Chemistry RSS : Gourt

Adiponectin and Prostate Cancer Mortality: To Be or Not to Be Skinny? [Editorials]

Few Point-of-Care Hemoglobin A1c Assay Methods Meet Clinical Needs [Editorials]

Use of Cerebrospinal Fluid Biomarkers for Diagnosis of Incipient Alzheimer Disease in Patients with Mild Cognitive Impairment [Perspective]

Detection of Biological Agents Used for Terrorism: Are We Ready? [Q[amp ]A]

Sharply Increased Serum Free Light-Chain Concentrations after Treatment for Multiple Myeloma [Clinical Case Study]

Commentary [Clinical Case Study]

Stroke Biomarkers: Progress and Challenges for Diagnosis, Prognosis, Differentiation, and Treatment [Review]

Background: Stroke is a devastating condition encompassing a wide range of pathophysiological entities that include thrombosis, hemorrhage, and embolism. Current diagnosis of stroke relies on physician clinical examination and is further supplemented with various neuroimaging techniques. A single set or multiple sets of blood biomarkers that could be used in an acute setting to diagnosis stroke, differentiate between stroke types, or even predict an initial/reoccurring stroke would be extremely valuable. Content: We discuss the current classification, diagnosis, and treatment of stroke, focusing on use of novel biomarkers (either solitary markers or multiple markers within a panel) that have been studied in a variety of clinical settings. Summary: The current diagnosis of stroke remains hampered and delayed due to lack of a suitable mechanism for rapid (ideally point-of-care), accurate, and analytically sensitive biomarker-based testing. There is a clear need for further development and translational research in this area. Potential biomarkers identified need to be transitioned quickly into clinical validation testing for further evaluation in an acute stroke setting; to do so would impact and improve patient outcomes and quality of life.

A 25-Year Prospective Study of Plasma Adiponectin and Leptin Concentrations and Prostate Cancer Risk and Survival [Endocrinology and Metabolism]

Background: Adipocytokines may mediate the association between adiposity and lethal prostate cancer outcomes. Methods: In the Physicians’ Health Study, we prospectively examined the association of prediagnostic plasma concentrations of adiponectin and leptin with risk of developing incident prostate cancer (654 cases diagnosed 1982–2000 and 644 age-matched controls) and, among cases, risk of dying from prostate cancer by 2007. Results: Adiponectin concentrations were not associated with risk of overall prostate cancer. However, men with higher adiponectin concentrations had lower risk of developing high-grade or lethal cancer (metastatic or fatal disease). The relative risk (95% CI) comparing the highest quintile to the lowest (Q5 vs Q1) was 0.25 (95% CI 0.07–0.87; Ptrend = 0.02) for lethal cancer. Among all the cases, higher adiponectin concentrations predicted lower prostate cancer–specific mortality [hazard ratio (HR)Q5 vs Q1= 0.39; 95% CI 0.17–0.85; Ptrend = 0.02], independent of body mass index (BMI), plasma C-peptide (a marker of insulin secretion), leptin, clinical stage, and tumor grade. This inverse association was apparent mainly among men with a BMI ≥25 kg/m2 (HRQ5 vs Q1= 0.10; 95% CI 0.01–0.78; Ptrend = 0.02), but not among men of normal weight (Ptrend = 0.51). Although the correlation of leptin concentrations with BMI (r = 0.58, P < 0.001) was stronger than that of adiponectin (r = –0.17, P < 0.001), leptin was unrelated to prostate cancer risk or mortality. Conclusions: Higher prediagnostic adiponectin (but not leptin) concentrations predispose men to a lower risk of developing high-grade prostate cancer and a lower risk of subsequently dying from the cancer, suggesting a mechanistic link between obesity and poor prostate cancer outcome.

