[Predictive value of CONUT score and dialysis age for peritoneal dialysis-associated peritonitis]

Objective: To explore the predictive value of controlling nutritional status (CONUT) score and dialysis age for peritoneal dialysis-associated peritonitis (PDAP). Methods: This study was a follow-up study. Patients with end-stage renal disease who received peritoneal dialysis (PD) for the first time in the Department of Nephrology, the Third Affiliated Hospital of Suzhou University from January 2010 to December 2020 were enrolled in the study. Patients were divided into non-peritonitis group, mono group (only once PDAP occurred in one year) and frequent group (twice or more PDAP occurred in one year) according to the occurrence and frequency of PDAP during follow-up. The demographic, clinical and laboratory data of patients were collected, and the body mass index and CONUT score were recorded after half a year. Cox regression analysis was used to screen the relevant factors, and receiver operating characteristic (ROC) curve was used to analyze the predictive value of CONUT score and dialysis age for PDAP. Results: A total of 324 PD patients were included, with 188 males (58.0%) and 136 females (42.0%), and aged［M（Q₁，Q₃）］48 (37, 60) years old. The follow-up time was 33 (19, 56) months. PDAP occurred in 112 patients (34.6%), including 63 patients (19.4%) in mono group and 49 patients (15.1%) in frequent group. Multivariate Cox regression analysis showed that half-year CONUT score (HR=1.159, 95%CI: 1.047-1.283, P=0.004) was a risk factor for PDAP, and the baseline CONUT score (HR=1.194, 95%CI: 1.012-1.408, P=0.036) was a risk factor for frequent peritonitis. The area under ROC curve of baseline CONUT score combined with dialysis age in predicting PDAP and frequent peritonitis was 0.682 (95%CI: 0.628-0.733) and 0.676 (95%CI: 0.622-0.727), respectively. Conclusion: CONUT score and dialysis age have certain predictive value for PDAP, and the predictive value of combined diagnosis is higher, which may be used as a potential predictor for PDAP in PD patients.

Longitudinal Study of SARS-CoV-2 Antibody Characteristics Using Label-Free Immunoassays

Introduction/Objective

Since the start of the COVID-19 pandemic, much research has focused on the kinetics and magnitude of humoral immune response. With the advantages of monitoring real-time immunoreactions, label-free immunoassay (LFIA) is becoming a powerful tool in serology studies. We have developed LFIAs to measure SARS- CoV-2 antibody avidity and neutralization activity in a cohort of COVID-19 patients and determine if they correlate with antibody concentration. Serial serum samples collected from mild to severe COVID-19 patients were measured out to 8 months post-symptom onset to determine the durability of the neutralizing antibody response.

Methods/Case Report

Based on thin-film interferometry technology, we established a label-free IgG avidity assay and a label-free surrogate virus neutralization test (LF-sVNT). For measurement, sensing probes pre-coated with receptor-binding domain (RBD) of SARS-CoV-2 spike protein are applied to serum samples containing SARS-CoV-2 antibodies. The label-free IgG avidity assay measures the binding strength between RBD and IgG under urea dissociation. The LF-sVNT analyzes the binding ability of RBD to ACE2 after neutralizing RBD with antibodies.

Results (if a Case Study enter NA)

IgG avidity indices and neutralizing antibody titers (IC50) were determined from serum samples (n=246) from COVID-19 patients (n=113). IgG concentrations were measured using a fluorescent immunoassay. The neutralizing antibody titers showed a weak correlation with IgG concentrations and no correlation with IgG avidity indices. Over the time course up to 8 months post-symptom onset, IgG concentrations and neutralizing antibody titers presented similar trends: an initial rise, plateau and then in some cases a gradual decline after 40 days. The IgG avidity indices, in the same cases, plateaued after the initial rise.

Conclusion

The results demonstrated that LFIA could be used an excellent solution in the determination of SARS- CoV-2 antibody characteristics. The study found that IgG concentration and neutralizing antibody titer declined over time, while IgG avidity index remained constant after reaching a plateau. The decline of antibody neutralization activity can be attributed to the reduction in antibody quantity rather than the deterioration of antibody quality, as measured by antibody avidity.

[Interpretation of group standard for Clostridioides difficile infection diagnosis]

Clostridioides difficile is a key pathogen of antibiotic related diarrhea and hospital associated infection, causing several outbreaks in Europe and North Americans and resulting in severe disease burden. However, the standardized diagnostic principle and detection specifications in C. difficile infection (CDI) survey are limited in China, and the infection rate and disease burden of CDI in China are unclear. Therefore, National Institute for Communicable Disease Control and Prevention,National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, together with another 11 institutions, draft the group standard entitled "Diagnosis of Clostridium difficile infection (T/CPMA 008-2020)" of Chinese Preventive Medicine Association. Based on the principle of "legality, scientificity, advancement, and feasibility", this standard clarifies risk factors, diagnosis principles, diagnoses and differential diagnoses in order to improve the accuracy of CDI diagnosis in clinical practice, guide the surveillance for CDI, and understand the infection rate and disease burden of CDI in China.

Prognostic gene expression signature for high-grade serous ovarian cancer

BACKGROUND

Median overall survival (OS) for women with high-grade serous ovarian cancer (HGSOC) is ∼4 years, yet survival varies widely between patients. There are no well-established, gene expression signatures associated with prognosis. The aim of this study was to develop a robust prognostic signature for OS in patients with HGSOC.

PATIENTS AND METHODS

Expression of 513 genes, selected from a meta-analysis of 1455 tumours and other candidates, was measured using NanoString technology from formalin-fixed paraffin-embedded tumour tissue collected from 3769 women with HGSOC from multiple studies. Elastic net regularization for survival analysis was applied to develop a prognostic model for 5-year OS, trained on 2702 tumours from 15 studies and evaluated on an independent set of 1067 tumours from six studies.

RESULTS

Expression levels of 276 genes were associated with OS (false discovery rate < 0.05) in covariate-adjusted single-gene analyses. The top five genes were TAP1, ZFHX4, CXCL9, FBN1 and PTGER3 (P < 0.001). The best performing prognostic signature included 101 genes enriched in pathways with treatment implications. Each gain of one standard deviation in the gene expression score conferred a greater than twofold increase in risk of death [hazard ratio (HR) 2.35, 95% confidence interval (CI) 2.02-2.71; P < 0.001]. Median survival [HR (95% CI)] by gene expression score quintile was 9.5 (8.3 to -), 5.4 (4.6-7.0), 3.8 (3.3-4.6), 3.2 (2.9-3.7) and 2.3 (2.1-2.6) years.

