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.

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.

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.

The use of lamellar body counts to predict fetal lung maturity in pregnancies complicated by diabetes mellitus

OBJECTIVE

The purpose of this study was (1) to correlate amniotic fluid lamellar body counts with the lecithin/sphingomyelin ratio and the presence of phosphatidylglycerol in pregnancies that were complicated by maternal diabetes mellitus and (2) to determine a lamellar body count value that maximizes sensitivity and specificity in the prediction of fetal lung maturity.

STUDY DESIGN

We reviewed our prospectively collected perinatal database from November 1992 through October 1999 to identify pregnancies that were complicated by diabetes mellitus for which fetal lung maturity studies had been performed within 72 hours of delivery. Lamellar body counts were correlated with lecithin-sphingomyelin ratio and phosphatidylglycerol values. The sensitivities and specificities of various lamellar body count cutoff values were calculated with the lecithin/sphingomyelin ratio and phosphatidylglycerol values as indicators of fetal lung maturity. Receiver operating curves were used to determine the lamellar body count that indicated fetal lung maturity. Our neonatal database was reviewed for this same time period to obtain all cases of respiratory distress syndrome. The maternal data were compared with the neonatal data to determine whether distress syndrome had developed in an infant who had undergone fetal lung maturity testing respiratory.

RESULTS

Lamellar body counts were correlated with lecithin/sphingomyelin ratio (r = 0.51, P <.001) and phosphatidylglycerol values (r = 0.57, P <.001) in 90 diabetic pregnant patients. A lamellar body count of 37,000/microL was found to have a sensitivity of 80% and a specificity of 100% in the prediction of fetal lung maturity by standardized methods of phospholipid analysis. There were no cases of neonatal respiratory distress syndrome in this study population.

CONCLUSION

The lamellar body count is a valid, rapid screening test for the determination of biochemical fetal lung maturity in pregnancies that are complicated by diabetes mellitus. A lamellar body count of > or =37,000/microL correlated with the lecithin/sphingomyelin ratio and phosphatidylglycerol values in the pregnancies of diabetic patients. Use of lamellar body counts in pregnancies that are complicated by diabetes mellitus could decrease the need for time-consuming and more costly phospholipid profiles. A full phospholipid profile is recommended for amniotic fluid specimens with lamellar body count values of <37,000/microL.

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.

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.

Characteristics of an Albumin Cobalt Binding Test for assessment of acute coronary syndrome patients: a multicenter study

BACKGROUND

The ability of the N-terminal region of human albumin to bind cobalt is diminished by myocardial ischemia. The characteristics of an assay based on albumin cobalt binding were assessed in suspected acute coronary syndrome patients and in a control reference population. The ability of the Albumin Cobalt Binding (ACB) Test measurement at presentation to predict troponin-positive or -negative results 6-24 h later was also examined.

METHODS

We enrolled 256 acute coronary syndrome patients at four medical centers. Blood specimens were collected at presentation and then 6-24 h later. The dichotomous decision limit and performance characteristics of the ACB Test for predicting troponin-positive or -negative status 6 h-24 h later were determined using ROC curve analysis. Results for 32 patients could not be used because the time of onset of ischemia appeared to have been >3 h before presentation or was uncertain. The reference interval was determined by parametric analysis to estimate the upper 95th percentile of a reference population (n = 109) of ostensibly healthy individuals.

RESULTS

Increased cTnI was found in 35 of 224 patients. The ROC curve area for the ACB Test was 0.78 [95% confidence interval (CI), 0.70-0.86]. At the optimum decision point of 75 units/mL, the sensitivity and specificity of the ACB Test were 83% (95% CI, 66-93%) and 69% (95% CI, 62-76%). The negative predictive value was 96% (95% CI, 91-98%), and the positive predictive value was 33% (95% CI, 24-44%). The within-run CV of the ACB Test was 7.3%. Results for the reference population were normally distributed; the one-sided parametric 95th percentile was 80.2 units/mL.

CONCLUSIONS

This exploratory study suggests that the ACB Test has high negative predictive value and sensitivity in the presentation sample for predicting troponin-negative or -positive results 6-24 h later.