Six of Eight Hemoglobin A1c Point-of-Care Instruments Do Not Meet the General Accepted Analytical Performance Criteria [Point-of-Care Testing]

Background: Hemoglobin A1c (Hb A1c) point-of-care (POC) instruments are widely used to provide rapid-turnaround results in diabetic care centers. We investigated the conformance of various Hb A1c POC instruments (In2it from Bio-Rad, DCA Vantage from Siemens, Afinion and Nycocard from Axis-Shield, Clover from Infopia, InnovaStar from DiaSys, A1CNow from Bayer, and Quo-Test from Quotient Diagnostics) with generally accepted performance criteria for Hb A1c. Methods: The CLSI protocols EP-10, EP-5, and EP-9 were applied to investigate imprecision, accuracy, and bias. We assessed bias using 3 certified secondary reference measurement procedures and the mean of the 3 reference methods. Assay conformance with the National Glycohemoglobin Standardization Program (NGSP) certification criteria, as calculated from analyses with 2 different reagent lot numbers for each Hb A1c method, was also evaluated. Results: Because of disappointing EP-10 results, 2 of the 8 manufacturers decided not to continue the evaluation. The total CVs from EP-5 evaluations for the different instruments with a low and high Hb A1c value were: In2it 4.9% and 3.3%, DCA Vantage 1.8% and 3.7%, Clover 4.0% and 3.5%, InnovaStar 3.2% and 3.9%, Nycocard 4.8% and 5.2%, and Afinion 2.4% and 1.8%. Only the Afinion and the DCA Vantage passed the NGSP criteria with 2 different reagent lot numbers. Conclusions: Only the Afinion and the DCA Vantage met the acceptance criteria of having a total CV <3% in the clinically relevant range. The EP-9 results and the calculations of the NGSP certification showed significant differences in analytical performance between different reagent lot numbers for all Hb A1c POC instruments.

Alternative Splicing and Molecular Characterization of Splice Site Variants: BRCA1 c.591C>T as a Case Study [Molecular Diagnostics and Genetics]

Background: Deleterious mutations in BRCA1 (breast cancer 1, early onset; MIM 113705) increase breast and ovarian cancer [B(O)C] risk; however, many variants cannot be readily classified as deleterious or neutral. Unclassified variants (UVs) pose serious problems in genetic counseling. RNA-splicing analysis is essential for the assessment of many UVs. Methods: Denaturing gradient gel electrophoresis was used to genotype the BRCA1 c.591C>T variant in 685 index cases of B(O)C families, 326 sporadic breast cancer cases, and 450 healthy controls from Spain. In silico tools were used to predict the effect of the c.591C>T variant on splicing. In vitro splicing analysis was performed in 7 c.591C>T carriers and 10 noncarriers. cDNAs were PCR-amplified with primers designed to detect BRCA1 alternative splicing isoforms. The products were analyzed by capillary electrophoresis. Peak areas were used to quantify the relative abundance of each isoform. Sequencing through exonic single-nucleotide polymorphisms (SNPs) enabled us to discriminate wild-type and variant transcripts. Results: c.591C>T was detected in B(O)C families (1.5%), breast cancer cases (0.3%), and controls (0.9%). c.591C>T induced BRCA1 exon 9 skipping and modified the relative expression of (9,10), (9,10,11B), 11B, and full-length isoforms. The mean ratio of (9,10) to the full-length isoform increased from 0.25 in noncarriers to 1.5 in carriers. The mean (9,10,11B)/11B ratio increased from 0.2 to 4. Overall expression levels of c.591C>T and wild-type alleles were similar. Conclusions: Our data support a nonpathogenic role for the BRCA1 c.591C>T variant. Naturally occurring alternative splicing isoforms need to be considered when assessing the role of BRCA1 UVs on splicing.

DNA Sequence Capture and Enrichment by Microarray Followed by Next-Generation Sequencing for Targeted Resequencing: Neurofibromatosis Type 1 Gene as a Model [Molecular Diagnostics and Genetics]