CONCLUSION

The OTTA-SPOT (Ovarian Tumor Tissue Analysis consortium - Stratified Prognosis of Ovarian Tumours) gene expression signature may improve risk stratification in clinical trials by identifying patients who are least likely to achieve 5-year survival. The identified novel genes associated with the outcome may also yield opportunities for the development of targeted therapeutic approaches.

Low pretreatment PNI correlates with worse survival in patients with stage III/IV NSCLC who received chemotherapy

The aim of this study was to investigate the prognostic value of the prognostic nutritional index (PNI) on the long-term survival of non-small cell lung cancer (NSCLC) patients who received platinum-based chemotherapy. Data on nutritional parameters and clinicopathological characteristics [e.g., albumin, total protein, body mass index (BMI), eastern cooperative oncology group (ECOG) performance status, stage, pathology, treatment strategy] were analyzed and retrospectively correlated with overall survival (OS). The PNI was calculated based on the concentration of albumin and lymphocyte count [10 × albumin, (g/dl) + 0.005 × lymphocyte (count/mm3)]. A receiver operating characteristic curve (ROC) analysis was used to find the optimal cut-off value of PNI. Univariate and multivariate analyses were used to evaluate the prognostic value of PNI. A total of 186 patients met the inclusion criteria. The optimal cut-off value for PNI was 50.45. Compared with the parameters of the low PNI group (n=76), high PNI was significantly associated with adenocarcinoma type, stage III, better ECOG and comprehensive treatment modality. The univariate analysis demonstrated that OS was superior when PNI ≥50.45, albumin ≥35 g/l, platelet-lymphocyte ratio (PLR) ≥163 and ECOG <2, and when the patient received a comprehensive treatment modality. In the multivariate analysis, PNI, TNM stage and treatment strategy were identified as independent predictors of survival in this study. This retrospective study demonstrated that a low PNI was related to worse overall survival in patients with stage III/IV NSCLC who received platinum-based chemotherapy. These data provided a conceptual basis for further research on the clinical application of the PNI index for patients receiving chemotherapy for intermediate- and advanced-stage NSCLC.

Analytical validation of a novel multi-analyte plasma test for lung nodule characterization

BACKGROUND

In the National Lung Screening Trial, 96.4% of nodules had benign etiology. To avoid unnecessary actions and exposure to harm, individuals with benign disease must be identified. We describe herein the analytical validation of a multi-analyte immunoassay for characterizing the risk that a lung nodule found on CT is malignant. Those at lower risk may be considered for serial surveillance to avoid unnecessary and potentially harmful procedures. While those nodules characterized at higher risk may be appropriate for more aggressive actions.

OBJECTIVE

To validate the analytical performance of multiplexed plasma protein assays used in a novel test for lung nodule characterization.

METHODS

A multiplexed immunoassay panel for the measurement of plasma proteins in current smokers who present with a lung nodule on CT scan was evaluated in a clinical testing laboratory. Assay analytical sensitivity, reproducibility, precision, and recovery of Epidermal Growth Factor Receptor (EGFR), Prosurfactant protein B (ProSB), and Tissue Inhibitor of Metalloproteinases 1 (TIMP1) from human EDTA plasma samples were evaluated across multiple runs, lots, and technicians. Interfering substances and sample pre-analytical storage conditions were evaluated for their effect on analyte recovery. The lung nodule risk score reproducibility was assessed across multiple lots.

RESULTS

The assay sensitivities were 0.10 ng/mL EGFR, 0.02 ng/mL ProSB, and 0.29 ng/mL TIMP1 with over three orders of magnitude in the assay dynamic ranges. The assays and analytes are robust to pre-analytical sample handling and the plasma can be stored for up to 4 days at 4°C either when freshy collected or thawed after long-term storage at -80°C. Total imprecision after 20 days of testing remained under 9% for all three assays. Risk score variability remained within a ± 10% risk score range.

CONCLUSIONS

The three protein assays comprising the multi-analyte plasma test for lung nodule characterization performed quite acceptably in a clinical laboratory.

Risk assessment for indeterminate pulmonary nodules using a novel, plasma-protein based biomarker assay

BACKGROUND

The increase in lung cancer screening is intensifying the need for a noninvasive test to characterize the many indeterminate pulmonary nodules (IPN) discovered. Correctly identifying non-cancerous nodules is needed to reduce overdiagnosis and overtreatment. Alternatively, early identification of malignant nodules may represent a potentially curable form of lung cancer.

OBJECTIVE

To develop and validate a plasma-based multiplexed protein assay for classifying IPN by discriminating between those with a lung cancer diagnosis established pathologically and those found to be clinically and radiographically stable for at least one year.

METHODS

Using a novel technology, we developed assays for plasma proteins associated with lung cancer into a panel for characterizing the risk that an IPN found on chest imaging is malignant. The assay panel was evaluated with a cohort of 277 samples, all from current smokers with an IPN 4-30 mm. Subjects were divided into training and test sets to identify a Support Vector Machine (SVM) model for risk classification containing those proteins and clinical factors that added discriminatory information to the Veteran's Affairs (VA) Clinical Factors Model. The algorithm was then evaluated in an independent validation cohort.

RESULTS

Among the 97 validation study subjects, 68 were grouped as having intermediate risk by the VA model of which the SVM model correctly identified 44 (65%) of these intermediate-risk samples as low (n=16) or high risk (n=28). The SVM model negative predictive value (NPV) was 94% and its sensitivity was 94%.

CONCLUSION

The performance of the novel plasma protein biomarker assay supports its use as a noninvasive risk assessment aid for characterizing IPN. The high NPV of the SVM model suggests its application as a rule-out test to increase the confidence of providers to avoid aggressive interventions for their patients for whom the VA model result is an inconclusive, intermediate risk.

