Clinical Abstracts
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April 2012 Editors:
Diabetes mellitus and chronic kidney disease are risk factors for developing cardiovascular events. It is not known whether better glycemic control can impact clinical outcomes such as all-cause-mortality, cardiovascular events, hospitalizations, and kidney failure in people with diabetes mellitus and stage 3 to 4 chronic kidney disease (CKD). Most previous trials of glycemic control have excluded those patients with reduced glomerular filtration rate (GFR), so present targets for HbA1C of seven percent for all patients with or without kidney disease is not well substantiated. The authors performed a retrospective population-based cohort study to assess glycemic control relative to clinical outcomes. The study included patients with serum creatinine measured as part of routine care for CKD. Patients with an estimated GFR (eGFR) of less than 60 mL/min./1.73 m2 and diabetes mellitus were classified based on their first HbA1C measurement. The authors assessed HbA1C levels and five clinical outcomes for independent association using the Cox regression model, death, progression of kidney disease, new end-stage renal disease, cardiovascular events, and all-cause hospitalization. The study results from 23,296 patients with diabetes mellitus and a low GFR showed that the median HbA1C level was 6.9 percent (range, 2.8 percent to 20 percent) and only 11 percent of the subjects had an HbA1C value higher than nine percent. During the median followup period of 3.8 years, a higher HbA1C of more than eight percent was shown to be strongly and independently associated with all five clinical outcomes: 16 percent of patients died, 49 percent were hospitalized, 16 percent had cardiovascular events, six percent had doubling of serum creatinine value, and two percent developed end-stage renal disease. Interestingly, very restrictive HbA1C values of less than 6.5 percent in people with stage 3 to 4 CKD were also associated with excess mortality. The authors noted that this association with adverse macrovascular outcomes in patients with diabetes mellitus and CKD may be due to serious hypoglycemic events or too precipitous of a fall in average glucose. Alternatively, there may be a point of no return for kidney function, where better glycemic control may not prevent further kidney loss. Shurraw S, Hemmelgarn B, Lin M, et al. Association between glycemic control and adverse outcomes in people with diabetes mellitus and chronic kidney disease. Arch Intern Med. 2011;171(21):1920–1927. Correspondence: Dr. Marcello Tonelli at mtonelli-admin@med.ualberta.ca [ Top ]
Growth differentiation factor-15 (GDF-15) is a transforming growth factor that is secreted by cardiomyocytes, activated macrophages, endothelial cells, vascular smooth muscle cells, and adipocytes. Of interest are ex vivo and in vivo murine and human cardiomyocyte models that have shown upregulation of GDF-15 in response to stresses such as myocardial infarction and ischemia. GDF-15 has paracrine effects, which reduce infarct size and induce apoptosis and hypertrophy. Previous studies have evaluated GDF-15 in high-risk populations with ischemic heart disease and have shown increasing levels of GDF-15 in association with total and cardiovascular mortality but inconsistently with nonfatal myocardial infarctions. Many previous studies were performed on elderly people with a normal or borderline body mass index. This is the first study to evaluate concentrations of GDF-15 in a somewhat younger, healthier population of middle age, ethnically diverse, adults. The authors used the cohort from the Dallas Heart Study to evaluate the associations between plasma concentrations of GDF-15 and subclinical coronary atherosclerosis and mortality. They discovered that increasing GDF-15 concentrations were associated with prevalent coronary artery calcium (CAC) and increased CAC (100 or more Agatston units). Age was the variable most strongly correlated with GDF-15. Increasing GDF-15 was also associated with black race, hypertension, diabetes, smoking, left ventricular mass/body surface area, and worsening renal function. This study showed that after a median followup of 7.3 years, there were 120 deaths from cardiovascular disease. In Cox proportional hazards models adjusting for variables, participants with GDF-15 concentrations of 1,800 ng/L or more were at increased risk for all-cause and cardiovascular death compared with those subjects who had GDF-15 concentrations of less than 1,200 ng/L. The authors concluded that whether or not GDF-15 contributes directly to atherosclerosis is unknown. However, GDF-15 potentially may be a useful biomarker for cardiovascular disease. Rohatgi A, Patel P, Das SR, et al. Association of growth differentiation factor-15 with coronary atherosclerosis and mortality in a young multiethnic population: observations from the Dallas Heart Study. Clin Chem. 2012;58(1):172–182. Correspondence: Anand Rohatgi at anand.rohatgi@utsouthwestern.edu [ Top ]