Background: The introduction and use of next-generation sequencing (NGS) techniques have taken genomic research into a new era; however, implementing such powerful techniques in diagnostics laboratories for applications such as resequencing of targeted disease genes requires attention to technical issues, including sequencing template enrichment, management of massive data, and high interference by homologous sequences. Methods: In this study, we investigated a process for enriching DNA samples that uses a customized high-density oligonucleotide microarray to enrich a targeted 280-kb region of the NF1 (neurofibromin 1) gene. The captured DNA was sequenced with the Roche/454 GS FLX system. Two NF1 samples (CN1 and CN2) with known genotypes were tested with this protocol. Results: Targeted microarray capture may also capture sequences from nontargeted regions in the genome. The capture specificity estimated for the targeted NF1 region was approximately 60%. The de novo Alu insertion was partially detected in sample CN1 by additional de novo assembly with 50% base-match stringency; the single-base deletion in sample CN2 was successfully detected by reference mapping. Interferences by pseudogene sequences were removed by means of dual-mode reference-mapping analysis, which reduced the risk of generating false-positive data. The risk of generating false-negative data was minimized with higher sequence coverage (>30x). Conclusions: We used a clinically relevant complex genomic target to evaluate a microarray-based sample-enrichment process and an NGS instrument for clinical resequencing purposes. The results allowed us to develop a systematic data-analysis strategy and algorithm to fit potential clinical applications.

Synergy of Total PLAC4 RNA Concentration and Measurement of the RNA Single-Nucleotide Polymorphism Allelic Ratio for the Noninvasive Prenatal Detection of Trisomy 21 [Molecular Diagnostics and Genetics]

Background: Maternal plasma mRNA encoded by the PLAC4 gene (placenta-specific 4), which is transcribed from chromosome 21 in placental cells, is a potential marker for the noninvasive assessment of chromosome 21 dosage in the fetus. We evaluated the diagnostic sensitivities and specificities of 2 trisomy 21–screening approaches that use maternal plasma PLAC4 mRNA. Methods: We studied maternal plasma samples from 153 pregnant women carrying euploid and trisomy 21 fetuses. For the samples in which the fetuses were heterozygous for the studied PLAC4 single-nucleotide polymorphism (SNP), we measured the ratio between 2 alleles of the SNP in maternal plasma PLAC4 mRNA (RNA-SNP) by mass spectrometric (MS) and digital PCR methods. For pregnancies involving fetuses homozygous for the SNP, we quantified the total PLAC4 mRNA concentration in maternal plasma by real-time PCR and digital PCR. Results: For the RNA-SNP approach, we achieved a diagnostic sensitivity and specificity of 100% (95% CI, 40.2%–100%) and 89.7% (95% CI, 78.8%–96.1%), respectively, for both the MS and the digital PCR methods. For the mRNA-quantification approach, the areas under the ROC curves were 0.859 (95% CI, 0.741–0.903) and 0.833 (95% CI, 0.770–0.923) for plasma PLAC4 mRNA concentrations measured by the real-time PCR and the digital PCR methods, respectively. Conclusions: For prenatal screening of trisomy 21, the quantification of the total PLAC4 mRNA concentration can be used in a synergistic manner with the RNA-SNP allelic ratio approach to increase the population coverage of cases in which diagnostic information can be obtained.

Aberrant Concentrations of Liver-Derived Plasma Albumin mRNA in Liver Pathologies [Molecular Diagnostics and Genetics]

Background: We hypothesized that liver-derived mRNA, such as ALB (albumin) mRNA, would be released into human plasma with liver cell death. Methods: We genotyped ALB mRNA molecules in samples of plasma and whole blood from liver and bone marrow transplant recipients by RNA single-nucleotide polymorphism analysis. Plasma and whole blood ALB mRNA genotypes were compared with the DNA genotypes of the recipients and donors. A reverse-transcription quantitative real-time PCR assay was used to measure plasma ALB mRNA concentrations in 107 patients [hepatocellular carcinoma (HCC), cirrhosis, or chronic hepatitis B (CHB)] and 207 healthy controls. Results: The RNA genotype data revealed ALB mRNA in plasma to be liver derived, whereas tissue compartments other than the liver also contributed to the ALB mRNA detected in whole blood. Statistically significant increases in plasma ALB mRNA concentrations were observed for HCC, cirrhosis, and active CHB, compared with controls. A cutoff of 835 copies/mL of plasma ALB mRNA identified by ROC curve analysis showed 85.5% diagnostic sensitivity and 92.8% diagnostic specificity for the detection of liver pathologies. Only 21.5% of patients with liver pathologies had increased alanine aminotransferase (ALT) activities, whereas 73.8% had increased plasma ALB mRNA concentrations. Only 48.6% of the HCC patients had increased serum -fetoprotein concentrations, whereas 91.4% had increased plasma ALB mRNA concentrations. Conclusions: ALB mRNA is liver specific in plasma, but not in whole blood. Plasma ALB mRNA is increased in some liver pathologies and may be more diagnostically sensitive than -fetoprotein and ALT.