Prognostic impact of FOXF1 polymorphisms in gastric cancer patients

A recent genome-wide association study identified seven single-nucleotide polymorphisms (SNPs) in region 16q24, near the Forkhead box-F1 (FOXF1) gene, which confer susceptibility to esophageal adenocarcinoma. We examined whether these SNPs are associated with clinical outcomes in gastric cancer (GC) patients in Japan and the United States. A total of 362 patients were included in this study: 151 Japanese GC patients treated with first-line S1 plus CDDP (training cohort) and 211 GC patients from Los Angeles County (LAC; validation cohort). Genomic DNA was isolated from whole blood or tumor tissue and analyzed by PCR-based direct DNA sequencing. Cox proportional hazard regression analyses were used to assess relationships between FOXF1 SNPs and progression-free survival (PFS) and overall survival (OS). FOXF1 rs3950627 was significantly associated with survival in both the training and validation cohorts. Japanese patients with the C/C genotype had a longer PFS (median 8.2 vs 5.3 months, hazard ratio (HR) 1.44, P=0.037) and OS (median 16.4 vs 12.2 months, HR 1.44, P=0.043) compared to patients with any A allele. Similarly, LAC patients with the C/C genotype had improved OS (3.9 vs 2.3 years, HR 1.5, P=0.022). Subgroup analyses showed these associations were specific to male patients and primary tumor subsite. Our findings suggest that FOXF1 rs3950627 might be a promising prognostic marker in GC patients.

Explaining Disparities in Ovarian Cancer Incidence Rates between Women of African and European Ancestry: The Role of Genetic Factors

Non-Hispanic White (NHW) women are at higher risk of ovarian cancer than African-American (AA) women. Approximately 30% of the difference in age-adjusted invasive epithelial ovarian cancer incidence rates (AAIR) between the two groups can be explained by differing oophorectomy rates and the prevalence of non-genetic risk and protective factors. Our purpose was to determine how much of the remaining difference in AAIRs could be explained by varying allele frequencies between NHWs and AAs for 18 genome-wide significant common susceptibility variants for ovarian cancer. Using data on 13,385 cases and 24,875 controls from the Ovarian Cancer Association Consortium, a genetic risk score (GRS) was created from 18 single nucleotide polymorphisms (SNPs) associated with ovarian cancer risk following the Collaborative Oncological Gene-environment Study (COGS) effort. Relative risks for each GRS quintile were estimated using conditional logistic regression, adjusting for genetic ancestry and conditioning on study site, age, and race. The population attributable risk percent (PAR) for GRS above the lowest quintile was calculated using the Bruzzi method. Previously reported oophorectomy and non-genetic risk factor (talc, oral contraceptive use, family history of ovarian cancer, endometriosis, parity and tubal ligation) adjusted incidence rates for ovarian cancer in NHWs and AA's were 7.2 and 5.8 per 100,000 respectively. These incidence rates were further adjusted for the contribution of the GRS from this analysis. The subsequent genetic PAR adjusted rate was 5.1 per 100,000 for the European ancestry group and 4.9 for the African ancestry group, after taking into account the different oophorectomy rates and prevalence of non-genetic risk factors. These incidence rates show the unexplained difference in incidence rates between NHWs and AAs is only 3.9%. Future efforts should focus on incorporating novel non-genetic and genetic factors into this analysis to determine whether essentially all of the difference in incidence between these groups can be explained.

The effect of leflunomide on the transplanted endometriosis lesions in SD rats

OBJECTIVE

To investigate the effects of the leflunomide (LEF) on the size of the transplanted endometriosis (EMS) lesions and trans- forming growth factor (TGF) -β1gray level in SD rats.

MATERIALS AND METHODS

EMS was surgically induced in rats by autologous trans- plantation and the focal volume was also measured. The rats were divided into three groups: group A: normal SD rats, group B: rats irrigated by one ml-kg⁻¹d⁻¹ saline for three weeks, and group C: rats irrigated by 35 mg-kg⁻¹d⁻¹ LEF for three weeks. The rats were then sacrificed and measured their focal volume and TGF-β1 gray value with immunohistochemical method.

RESULTS

The sizes of the focal volume in group C were significantly reduced compared to the rats before feeding, and the volume in group C was smaller than group B after feeding and so was the TGF-β1.

CONCLUSION

LEF could be a new therapeutic drug for EMS.

Obesity and survival among women with ovarian cancer: results from the Ovarian Cancer Association Consortium

Background:

Observational studies have reported a modest association between obesity and risk of ovarian cancer; however, whether it is also associated with survival and whether this association varies for the different histologic subtypes are not clear. We undertook an international collaborative analysis to assess the association between body mass index (BMI), assessed shortly before diagnosis, progression-free survival (PFS), ovarian cancer-specific survival and overall survival (OS) among women with invasive ovarian cancer.

Methods:

We used original data from 21 studies, which included 12 390 women with ovarian carcinoma. We combined study-specific adjusted hazard ratios (HRs) using random-effects models to estimate pooled HRs (pHR). We further explored associations by histologic subtype.

Results:

Overall, 6715 (54%) deaths occurred during follow-up. A significant OS disadvantage was observed for women who were obese (BMI: 30–34.9, pHR: 1.10 (95% confidence intervals (CIs): 0.99–1.23); BMI: ⩾35, pHR: 1.12 (95% CI: 1.01–1.25)). Results were similar for PFS and ovarian cancer-specific survival. In analyses stratified by histologic subtype, associations were strongest for women with low-grade serous (pHR: 1.12 per 5 kg m⁻²) and endometrioid subtypes (pHR: 1.08 per 5 kg m⁻²), and more modest for the high-grade serous (pHR: 1.04 per 5 kg m⁻²) subtype, but only the association with high-grade serous cancers was significant.

Conclusions:

Higher BMI is associated with adverse survival among the majority of women with ovarian cancer.

FGF receptor genes and breast cancer susceptibility: results from the Breast Cancer Association Consortium

BACKGROUND

Breast cancer is one of the most common malignancies in women. Genome-wide association studies have identified FGFR2 as a breast cancer susceptibility gene. Common variation in other fibroblast growth factor (FGF) receptors might also modify risk. We tested this hypothesis by studying genotyped single-nucleotide polymorphisms (SNPs) and imputed SNPs in FGFR1, FGFR3, FGFR4 and FGFRL1 in the Breast Cancer Association Consortium.

METHODS

Data were combined from 49 studies, including 53 835 cases and 50 156 controls, of which 89 050 (46 450 cases and 42 600 controls) were of European ancestry, 12 893 (6269 cases and 6624 controls) of Asian and 2048 (1116 cases and 932 controls) of African ancestry. Associations with risk of breast cancer, overall and by disease sub-type, were assessed using unconditional logistic regression.

RESULTS

Little evidence of association with breast cancer risk was observed for SNPs in the FGF receptor genes. The strongest evidence in European women was for rs743682 in FGFR3; the estimated per-allele odds ratio was 1.05 (95% confidence interval=1.02-1.09, P=0.0020), which is substantially lower than that observed for SNPs in FGFR2.

CONCLUSION

Our results suggest that common variants in the other FGF receptors are not associated with risk of breast cancer to the degree observed for FGFR2.

