, peaks detected in the mass spectra can be readily analyzed for ion pair recognition and database search based on accurate mass and/or retention time information. It is shown that about 14,000 features can be detected in a 25-min LC-FTICR MS run of a dansyl-labeled CSF sample, from which about 500 metabolites can be profiled. Results from four CSF samples are compared to gauge the detectability of metabolites by this method. About 261 metabolites are commonly detected in replicate runs of four samples. In total, 1132 unique metabolite ion pairs are detected and 347 pairs (31%) matched with at least one metabolite in the Human Metabolome Database. We also report a dansylation library of 220 standard compounds and, using this library, about 85 metabolites can be positively identified. Among them, 21 metabolites have never been reported to be associated with CSF. These results illustrate that the dansylation LC-FTICR MS method can be used to analyze the CSF metabolome in a more comprehensive manner.

The human serum metabolome.

Continuing improvements in analytical technology along with an increased interest in performing comprehensive, quantitative metabolic profiling, is leading to increased interest pressures within the metabolomics community to develop centralized metabolite reference resources for certain clinically important biofluids, such as cerebrospinal fluid, urine and blood. As part of an ongoing effort to systematically characterize the human metabolome through the Human Metabolome Project, we have undertaken the task of characterizing the human serum metabolome. In doing so, we have combined targeted and non-targeted NMR, GC-MS and LC-MS methods with computer-aided literature mining to identify and quantify a comprehensive, if not absolutely complete, set of metabolites commonly detected and quantified (with today's technology) in the human serum metabolome. Our use of multiple metabolomics platforms and technologies allowed us to substantially enhance the level of metabolome coverage while critically assessing the relative strengths and weaknesses of these platforms or technologies. Tables containing the complete set of 4229 confirmed and highly probable human serum compounds, their concentrations, related literature references and links to their known disease associations are freely available at http://www.serummetabolome.ca.