Noninvasive Prenatal Detection of Trisomy 21 by an Epigenetic-Genetic Chromosome-Dosage Approach [Molecular Diagnostics and Genetics]

Background: The use of fetal DNA in maternal plasma for noninvasive prenatal diagnosis of trisomy 21 (T21) is an actively researched area. We propose a novel method of T21 detection that combines fetal-specific epigenetic and genetic markers. Methods: We used combined bisulfite restriction analysis to search for fetal DNA markers on chromosome 21 that were differentially methylated in the placenta and maternal blood cells and confirmed any target locus with bisulfite sequencing. We then used methylation-sensitive restriction endonuclease digestion followed by microfluidics digital PCR analysis to investigate the identified marker. Chromosome-dosage analysis was performed by comparing the dosage of this epigenetic marker with that of the ZFY (zinc finger protein, Y-linked) gene on chromosome Y. Results: The putative promoter of the HLCS (holocarboxylase synthetase) gene was hypermethylated in the placenta and hypomethylated in maternal blood cells. A chromosome-dosage comparison of the hypermethylated HLCS and ZFY loci could distinguish samples of T21 and euploid placental DNA. Twenty-four maternal plasma samples from euploid pregnancies and 5 maternal plasma samples from T21 pregnancies were analyzed. All but 1 of the euploid samples were correctly classified. Conclusions: The epigenetic–genetic chromosome-dosage approach is a new method for noninvasive prenatal detection of T21. The epigenetic part of the analysis can be applied to all pregnancies. Because the genetic part of the analysis uses paternally inherited, fetal-specific genetic markers that are abundant in the genome, broad population coverage should be readily achievable. This approach has the potential to become a generally usable technique for noninvasive prenatal diagnosis.

Bright-Field Microscopy Visualization of Proteins and Protein Complexes by In Situ Proximity Ligation with Peroxidase Detection [Molecular Diagnostics and Genetics]

Background: The in situ proximity ligation assay (PLA) allows a protein or protein complex to be represented as an amplifiable DNA molecule. Recognition is mediated by proximity probes consisting of antibodies coupled with oligonucleotides. Upon dual binding of the proximity probes, the oligonucleotides direct the formation of a circular DNA molecule, which is then amplified by rolling-circle replication. The localized concatemeric product is then detected with fluorescent probes. The in situ PLA enables localized detection of individual native proteins or interacting protein pairs in fixed cells or tissue sections, thus providing an important tool for basic and clinical research. Methods: We used horseradish peroxidase (HRP)-conjugated oligonucleotides to couple in situ PLA with enzymatic visualization of the localized detection event. Results: We demonstrate the detection of protein complexes, both in cells and in tissue sections, and show that we can quantify the complexes with image-analysis software specially developed for recognizing HRP signals in bright-field microscopy images. We show that fluorescence and HRP signals produce equivalent results, both in cultured cells and in tissue samples. Conclusions: The combination of in situ PLA with bright-field detection and automated image analysis allows the signals present to be counted in an automated fashion and thus provides a sensitive and specific method for quantification of proteins and protein complexes with bright-field microscopy. With this approach, in situ PLA can be used without the requirement for expensive fluorescence microscopes, thereby avoiding problems with nonspecific fluorescence while maintaining compatibility with conventional histologic staining.