Genetic variants associated with warfarin dose in African-American individuals: a genome-wide association study

BACKGROUND

VKORC1 and CYP2C9 are important contributors to warfarin dose variability, but explain less variability for individuals of African descent than for those of European or Asian descent. We aimed to identify additional variants contributing to warfarin dose requirements in African Americans.

METHODS

We did a genome-wide association study of discovery and replication cohorts. Samples from African-American adults (aged ≥18 years) who were taking a stable maintenance dose of warfarin were obtained at International Warfarin Pharmacogenetics Consortium (IWPC) sites and the University of Alabama at Birmingham (Birmingham, AL, USA). Patients enrolled at IWPC sites but who were not used for discovery made up the independent replication cohort. All participants were genotyped. We did a stepwise conditional analysis, conditioning first for VKORC1 -1639G→A, followed by the composite genotype of CYP2C9*2 and CYP2C9*3. We prespecified a genome-wide significance threshold of p<5×10(-8) in the discovery cohort and p<0·0038 in the replication cohort.

FINDINGS

The discovery cohort contained 533 participants and the replication cohort 432 participants. After the prespecified conditioning in the discovery cohort, we identified an association between a novel single nucleotide polymorphism in the CYP2C cluster on chromosome 10 (rs12777823) and warfarin dose requirement that reached genome-wide significance (p=1·51×10(-8)). This association was confirmed in the replication cohort (p=5·04×10(-5)); analysis of the two cohorts together produced a p value of 4·5×10(-12). Individuals heterozygous for the rs12777823 A allele need a dose reduction of 6·92 mg/week and those homozygous 9·34 mg/week. Regression analysis showed that the inclusion of rs12777823 significantly improves warfarin dose variability explained by the IWPC dosing algorithm (21% relative improvement).

INTERPRETATION

A novel CYP2C single nucleotide polymorphism exerts a clinically relevant effect on warfarin dose in African Americans, independent of CYP2C9*2 and CYP2C9*3. Incorporation of this variant into pharmacogenetic dosing algorithms could improve warfarin dose prediction in this population.

FUNDING

National Institutes of Health, American Heart Association, Howard Hughes Medical Institute, Wisconsin Network for Health Research, and the Wellcome Trust.

Passive smoking and risk of oesophageal and gastric adenocarcinomas

Few studies have examined the association between passive smoking and the risk of oesophageal and gastric adenocarcinomas. In a population-based case-control study with 2474 participants in Los Angeles County, there was no evidence that passive smoking had any appreciable effect on oesophageal or gastric adenocarcinomas.

Tagging single-nucleotide polymorphisms in candidate oncogenes and susceptibility to ovarian cancer

Low-moderate risk alleles that are relatively common in the population may explain a significant proportion of the excess familial risk of ovarian cancer (OC) not attributed to highly penetrant genes. In this study, we evaluated the risks of OC associated with common germline variants in five oncogenes (BRAF, ERBB2, KRAS, NMI and PIK3CA) known to be involved in OC development. Thirty-four tagging SNPs in these genes were genotyped in approximately 1800 invasive OC cases and 3000 controls from population-based studies in Denmark, the United Kingdom and the United States. We found no evidence of disease association for SNPs in BRAF, KRAS, ERBB2 and PIK3CA when OC was considered as a single disease phenotype; but after stratification by histological subtype, we found borderline evidence of association for SNPs in KRAS and BRAF with mucinous OC and in ERBB2 and PIK3CA with endometrioid OC. For NMI, we identified a SNP (rs11683487) that was associated with a decreased risk of OC (unadjusted P(dominant)=0.004). We then genotyped rs11683487 in another 1097 cases and 1792 controls from an additional three case-control studies from the United States. The combined odds ratio was 0.89 (95% confidence interval (CI): 0.80-0.99) and remained statistically significant (P(dominant)=0.032). We also identified two haplotypes in ERBB2 associated with an increased OC risk (P(global)=0.034) and a haplotype in BRAF that had a protective effect (P(global)=0.005). In conclusion, these data provide borderline evidence of association for common allelic variation in the NMI with risk of epithelial OC.

Sudden death in dilated cardiomyopathy

The purpose of this review is to examine the potential contribution of arrhythmia to the occurrence of sudden death in dilated cardiomyopathy (DCM) and to discuss current treatment options. We performed a search of the MEDLINE database from 1985 to the present and the reference citations of selected articles pertaining to the prognostic significance, management, and pathophysiology of arrhythmias in DCM. A large proportion of patients with DCM die suddenly, most secondary to ventricular arrhythmia and a smaller proportion due to bradyarrhythmia. The presence and severity of ventricular ectopy may predict risk for sudden death, but the role of electrophysiologic study and signal-averaged electrocardiography in further risk stratifying patients remains uncertain. Abnormalities of the autonomic nervous system and renin-angiotensin-aldosterone axis appear to promote the occurrence of ventricular arrhythmias. Angiotensin-converting enzyme inhibitors improve overall mortality in congestive heart failure, and the use of direct angiotensin-receptor antagonists is currently being studied. In addition, beta-receptor antagonists appear to improve morbidity and may prove to improve mortality in heart failure as well. Other interventions still under investigation include amiodarone and the implantable cardioverter-defibrillator. The underlying pathophysiology of sudden death in DCM involves primarily ventricular tachyarrhythmia. Angiotensin-converting enzyme inhibitors remain a mainstay of improving overall mortality, while further study on the roles for newer drugs and devices is ongoing.

Comparative analysis of cardiac troponin I and creatine kinase-MB as markers of acute myocardial infarction

BACKGROUND

The World Health Organization (WHO) criteria for the diagnosis of acute myocardial infarction (AMI) includes presentation of chest pain over 20 min, evolutionary changes on the electrocardiogram (ECG), and abnormal levels of cardiac enzymes.

HYPOTHESIS

A multicenter study was conducted to evaluate the efficacy of cardiac troponin I (cTnI) in detecting and ruling out AMI.

METHODS

The normal range for cTnI in 149 apparently healthy subjects without known history of cardiac or other diseases was 0 to 0.5 ng/ml. Cutoffs of 2.5 ng/ml for c TnI and 5.0 ng/ml for creatine kinase-MB (CK-MB) were used.

