Rationale: Although IFN-g release assays (IGRAs) are widely used to screen for Mycobacterium tuberculosis infection in high-income countries, published data on repeatability are limited. Objectives: To determine IGRA repeatability. Methods: The study population included consecutive patients referred to The Methodist Hospital (Houston, TX) between August 1, 2010 and July 31, 2011 for latent tuberculosis (TB) infection screening with an IGRA (QuantiFERON-TB Gold In-Tube; Cellestis, Carnegie, Australia). We performed multiple IGRA tests using leftover stimulated plasma according to a prospectively formulated quality control protocol. We analyzed agreement in interpretation of test results classified according to manufacturer-recommended criteria and repeatability of quantitative TB response. Measurements and Main Results: During the study period, 1,086 test results were obtained from 543 subjects. Per the manufacturer's cutpoint, the result of the second test was discordant from that of the first in 28 (8%) of 366 patients with valid test results, including 13 with an initial negative result and 15 with an initial positive result. Although agreement between repeat test results was high (k ¼ 0.84; 95% confidence interval, 0.79-0.90), the normal expected range of within-subject variability in TB response on retesting included differences of 6 0.60 IU/ml for all individuals (coefficient of variation, 14%), and 6 0.24 IU/ml (coefficient of variation, 27%) for individuals whose initial TB response was between 0.25 and 0.80 IU/ml. Conclusions: There is substantial variability in TB response when IGRAs are repeated using the same patient sample. IGRA results should be interpreted cautiously when TB response is near interpretation cut-points.Keywords: interferon-g release assay; QuantiFERON; repeatability; imprecision IFN-g release assays (IGRAs) are in vitro immunodiagnostic tests that measure effector T cell-mediated IFN-g response to synthetic Mycobacterium tuberculosis-specific polypeptides. The QuantiFERON-TB Gold In-Tube (QFT-GIT; Cellestis, Carnegie, Australia) is a commercially available IGRA that has been recommended as an alternative to the tuberculin skin test (TST) in targeted screening for M. tuberculosis infection (1).Although IGRAs are widely used in high-income countries and numerous studies have evaluated their diagnostic performance, there are limited data on the precision of IGRA results. Clinically, such data are essential because treatment decisions could be impacted by interpretation of results close to the threshold for a positive test, and for changes above or below this threshold when serial testing is performed (2). Data on test imprecision, including repeatability (serial testing under identical conditions) and reproducibility (serial testing under changed conditions) (3) (see Table 1), are required for CE (Conformité Européene) Marking in the European Union and for premarket approval of in vitro diagnostic tests by the US Food and Drug Administration (FDA) (4).Repeatability is unaffected by inte...

ME. Circadian rhythms in myocardial metabolism and contractile function: influence of workload and oleate. Am J Physiol Heart Circ Physiol 293: H2385-H2393, 2007. First published July 6, 2007; doi:10.1152/ajpheart.01361.2006.-Multiple extracardiac stimuli, such as workload and circulating nutrients (e.g., fatty acids), known to influence myocardial metabolism and contractile function exhibit marked circadian rhythms. The aim of the present study was to investigate whether the rat heart exhibits circadian rhythms in its responsiveness to changes in workload and/or fatty acid (oleate) availability. Thus, hearts were isolated from male Wistar rats (housed during a 12:12-h light-dark cycle: lights on at 9 AM) at 9 AM, 3 PM, 9 PM, and 3 AM and perfused in the working mode ex vivo with 5 mM glucose plus either 0.4 or 0.8 mM oleate. Following 20-min perfusion at normal workload (i.e., 100 cm H 2O afterload), hearts were challenged with increased workload (140 cm H 2O afterload plus 1 M epinephrine). In the presence of 0.4 mM oleate, myocardial metabolism exhibited a marked circadian rhythm, with decreased rates of glucose oxidation, increased rates of lactate release, decreased glycogenolysis capacity, and increased channeling of oleate into nonoxidative pathways during the light phase. Rat hearts also exhibited a modest circadian rhythm in responsiveness to the workload challenge when perfused in the presence of 0.4 mM oleate, with increased myocardial oxygen consumption at the dark-to-light phase transition. However, rat hearts perfused in the presence of 0.8 mM oleate exhibited a markedly blunted contractile function response to the workload challenge during the light phase. In conclusion, these studies expose marked circadian rhythmicities in myocardial oxidative and nonoxidative metabolism as well as responsiveness of the rat heart to changes in workload and fatty acid availability. fatty acids; glucose; glycogen; triglyceride CIRCADIAN RHYTHMS IN CARDIOVASCULAR PHYSIOLOGY and pathophysiology are well established. Heart rate, blood pressure, cardiac output, platelet aggregability, myocardial infarction, arrhythmias, and sudden cardiac death all exhibit marked circadian rhythmicities in both humans and animal models (3,7,12,18,23,33). To date, these observations have been attributed primarily to diurnal variations in multiple extracellular stimuli (i.e., neurohumoral factors) such as autonomic and sympathetic activity (23,24,32). However, it is becoming increasingly clear that the intrinsic properties of cardiovascular components change over the course of the day, suggesting that oscillations in responsiveness to extracellular stimuli may contribute toward circadian rhythmicities in cardiovascular events (36, 37).Myocardial metabolism and contractile function are inextricably interlinked. For example, increased energy demand during periods of elevated workload is balanced by increased oxidative and nonoxidative metabolism (17). An inability of the heart to maintain adequate ATP supply will in turn adversely affect...

An ancestral polymorphic allele of the human autophagy-related gene IRGM1 is associated with altered gene expression and a genetic risk for Crohn's Disease (CD). We used the single nucleotide polymorphism rs10065172C/T as a marker of this polymorphic allele and genotyped 370 African American and 177 Caucasian tuberculosis (TB) cases and 180 African American and 110 Caucasian controls. Among African Americans, the TB cases were more likely to carry the CD-related T allele of rs10065172 (odds ratio of 1.54; 95% confidence interval, 1.17–2.02; P<0.01) compared to controls. Our finding suggests that this CD-related IRGM1 polymorphic allele is also associated with human susceptibility to TB disease among African Americans.

The intracellular circadian clock consists of a series of transcriptional modulators that together allow the cell to perceive the time of day. Circadian clocks have been identified within various components of the cardiovascular system (e.g. cardiomyocytes, vascular smooth muscle cells), and possess the potential to regulate numerous aspects of cardiovascular physiology and pathophysiology. The present study tested the hypothesis that ischemia/reperfusion (I/R; 30 minute occlusion of the rat left main coronary artery in vivo) alters the circadian clock within the ischemic, versus non-ischemic, region of the heart. Left ventricular anterior (ischemic) and posterior (non-ischemic) regions were isolated from I/R, sham-operated, and naïve rats over a 24 hour period, after which mRNAs encoding for both circadian clock components and known clock-controlled genes were quantified. Circadian clock gene oscillations (i.e. peak-to-trough fold differences) were rapidly attenuated in the I/R, versus the non-ischemic, region. Consistent with decreased circadian clock output, we observe a rapid induction of E4BP4 in the ischemic region of the heart at both the mRNA and protein levels. In contrast with I/R, chronic (1 week) hypobaric chamber-induced hypoxia did not attenuate oscillations in circadian clock genes in either the left or right ventricle of the rat heart. In conclusion, these data show that in a rodent model of myocardial I/R, circadian clocks within the ischemic region become rapidly impaired, through a mechanism that appears to be independent of hypoxia.