Respiratory disease in pigs is the most important health concern for swine producers. According to the 2006 National Animal Health Monitoring System survey, respiratory disease was the greatest cause of mortality in swine, accounting for 53.7 percent of nursery deaths and 60.1 percent of deaths in grower/finisher pigs. The top viral pathogens affecting U.S. swine herds are porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV), swine influenza virus (SwIV), porcine circovirus type 2 (PCV2), and porcine respiratory coronavirus (PRCV). PRRS was first recognized in the United States in 1987. Since then, PRRS has become the leading swine disease problem in the United States, causing an estimated $570 million annual loss. The causative agent, PRRSV, is a single-stranded positive-sense RNA virus classified as a member of the genus Arterivirus, family Arteriviridae, and order Nidovirales. Due to its high mutation rate and genetic variability, even among viruses within the same genotype, PRRSV is difficult to control and remains the foremost contributor to swine respiratory disease. Accordingly, PRRS is an example of a continually emerging viral disease affecting swine and causing devastating effects on the industry. Several factors have recently converged, elevating the need for highly parallel diagnostic platforms that can detect many known, novel, and emerging pathogenic agents simultaneously. Panviral DNA microarrays represent the most robust approach for massively parallel viral surveillance and detection. Virochip is a panviral DNA microarray that can detect all known viruses, as well as novel viruses related to known viral families, in a single assay. It has been used to identify known and novel viral agents in clinical human specimens. However, the usefulness and sensitivity of the Virochip platform have not been tested on a set of clinical veterinary specimens with the high degree of genetic variance that is frequently observed with swine field isolates. The authors investigated the utility and sensitivity of Virochip for detecting swine viruses in cell culture-derived samples and clinical swine samples. Virochip detected porcine PRRSV in serum containing 6.10 102 viral copies/µL and influenza A virus in lung lavage fluid containing 2.08 106 viral copies/µL. Virochip also detected PCV2 in serum containing 2.50 108 viral copies/µL and PRCV in turbinate tissue homogenate. The authors concluded that, collectively, the data in this report demonstrate that Virochip can detect pathogenic viruses frequently found in swine in a variety of solid and liquid specimens, such as turbinate tissue homogenate and lung lavage fluid, as well as in antemortem samples, such as serum. Nicholson TL, Kukielka D, Vincent AL, Brock- meier SL, et al. Utility of a panviral microarray for detection of swine respiratory viruses in clinical samples. J Clin Microbiol. 2011;49:1542–1548. Correspondence: Tracy L. Nicholson at tracy.nicholson@ars.usda.gov [ Top ]
Epidemiologic evidence suggests that inflammation may be an underlying mechanism in the development of ovarian cancer. The chronic inflammatory state is characterized by dysregulation of cytokine secretion, thereby increasing the likelihood of excessive cell growth, malignant transformation, and survival of transformed cells. Cytokines can promote the secretion of other cytokines and regulate the expression of their soluble receptors/modulators. Therefore, the authors hypothesized that cytokines and cytokine modulators are associated with increased risk of ovarian cancer. To date, the only biomarker of inflammation that has been examined in relation to the development of ovarian cancer is C-reactive protein (CRP). One study found that women with CRP levels in the highest third of the distribution had a 70 percent increased risk of ovarian cancer versus women in the lowest third, though a second study conducted by the authors’ group found the association only among women with the highest CRP levels (greater than 10 mg/L). The authors conducted a study to assess the relationship between inflammatory cytokines (IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL12p70, IL-13, and TNFα) and cytokine modulators (IL-1Ra, sIL-1RII, sIL-2Ra, sIL-4R, sIL-6R, IL-12p40, and sTNF-R1/R2) and subsequent risk of epithelial ovarian cancer. The case-control study was nested within three prospective cohort studies—the New York University Women’s Health Study, Northern Sweden Health and Disease Study, and Italian Hormones and Diet in the Etiology of Cancer Study. Markers were selected on the basis of their biological relevance to normal and malignant ovarian processes and adequate temporal reproducibility over a two- to three-year period in preliminary reliability studies. The study featured herein involved 230 cases and 432 individually matched controls nested within the three prospective cohorts and measured biomarkers using Luminex xMap