Critical appraisal of four IL-6 immunoassays.

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BACKGROUND: Interleukin-6 (IL-6) contributes to numerous inflammatory, metabolic, and physiologic pathways of disease. We evaluated four IL-6 immunoassays in order to identify a reliable assay for studies of metabolic and physical function. Serial plasma samples from intravenous glucose tolerance tests (IVGTTs), with expected rises in IL-6 concentrations, were used to test the face validity of the various assays. METHODS AND FINDINGS: IVGTTs, administered to 14 subjects, were performed with a single infusion of glucose (0.3 g/kg body mass) at time zero, a single infusion of insulin (0.025 U/kg body mass) at 20 minutes, and frequent blood collection from time zero to 180 minutes for subsequent Il-6 measurement. The performance metrics of four IL-6 detection methods were compared: Meso Scale Discovery immunoassay (MSD), an Invitrogen Luminex bead-based multiplex panel (LX), an Invitrogen Ultrasensitive Luminex bead-based singleplex assay (ULX), and R&D High Sensitivity ELISA (R&D). IL-6 concentrations measured with MSD, R&D and ULX correlated with each other (Pearson Correlation Coefficients r = 0.47-0.94, p<0.0001) but only ULX correlated (r = 0.31, p = 0.0027) with Invitrogen Luminex. MSD, R&D, and ULX, but not LX, detected increases in IL-6 in response to glucose. All plasma samples were measurable by MSD, while 35%, 1%, and 4.3% of samples were out of range when measured by LX, ULX, and R&D, respectively. Based on representative data from the MSD assay, baseline plasma IL-6 (0.90 ± 0.48 pg/mL) increased significantly as expected by 90 minutes (1.29 ± 0.59 pg/mL, p = 0.049), and continued rising through 3 hours (4.25 ± 3.67 pg/mL, p = 0.0048). CONCLUSION: This study established the face validity of IL-6 measurement by MSD, R&D, and ULX but not LX, and the superiority of MSD with respect to dynamic range. Plasma IL-6 concentrations increase in response to glucose and insulin, consistent with both an early glucose-dependent response (detectable at 1-2 hours) and a late insulin-dependent response (detectable after 2 hours).





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Thompson, Dana K, Kim M Huffman, William E Kraus and Virginia Byers Kraus (2012). Critical appraisal of four IL-6 immunoassays. PLoS One, 7(2). p. e30659. 10.1371/journal.pone.0030659 Retrieved from

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Kim Marie Huffman

Associate Professor of Medicine

Determining the role of physical activity in modulating health outcomes (cardiovascular disease risk) in persons with rheumatologic diseases (rheumatoid arthritis, gout, osteoarthritis)

Integrating clinical rheumatology, basic immunology, metabolism, and exercise science in order to reduce morbidity in individuals with arthritis

Evaluating relationships between circulating and intra-muscular metabolic intermediates and insulin resistance in sedentary as well as individuals engaging in regular exercise

Addressing the role of physical activity in modulating inflammation, metabolism, and functional health in aging populations


William Erle Kraus

Richard and Pat Johnson University Distinguished Professor

My training, expertise and research interests range from human integrative physiology and genetics to animal exercise models to cell culture models of skeletal muscle adaptation to mechanical stretch. I am trained clinically as an internist and preventive cardiologist, with particular expertise in preventive cardiology and cardiac rehabilitation.  My research training spans molecular biology and cell culture, molecular genetics, and integrative human exercise physiology and metabolism. I practice as a preventive cardiologist with a focus on cardiometabolic risk and exercise physiology for older athletes.  My research space has both a basic wet laboratory component and a human integrative physiology one.

One focus of our work is an integrative physiologic examination of exercise effects in human subjects in clinical studies of exercise training in normal individuals, in individuals at risk of disease (such as pre-diabetes and metabolic syndrome; STRRIDE), and in individuals with disease (such as coronary heart disease, congestive heart failure and cancer).

A second focus of my research group is exploration of genetic determinates of disease risk in human subjects.  We conduct studies of early onset cardiovascular disease (GENECARD; CATHGEN), congestive heart failure (HF-ACTION), peripheral arterial disease (AMNESTI), and metabolic syndrome.  We are exploring analytic models of predicting disease risk using established and innovative statistical methodology.

A third focus of my group’s work is to understand the cellular signaling mechanisms underlying the normal adaptive responses of skeletal muscle to physiologic stimuli, such as occur in exercise conditioning, and to understand the abnormal maladaptive responses that occur in response to pathophysiologic stimuli, such as occur in congestive heart failure, aging and prolonged exposure to microgravity.

Recently we have begun to investigate interactions of genes and lifestyle interventions on cardiometabolic outcomes.  We have experience with clinical lifestyle intervention studies, particularly the contributions of genetic variants to interventions responses.  We call this Lifestyle Medicopharmacogenetics.


exercise, skeletal muscle, energy metabolism, cell signaling, gene expression, cell stretch, heart failure, aging, spaceflight, human genetics, early onset cardiovascular disease, lifestyle medicine


Virginia Byers Kraus

Mary Bernheim Distinguished Professor of Medicine

Virginia Byers Kraus, MD, PhD, is the Mary Bernheim Distinguished Professor of Medicine, Professor of Orthopaedic Surgery, Professor of Pathology and a faculty member of the Duke Molecular Physiology Institute in the Duke University School of Medicine. She is a practicing Rheumatologist with over 30 years’ experience in translational musculoskeletal research focusing on osteoarthritis, the most common of all arthritides. She trained at Brown University (ScB 1979), Duke University (MD 1982, PhD 1993) and the Duke University School of Medicine (Residency in Internal Medicine and Fellowship in Rheumatology). Her career has focused on elucidating osteoarthritis pathogenesis and translational research into the discovery and validation of biomarkers for early osteoarthritis detection, prediction of progression, monitoring of disease status, and facilitation of therapeutic developments. She is co-PI of the Foundation for NIH Biomarkers Consortium Osteoarthritis project. Trained as a molecular biologist and a Rheumatologist, she endeavors to study disease from bedside to bench.

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