Distribution of Asymmetric Dimethylarginine among 980 Healthy, Older Adults of Different Ethnicities [Lipids, Lipoproteins, and Cardiovascular Risk Factors]

Background: Endothelium-derived nitric oxide plays a crucial role in the regulation of vascular tone and the development of cardiovascular disease. The endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) has emerged as a novel cardiovascular risk factor. ADMA appears to be an independent predictor for cardiovascular and overall mortality. However, the majority of studies investigating the clinical role of ADMA were performed in European study populations with few individuals of other ethnicities. Methods: We performed a cross-sectional study of 980 healthy, older (age 60–72 years) individuals of different ethnicities living in the San Francisco Bay area and analyzed ADMA plasma concentrations and their relationship to other cardiovascular risk factors. Plasma ADMA concentrations were measured using a recently developed, highly sensitive ELISA. Results: In our entire sample, we were able to define a reference interval for ADMA plasma concentrations of 0.47 (90% CI 0.46–0.48) µmol/L to 0.85 (0.84–0.89) µmol/L. The mean ADMA concentration was 0.63 (SD 0.11) µmol/L (median 0.61 µmol/L). Mean ADMA concentrations were significantly lower in African Americans (0.60 µmol/L; P < 0.01) and mixed non-Hispanics (0.60 µmol/L; P < 0.05) compared with whites (0.63 µmol/L). ADMA was positively correlated with cystatin-C in both men ( = 0.29) and women ( = 0.37), and median plasma ADMA concentrations increased across cystatin-C quintiles. Conclusions: ADMA varies nearly 2-fold across a healthy sample of older men and women, correlates with age, body mass index, and renal function, and is different across ethnic groups. Additional studies in a wider age range and including larger ethnic subgroups would be useful.

Prognostic Value of Emerging Neurohormones in Chronic Heart Failure during Optimization of Heart Failure-Specific Therapy [Proteomics and Protein Markers]

Background: Serial measurements of neurohormones have been shown to improve prognostication in the setting of acute heart failure (HF) or chronic HF without therapeutic intervention. We investigated the prognostic role of serial measurements of emerging neurohormones and BNP in a cohort of chronic HF patients undergoing increases in HF-specific therapy. Methods: In this prospective study we included 181 patients with chronic systolic HF after an episode of hospitalization for worsening HF. Subsequently, HF therapy was gradually increased in the outpatient setting until optimized. We measured copeptin, midregional proadrenomedullin, C-terminal endothelin-1 precursor fragment, midregional proatrial natriuretic peptide, and B-type natriuretic peptide before and after optimization of HF therapy. The primary endpoint was all-cause mortality at 24 months. Results: Angiotensin-converting enzyme/angiotensin receptor blocker and β-blockers were increased significantly during the 3-month titration period (P < 0.0001 for both). In a stepwise Cox regression analysis adjusted for age, sex, glomerular filtration rate, diabetes mellitus, and ischemic HF, baseline and follow-up neurohormone concentrations were predictors of the primary endpoint as follows (baseline hazard ratios): copeptin 1.92, 95% CI 1.233–3.007, P = 0.004; midregional proadrenomedullin 2.79, 95% CI 1.297–5.995, P = 0.009; midregional proatrial natriuretic peptide 2.05, 95% CI 1.136–3.686, P = 0.017; C-terminal endothelin-1 precursor fragment 2.24, 95% CI 1.133–4.425, P = 0.025; B-type natriuretic peptide 1.46, 95% CI 1.039–2.050, P = 0.029. Conclusions: In pharmacologically unstable chronic HF patients, baseline values and follow-up measures of copeptin, midregional proadrenomedullin, C-terminal endothelin-1 precursor fragment, midregional proatrial natriuretic peptide, and B-type natriuretic peptide were equally predictive of all-cause mortality. Relative change of neurohormone values was noncontributory.

Increased Complement Factor H with Decreased Factor B Determined by Proteomic Differential Displays as a Biomarker of Tai Chi Chuan Exercise [Brief Communications]