technology. The authors observed a trend across quartiles for IL-2 (odds ratio [OR] Q4 vs Q1, 1.57; 95 percent confidence interval [CI], 0.98–2.52; P=0.07), IL-4 (OR Q4 vs Q1, 1.50; 95 percent CI, 0.95–2.38; P=0.06), IL-6 (OR Q4 vs Q1, 1.63; 95 percent CI, 1.03–2.58; P=0.03), IL-12p40 (OR Q4 vs Q1, 1.60; 95 percent CI, 1.02–2.51; P=0.06), and IL-13 (OR Q4 vs Q1, 1.42; 95 percent CI, 0.90–2.26; P=0.11). Trends were also observed when cytokines were modeled on the continuous scale for IL-4 (P=0.01), IL-6 (P=0.01), IL-12p40 (P=0.01), and IL-13 (P=0.04). Odds ratios were not materially different after excluding cases diagnosed less than five years after blood donation or when limited to serous tumors. The authors concluded that this study provides direct evidence that multiple inflammation markers, specifically IL-2, IL-4, IL-6, IL-12, and IL-13, may be associated with risk of epithelial ovarian cancer and adds to evidence that inflammation is involved in development of this disease. Clendenen TV, Lundin E, Zeleniuch-Jacquotte A, et al. Circulating inflammation markers and risk of epithelial ovarian cancer. Cancer Epidemiol Biomarkers Prev. 2011;20: 799–810. Correspondence: Tess V. Clendenen at tess.clendenen@nyumc.org [ Top ]
Concerns about the performance of cardiac troponin assays have been reported previously for several platforms. It has been observed that Beckman Coulter’s Unicel DxI AccuTnI assay sometimes yielded nonreproducible falsely increased results on some plasma samples. These Tn false-positives were identified by the finding of substantially lower values on re-analysis after recentrifugation in a high-speed microcentrifuge, suggesting that particulate matter could play a role in generating the erroneous result. However, while recentrifuging and repeating every sample with an elevated TnI concentration became an effective tool to prevent reporting false-positive results, the practice was laborious, difficult to automate, wasteful of reagents, and associated with a lengthy turnaround time. Beckman Coulter and Becton Dickinson (marketer of the lithium-heparin plasma separator tube [PST]) suggested that the problem could be minimized by thoroughly mixing heparin anticoagulant into samples by repeatedly inverting the tube immediately after phlebotomy. However, getting hurried lab staff to adhere to proper technique was thought to be difficult because such a technique slows the process of obtaining specimens and is especially awkward when drawing multiple specimens. A solution that was independent of human factors was thought to have a greater chance of success. The authors hypothesized that switching from lithium-heparin plasma to serum could ameliorate this problem by avoiding incomplete or delayed coagulation. In addition, platelets and cell fragments that do not readily penetrate separator gels could be removed by incorporating them into the forming clot. Because standard protocols for preparing serum for testing include a lengthy coagulation period that is incompatible with the requirements of stat testing, the authors investigated whether the Becton Dickinson Vacutainer rapid serum tubes (RSTs) could provide rapid and reliable TnI results when assayed on the Beckman DxI platform and whether using these tubes in the routine hospital setting would reduce the rate of false-positive results. Patients being evaluated for suspected myocardial infarction had specimens drawn into an RST and into the standard lithium-heparin plasma separator tube. The authors measured 28 separate analytes in both specimens using immunoassay and electrochemical and spectrophotometric methods. Higher results were observed in some PST specimens tested for troponin I, creatine kinase-MB isoenzyme, human chorionic gonadotropin, and thyroid-stimulating hormone. These discrepancies were investigated by repeating analyses after recentrifugation of both specimens. Re-analysis gave results for the PST specimens that were lower and agreed well with initial results from RSTs, suggesting false-positive rates of 10.8 percent for troponin I and about two percent for each of the other three analytes. Overall, specimens collected in RSTs had fewer false-positive immunoassay results than specimens collected in plasma separator tubes. Strathmann FG, Ka MM, Rainey PM, et al. Use of the BD Vacutainer rapid serum tube reduces false-positive results for selected Beckman Coulter Unicel DxI immunoassays. Am J Clin Pathol. 2011;136:325–329. Correspondence: Dr. Geoffrey S. Baird, Laboratory Medicine, University of Washington, Harborview Medical Center, Box 359743, 325 9th Ave., Seattle, WA 98104 [ Top ]Clinical pathology abstracts editors: Deborah Sesok-Pizzini, MD, MBA, associate professor, Department of Clinical Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, and medical director, Blood Bank and Transfusion Medicine, Children's Hospital of Philadelphia; Michael Bissell, MD, PhD, MPH, professor, Department of Pathology, Ohio State University, Columbus. |