RESULTS

The diagnostic sensitivity of blood collected from 291 consecutive patients with suspicion of AMI was 95.0 and 96.4%, respectively, for samples obtained at 4-48 h after AMI onset. CK-MB was more sensitive during the early 4-8 h interval (84 vs. 74%); both had 100% sensitivity from 12-36 h. CTnI remained at 100% for 72 h, while CK-MB declined to 57%. The clinical specificity was 97.4 vs. 85.8%, respectively, on non-AMI patients with cardiac and noncardiac diseases, and those with renal disease.

CONCLUSION

cTnI is an excellent marker for detecting and ruling out AMI, because it has better specificity and a wider diagnostic window than the accepted standard, CK-MB.

Validating genetic risk associations for ovarian cancer through the international Ovarian Cancer Association Consortium

The search for genetic variants associated with ovarian cancer risk has focused on pathways including sex steroid hormones, DNA repair, and cell cycle control. The Ovarian Cancer Association Consortium (OCAC) identified 10 single-nucleotide polymorphisms (SNPs) in genes in these pathways, which had been genotyped by Consortium members and a pooled analysis of these data was conducted. Three of the 10 SNPs showed evidence of an association with ovarian cancer at P< or =0.10 in a log-additive model: rs2740574 in CYP3A4 (P=0.011), rs1805386 in LIG4 (P=0.007), and rs3218536 in XRCC2 (P=0.095). Additional genotyping in other OCAC studies was undertaken and only the variant in CYP3A4, rs2740574, continued to show an association in the replication data among homozygous carriers: OR(homozygous(hom))=2.50 (95% CI 0.54-11.57, P=0.24) with 1406 cases and 2827 controls. Overall, in the combined data the odds ratio was 2.81 among carriers of two copies of the minor allele (95% CI 1.20-6.56, P=0.017, p(het) across studies=0.42) with 1969 cases and 3491 controls. There was no association among heterozygous carriers. CYP3A4 encodes a key enzyme in oestrogen metabolism and our finding between rs2740574 and risk of ovarian cancer suggests that this pathway may be involved in ovarian carcinogenesis. Additional follow-up is warranted.

Dosing algorithm for warfarin using CYP2C9 and VKORC1 genotyping from a multi-ethnic population: comparison with other equations

Objectives: Polymorphism in the genes for cytochrome (CYP)2C9 and the vitamin K epoxide reductase complex subunit 1 (VKORC1) affect the pharmacokinetics and pharmacodynamics of warfarin. We developed and validated a warfarin-dosing algorithm for a multi-ethnic population that predicts the best dose for stable anticoagulation, and compared its performance against other regression equations. Methods: We determined the allele and haplotype frequencies of genes for CYP2C9 and VKORC1 on 167 Caucasian, African–American, Asian and Hispanic patients on warfarin. On a subset where complete data were available (n = 92), we developed a dosing equation that predicts the actual dose needed to maintain target anticoagulation using demographic variables and genotypes. This regression was validated against an independent group of subjects. We also applied our data to five other published warfarin-dosing equations. Results: The allele frequency for CYP2C9*2 and *3 and the A allele for VKORC1 3673 was similar to previously published reports. For Caucasians and Asians, VKORC1 SNPs were in Hardy–Weinberg linkage equilibrium. Some VKORC1 SNPs among the African–American population and one SNP among Hispanics were not in equilibrium. The linear regression of predicted versus actual warfarin dose produced r-values of 0.71 for the training set and 0.67 for the validation set. The regression coefficient improved (to r = 0.78 and 0.75, respectively) when rare genotypes were eliminated or when the 7566 VKORC1 genotype was added to the model. All of the regression models tested produced a similar degree of correlation. The exclusion of rare genotypes that are more associated with certain ethnicities improved the model. Conclusion: Minor improvements in algorithms can be observed with the inclusion of ethnicity and more CYP2C9 and VKORC1 SNPs as variables. Major improvements will likely require the identification of new gene associations with warfarin dosing.

Progesterone receptor variation and risk of ovarian cancer is limited to the invasive endometrioid subtype: results from the Ovarian Cancer Association Consortium pooled analysis

There is evidence that progesterone plays a role in the aetiology of invasive epithelial ovarian cancer. Therefore, genes involved in pathways that regulate progesterone may be candidates for susceptibility to this disease. Previous studies have suggested that genetic variants in the progesterone receptor gene (PGR) may be associated with ovarian cancer risk, although results have been inconsistent. We have established an international consortium to pool resources and data from many ovarian cancer case–control studies in an effort to identify variants that influence risk. In this study, three PGR single nucleotide polymorphisms (SNPs), for which previous data have suggested they affect ovarian cancer risk, were examined. These were +331 C/T (rs10895068), PROGINS (rs1042838), and a 3′ variant (rs608995). A total of 4788 ovarian cancer cases and 7614 controls from 12 case–control studies were included in this analysis. Unconditional logistic regression was used to model the association between each SNP and ovarian cancer risk and two-sided P-values are reported. Overall, risk of ovarian cancer was not associated with any of the three variants studied. However, in histopathological subtype analyses, we found a statistically significant association between risk of endometrioid ovarian cancer and the PROGINS allele (n=651, OR=1.17, 95% CI=1.01–1.36, P=0.036). We also observed borderline evidence of an association between risk of endometrioid ovarian cancer and the +331C/T variant (n=725 cases; OR=0.80, 95% CI 0.62–1.04, P=0.100). These data suggest that while these three variants in the PGR are not associated with ovarian cancer overall, the PROGINS variant may play a modest role in risk of endometrioid ovarian cancer.

Early detection of acute coronary syndromes and risk stratification by multimarker analysis

Cardiac troponin is the standard biomarker for the diagnosis of acute myocardial infarction (AMI) and risk stratification for short-term adverse cardiac events (death, AMI or need for revascularization). Unfortunately, the concentration of troponin in blood is normal in AMI patients who present early after the onset of symptoms. As such, there is active research being conducted in finding early markers of AMI and risk stratification. Despite years of testing dozens of candidates, no single test has had the necessary clinical sensitivity and specificity for this indication. Therefore, many researchers have advocated multimarker testing. There are two approaches that have been taken for discovering new markers. The proteomic approach involves focusing on the differences in the biochemical signatures between the tissues or biological fluids of normal compared with diseased individuals. Specific biochemical targets are not preselected. The pathophysiologic approach involves combining biomarkers that indicate a particular pathway or event known to be involved in the disease process. In both approaches, some bioinformatic algorithm will be necessary in order to combine the information provided by the individual tests. Representative approaches include the Multimarker Index™, classification and regression tree analysis and neural networks.