Background: Exhaustive exercise can be associated with short-term immune suppression, but moderate exercise such as tai chi chuan (TCC) has been shown to have beneficial effects on immunity. The mechanisms for the health benefits of exercise remain to be determined, and no potential biomarkers for these beneficial health effects have been identified. This study investigated serum proteomic markers in individuals participating in TCC exercise. Methods: Two-dimensional fluorescence difference gel electrophoresis was used to compare proteomic markers in 3 individuals before and after 12 weeks of TCC exercise. The different protein spots were identified by mass spectrometry and validated in an additional 20 individuals by western blot analysis. Results: We identified 39 protein spots for 18 proteins with a noticeable increase or decrease after TCC exercise. Validation of the differentially displayed proteins with 20 paired pre- and postexercise samples revealed a significant increase in complement factor H (P = 0.0034) associated with decreases in C1 esterase inhibitor (P = 0.0038) and complement factor B (P = 0.0029). Conclusions: In this first study of proteomic biomarkers of TCC exercise, we found an increase in complement factor H associated with a decrease in complement factor B. Complement factor H is involved in protection from microangiopathy and macular degeneration and may represent a useful marker of the health effects of exercise.

Association of Very Highly Elevated C-Reactive Protein Concentration with Cardiovascular Events and All-Cause Mortality [Brief Communications]

Background: The clinical relevance of very highly increased high-sensitivity C-reactive protein (hsCRP) concentrations (>10 mg/L) is incompletely understood. We examined the association between very highly increased hsCRP and risk of incident cardiovascular disease (CVD) events and all-cause mortality. Methods: We recruited 5248 participants free from overt CVD and acute infection [mean age 53.5 (SD 12.4) years, 55.5% women] from the Scottish Health Survey, a representative sample of community-dwelling adults. hsCRP and other conventional risk factors were measured at baseline. Results: Over an average of 7 years’ follow-up, there were a total of 259 incident CVD events (including myocardial infarction, coronary artery bypass, percutaneous coronary angioplasty, stroke, heart failure) and 357 all-cause deaths. Very highly increased hsCRP was associated with CVD events after adjustment for Framingham risk score (FRS), body mass index (BMI), central obesity, and hormone replacement therapy (HRT) (hazard ratio 2.40, 95% CI 1.51–3.81) and also with all-cause death (hazard ratio 3.64, 95% CI 2.57–5.15). With the addition of CRP scores to the conventional Framingham model, 7.4% of participants were reclassified into a high-risk (>20% FRS) CVD category. Very highly increased hsCRP was also associated with several modifiable risk factors, including smoking, HDL cholesterol, and central obesity. Conclusions: hsCRP >10 mg/L was a stronger predictor of clinical events than a conventional cut point of 3 mg/L. Very highly increased hsCRP may provide clinically meaningful prognostic information.

Detection of Increased Amounts of Cell-Free Fetal DNA with Short PCR Amplicons [Brief Communications]

Aim: A digital PCR approach has recently been suggested to detect greater amounts of cell-free fetal DNA in maternal plasma than conventional real-time quantitative PCR (qPCR). Because the digital qPCR approach uses shorter PCR amplicons than the real-time qPCR assay, we investigated whether a real-time qPCR assay appropriately modified for such short amplicons would improve the detection of cell-free fetal DNA. Method: We developed a novel universal-template (UT) real-time qPCR assay that was specific for the DYS14 sequence on Y chromosome and had a short amplicon size of 50 bp. We examined this "short" assay with 50 maternal plasma samples and compared the results with those for a conventional real-time qPCR assay of the same locus but with a longer amplicon (84 bp). Results: Qualitatively, both assays detected male cell-free fetal DNA with the same specificity and detection capability. Quantitatively, however, the new UT real-time qPCR assay for shorter amplicons detected, on average, almost 1.6-fold more cell-free fetal DNA than the conventional real-time qPCR assay with longer amplicons. Conclusions: The use of short PCR amplicons improves the detection of cell-free fetal DNA. This feature may prove useful in attempts to detect cell-free fetal DNA under conditions in which the amount of template is low, such as in samples obtained early in pregnancy.

Analytical Considerations in the Investigation of Mixed Cryoglobulinemia [Letters to the Editor]

In Reply [Letters to the Editor]

What Criteria Should Be Used to Assess Troponin Assays? [Letters to the Editor]

Call for Nominations [Clinical Chemist]

Lily Robinson and Up in Arms: Recollections [Clinical Chemist]

What Is Your Guess? Unexpected Ethanol in Urine: Increasing Proof [Clinical Chemist]

Unveiling the Right Side: Day Lily [Clinical Chemist]