High carrier prevalence of deficient and null alleles of CYP2 genes in a major USA hospital: implications for personalized drug safety

Many drugs are metabolized by highly polymorphic cytochrome P450 (CYP) enzymes. Among these enzymes, members of the CYP2 family coded by the CYP2D6, CYP2C9 and CYP2C19 genes are best amenable to the precise prediction of an individual's innate capacity to metabolize drugs by DNA typing of inherited null and deficient alleles. We determined the frequency of these alleles and the prevalence of their carriers in a New England, USA, tertiary care center to assess underlying population genetic features for the practice of personalized medicine. We determined that 54, 25 and 27% are carriers of at least one deficient or null allele for the CYP2D6, CYP2C9 and CYP2C19 genes, respectively. Furthermore, 6% of individuals are carriers of two null alleles for CYP2D6 and are predicted to have no biochemical activity for this isoenzyme. These results support the implementation of DNA typing of CYP2 genes to diagnose adverse drug reactions and to prevent a substantial number of patients being prescribed drugs they cannot adequately metabolize.

Analysis of the Albumin Cobalt Binding (ACB) test as an adjunct to cardiac troponin I for the early detection of acute myocardial infarction

Human albumin has the ability to bind cobalt at the N-terminus. The exposure of circulating albumin to ischemic tissue alters the ability of albumin to bind cobalt, probably through a mechanism involving free-radical production. The Albumin Cobalt Binding (ACB) test measures the alteration in albumin metal binding, and elevation of the ACB test is thought to be an early indicator of myocardial ischemia. In a previous multicenter study of chest pain patients presenting to the emergency department (ED), this test demonstrated high negative predictive value and sensitivity in the sample collected at presentation for predicting cardiac troponin I (cTnI)-negative or cTnI-positive results 6-24 h later. Since the completion of that report, the European Society of Cardiology (ESC) and the American College of Cardiology (ACC) have redefined the criteria for the diagnosis of acute myocardial infarction (AMI). The data from the multicenter ACB study were re-examined using the new diagnostic criteria for AMI to determine if combining the ACB test with troponin improved the sensitivity of either assay used alone for early diagnosis of AMI. Assay values were compared to either the final discharge diagnosis made at each site or to a diagnosis of AMI using the strict application of the ESC/ACC guidelines. Using the criterion of physician's discharge diagnosis and using blood collected at ED presentation, the cTnI test alone had a sensitivity of 23.9%, and the ACB test alone had a sensitivity of 39.1%, but the sensitivity significantly increased to 55.9% (p < 0.001 over cTnI alone) when both tests were used in combination. The sensitivity of the combination of ACB and cTnI tests at the 1- to 6-h time-point was 86.7% and at the >6- to 12-h time-point was 93.5%, but they were not significantly improved over the cTnI test alone. In conclusion, using the new ESC/ACC criteria, the combination also resulted in a statistically significant higher diagnostic sensitivity on blood collected at presentation. These data indicate a possible role of the ACB test in the early triage of patients with chest pain.

Does place of birth influence endogenous hormone levels in Asian-American women?

In 1983-87, we conducted a population-based case-control study of breast cancer in Asian women living in California and Hawaii, in which migration history (a composite of the subject's place of birth, usual residence in Asia (urban/rural), length of time living in the West, and grandparents' place of birth) was associated with a six-fold risk gradient that paralleled the historical differences in incidence rates between the US and Asian countries. This provided the opportunity to determine whether endogenous hormones vary with migration history in Asian-American women. Plasma obtained from 316 premenopausal and 177 naturally premenopausal study controls was measured for levels of estrone (E1), estradiol (E2), estrone sulphate (E1S), androstenedione (A), testosterone (T), dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulphate (DHEAS), progesterone (PROG) and sex hormone-binding globulin (SHBG). Levels of the oestrogens and sex hormone-binding globulin did not differ significantly between Asian- and Western-born women, although among premenopausal women, those least westernised had the lowest levels of E1, E2, and E1S. Androgen levels, particularly DHEA, were lower in women born in the West. Among premenopausal women, age-adjusted geometric mean levels of DHEA were 16.5 and 13.8 nmol l(-1) in Asian- and Western-born women respectively; in postmenopausal women these values were 11.8 and 9.2 nmol l(-1), (P<0.001) respectively. Among postmenopausal women, androgens tended to be highest among the least westernised women and declined as the degree of westernisation increased. Our findings suggest that aspects of hormone metabolism play a role in population differences in breast cancer incidence.

Multicenter Evaluation of an Automated Assay for Troponin I

Background: Cardiac troponin I (cTnI) is a powerful tool to aid in the diagnosis of myocardial infarction and cardiac muscle damage. We describe an assay that overcomes problems of early assays that were often affected by cTnI degradation, assay interference, poor sensitivity, and imprecision.

Methods: The analytical performance of the Access® AccuTnITM assay (Beckman Coulter) was evaluated at five institutions. Controls, zero calibrator, and diluted patient samples were used to determine precision, detection limit, functional sensitivity, and linearity. The 97.5 and 99 percentiles of a reference population were determined. Common interferents and heterophilic patient samples were tested. Equimolarity was determined by assaying samples with various ratios of free and complexed cTnI. Matched samples drawn into serum, EDTA, lithium heparin, and sodium heparin sample tubes were compared.

Results: Total imprecision (CVs) was 4.0–8.8% between 0.40 and 31 μg/L cTnI. The detection limit was &lt;0.01 μg/L. The 97.5 percentile upper reference limit (URL) was 0.03 μg/L (CV = 20%), and the 99 percentile URL was 0.04 μg/L (CV = 14%). Total CVs of 10% and 20% were seen at and above 0.06 and 0.03 μg/L, respectively. The assay was linear to &gt;60 μg/L and not affected by common assay interferents. An equimolar response was observed with free, complexed, phosphorylated, and dephosphorylated forms of cTnI. Results were 4% lower in serum and 14% lower in EDTA plasma than in lithium heparin plasma (P &lt;0.01), independent of cTnI concentration.

Conclusion: AccuTnI is a sensitive and precise assay for the measurement of cTnI.

Dietary heterocyclic amines and microsatellite instability in colon adenocarcinomas

Microsatellite instability (MSI) is now an accepted and important pathway in colon tumorigenesis, occurring in 10-15% of sporadic colon cancers and almost all hereditary nonpolyposis colon cancers. Little is known about possible environmental influences on MSI status in colon cancer. We conducted an epidemiological study of 276 colon cancer cases in Los Angeles County that was designed to determine the population prevalence of MSI(+) colon cancer and to identify environmental influences in the development of MSI(+) tumors. Our results support the cigarette smoking and MSI(+) association recently reported [Slattery,M.L., Curtin,K., Anderson,K. et al. (2000) J. Natl Cancer Inst., 92, 1831-1836]. Risk of MSI(+) colon cancers increased with increasing dose (number of cigarettes per day) and increasing duration (years of smoking) of smoking. Compared with never-smokers, those who smoked 1-20 pack-years and >20 pack-years showed odds ratios of 1.39 and 1.64, respectively (P for trend = 0.03). In addition, our results show, for the first time, that after adjustment for cigarette smoking habits and red meat intake, patients with MSI(+) colon cancers had significantly higher dietary exposure to heterocyclic aromatic amines (HAA) as determined by two surrogates of high dietary HAA exposure: preference for well-done red meat and high frequencies of certain cooking practices (frying, barbecuing, broiling and using meat drippings). The risk of MSI(+) colon cancer was increased 3-fold (smoking/red meat intake adjusted OR = 3.03, 95% CI = 1.06, 8.63) among patients who preferred to eat red meat that was very well-done and was increased >2-fold (smoking/red meat adjusted OR = 2.33, 95% CI = 1.00, 5.25) among those who frequently fried/barbecued/broiled their meats or used meat drippings. The risk of MSI(+) colon cancer associated with cigarette smoking remained statistically significant after adjustment for high dietary HAA exposure. The significant association between cigarette smoking and dietary HAA with a specific subset of colon cancers may explain, at least in part, inconsistencies in results linking these two exposures to colon cancers. These results provide a potential mechanism of linking HAA exposure and cigarette smoking to a specific subset of colon cancers.

A multiethnic population-based study of smoking, alcohol and body size and risk of adenocarcinomas of the stomach and esophagus (United States)

OBJECTIVES

Since the 1970s incidence rates for esophageal and gastric cardia adenocarcinomas have risen substantially, particularly among white males in the United States. Reasons for the increase of these tumor types are not well understood. We sought to determine the role of smoking, alcohol use, and body size characteristics in the etiology of esophageal, gastric cardia, and distal gastric adenocarcinomas.

MATERIALS AND METHODS

A population-based case-control study that included Whites, African-Americans, Latinos and Asian-Americans diagnosed with incident esophageal (n = 222), gastric cardia (n = 277), and distal gastric adenocarcinomas (n = 443), and 1356 control subjects was conducted in Los Angeles County. Unconditional logistic regression was used to calculate odds ratios (ORs), as an estimate of the relative risk, and corresponding 95% confidence intervals (CIs) for the three tumor types of interest.

RESULTS

After adjustment for age, gender, race, birthplace, and education, current cigarette smoking was a significant risk factor for all tumor types; the association was strongest for esophageal adenocarcinomas (OR = 2.80, 95% CI = 1.8-4.3), intermediate for gastric cardia adenocarcinomas (OR = 2.12, 95% CI = 1.5-3.1), and weaker for distal gastric adenocarcinomas (OR= 1.50, 95% CI = 1.1-2.1). For esophageal adenocarcinomas only, cigarette smoking had a long-lasting deleterious effect, even 20 years after smoking cessation. Alcohol use was not associated with an increased risk of these tumor types. Risks of esophageal and gastric cardia adenocarcinomas also increased statistically significantly in a dose-dependent manner with increasing body mass index measured at ages 20 and 40 years and recently. The positive associations with smoking and body mass index were generally consistent when evaluated separately for Whites, non-Whites, males, and females.

CONCLUSIONS

Cigarette smoking and high body mass index are significant, independent risk factors for esophageal and gastric cardia adenocarcinomas. Studies designed to understand the mechanisms whereby smoking and high body mass influence these tumor types are needed.

B-type natriuretic peptide and its clinical utility in patients with heart failure

The implementation of entirely new clinical laboratory tests such as BNP assays is much more difficult today than it ever has been in the past. Medicare and Medicaid have been operating for many years on fixed reimbursements based on Diagnosis Related Groups (DRGs). Many third-party payers now have capitated contracts, i.e., a fixed reimbursement per member per month, regardless of the number of tests ordered and performed. Laboratories are now cost centers and not sources of revenue, thus the limited amount of income from fee-for-service reimbursements may not sufficient to cover the expenses for performing all testing. Therefore, in order to justify BNP testing, laboratory directors and hospital administrators must be able to demonstrate that implementation of BNP testing results in a savings for the hospital as a whole, even if the laboratory has a negative cost balance. If BNP testing can lead to a reduction or elimination of other tests, or if it improves the efficiency and accuracy of CHF diagnosis so that the number of inappropriate admissions is reduced, the test may be justified. Table 2 lists some specific areas where BNP might impact the other clinical areas. Outcome studies should be performed to determine if any of these changes in clinical practices can be justified.

Effect of dl-praeruptorin A on ATP sensitive potassium channels in human cortical neurons

AIM

To investigate the effect of dl-praeruptorin A (Pd-Ia) on ATP sensitive potassium channels (KATP channel) in human cortical neurons.

METHODS

Using standard whole cell recording method. Cell membranes were held at -40 mV, commanding potential was -30 to +100 mV and duration was 600 ms.

RESULTS

Pd-Ia activated KATP channels in human cortical neurons in a concentration-dependent manner. After consecutive perfusion with external solution containing Pd-Ia 0.001, 0.01, 0.1, and 1 micromol/L, currents increased from control (0.9 +/- 0.4) nA to (1.0 +/- 0.4) nA, (1.1 +/- 0.4) nA, (1.2 +/- 0.4) nA, and (1.3 +/- 0.4) nA (P < 0.05 or P < 0.01, n = 5) respectively. Then the current decreased to (0.90 +/- 0.37) nA (P < 0.01, n = 5) after washout with glibenclamide (10 micromol/L). The increscent part of the currents could nearly be inhibited by specific KATP channel inhibitor.

CONCLUSION

Pd-Ia could open KATP channel and it is a kind of potassium channel opener

Mismatch repair deficiency and CpG island hypermethylation in sporadic colon adenocarcinomas

Many studies have documented CpG island hypermethylation in human colon adenocarcinomas. Several of these reports have additionally found such CpG island hypermethylation to be more extensive in tumors with a mismatch-repair deficiency, as revealed by microsatellite instability (MSI+). Because the source of samples used in these prior studies may not have been representative of the general population, we have reinvestigated this issue using samples from a population-based study. A total of 15 MSI+ tumors were identified, and they were compared with 47 MSI- tumors that were similar in distribution by age, sex, and race. Microdissected tumor and normal adjacent mucosal DNA samples from each patient were subjected to a quantitative DNA methylation analysis at 13 separate CpG dinucleotides located in five CpG islands in four different genes [APC, ESR1 (ER), CDKN2A (p16; promoter and exon 2), and MLH1]. Four of five CpG islands showed a statistically significantly increased level of methylation in tumor tissue compared with adjacent normal mucosa. In contrast to previous studies, we did not find any statistically significant correlations between MSI status and methylation levels of any of the CpG islands other than MLH1. Furthermore, we observed a positive correlation between MLH1 methylation and CDKN2A methylation (P = 0.03), whereas no association was noted between MSI positivity and CDKN2A methylation (P = 0.95). The latter results suggest a possible defect in the protection against CpG island hypermethylation shared between CDKN2A and MLH1 and do not support the notion of a functional association between CDKN2A methylation and the phenotype of mismatch repair deficiency.

Correlation of polymorphisms to coagulation and biochemical risk factors for cardiovascular diseases

Currently, the established risk factors for cardiovascular disease (CVD) are largely environmental in nature. Conflicting studies have suggested that mutations in specific coagulation genes may also provide a genetic basis for CVD risk. We reviewed clinical studies that examined the role of single nucleotide polymorphisms in coagulation and platelet factors, and a biochemical factor to determine if specific genotypes are correlated with patients with a history of arterial thrombotic diseases (acute coronary syndromes or stroke). A meta-analysis was performed on studies for factors II (G20210A variant), V Leiden (G1691A), VII (R353Q), glycoprotein (GP) IIIa receptor (PI(A1/A2)), and methylenetetrahydrofolate reductase (MTHFR, C677T). There was no correlation for factor II or factor V polymorphisms to coronary artery disease (CAD) in 5,607 and 5,431 patients studied, respectively. There was also no correlation for factor II variants and stroke in 3,451 patients studied. For factor V, statistical significance was achieved for the G1691A variant on 3,399 patients with stroke (odds ratio [OR] 1.43, 95% confidence intervals [CI] 1.03 to 1.97). The GP IIIa PI(A1/A2) genotype was associated with increased risk for CAD in 7,920 patients (OR 1.12, 95% CI 1.01 to 1.24), but not for 1,855 patients who had a stroke (OR 0.80, 95% CI 0.62 to 1.04). The combined RQ and RR genotypes of factor VII R353Q were correlated to a reduced risk for CVD in 2,574 patients (OR 0.78, 95% CI 0.65 to 0.93), whereas the QQ genotype had offered more protection (OR 0.53, 95% CI 0.27 to 1.03). The TT homozygous variant of MTHFR was associated with CAD risk in 5,644 patients studied (OR 1.30, 95% CI 1.11 to 1.52) but not for 3,075 patients with stroke. This study shows that for some genes, further studies are unnecessary, whereas for others, no more enrollments are needed. The impact of certain genotypes must be examined in relation to other established risk factors and potentially new therapeutic strategies.

Lifestyle determinants of 5alpha-reductase metabolites in older African-American, white, and Asian-American men

Men with higher endogenous 5alpha-reductase activity may have higher prostate cancer risk. This hypothesis raises two questions: (a) Could racial differences in 5alpha-reductase activity explain the observed racial differences in prostate cancer risk? and (b) Could a man reduce his activity level by modifying his lifestyle? To address these questions, we measured two hormonal indices of 5alpha-reductase activity [serum levels of androstane-3alpha-17beta-diol glucuronide (3alpha-diol G) and androsterone glucuronide (AG)] in healthy, older African-American, white, and Asian-American men, who are at high, intermediate, and low prostate cancer risk, respectively. We also examined associations between these metabolite levels and such lifestyle characteristics as body size and physical activity as well as select aspects of medical history and family history of prostate cancer. Men included in this cross-sectional analysis (n = 1054) had served as control subjects in a population-based case-control study of prostate cancer we conducted in California, Hawaii, and Vancouver, Canada and provided information on certain personal attributes and donated blood between March 1990 and March 1992. In this study, concentrations of 3alpha-diol G declined significantly with age and increased significantly with body mass index. Mean levels of 3alpha-diol G, adjusted for age and body mass index, were 6.1 ng/ml in African-Americans, 6.9 ng/ml in whites and 4.8 ng/ml in Asian-Americans. These differences were statistically significant (African-Americans versus whites: P < 0.01; whites versus Asian-Americans: P < 0.001). Concentrations of AG decreased significantly with age, but only in whites, and were unrelated to any of the reported personal attributes. Mean levels of AG, adjusted for age, were 44.1 ng/ml in African-Americans, 44.9 ng/ml in whites, and 37.5 ng/ml in Asian-Americans (Asian-Americans versus whites, P < 0.001). In conclusion, older African-American and white men have similar levels of these two indices of 5alpha-reductase activity, and these levels are higher than those of older Asian-American men. This difference may be related to the lower prostate cancer risk in Asian-Americans.

Standardization of cardiac troponin I assays: round Robin of ten candidate reference materials

BACKGROUND

Cardiac troponin I (cTnI) results vary 100-fold among assays. As a step toward standardization, we examined the performance of 10 candidate reference materials (cRMs) in dilution studies with 13 cTnI measurement systems.

METHODS

Solutions of 10 cTnI cRMs, each characterized by NIST, were shipped to the manufacturers of 13 cTnI measurement systems. Manufacturers used their respective diluents to prepare each cRM in cTnI concentrations of 1, 10, 25, and 50 microg/L. For the purpose of ranking the cRMs, the deviation of each cTnI measurement from the expected response was assessed after normalization with the 10 microg/L cTnI solution. Normalized deviations were examined in five formats. Parameters from linear regression analysis of the measured cTnI vs expected values were also used to rank performance of the cRMs.

RESULTS

The three cRMs demonstrating the best overall rankings were complexes of troponins C, I, and T. The matrices for these three cRMs values differed; one was reconstituted directly from the lyophilized form submitted by the supplier; one was submitted in liquid form, lyophilized at NIST, and subsequently reconstituted; and the third was evaluated in the liquid form received from the supplier. The cRM demonstrating the fourth best performance was a binary complex of troponins C and I supplied in lyophilized form and reconstituted before distribution.

CONCLUSIONS

The cRMs demonstrating the best performance characteristics in 13 cTnI analytical systems will be included in subsequent activities of the cTnI Standardization Committee of the AACC.