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Other Confounding Factors (other + confounding_factor)
Selected AbstractsGuidelines for improving the reproducibility of quantitative multiparameter immunofluorescence measurements by laser scanning cytometry on fixed cell suspensions from human solid tumorsCYTOMETRY, Issue 1 2006Stanley Shackney Abstract Background: Laser scanning Cytometry (LSC) is a versatile technology that makes it possible to perform multiple measurements on individual cells and correlate them cell by cell with other cellular features. It would be highly desirable to be able to perform reproducible, quantitative, correlated cell-based immunofluorescence studies on individual cells from human solid tumors. However, such studies can be challenging because of the presence of large numbers of cell aggregates and other confounding factors. Techniques have been developed to deal with cell aggregates in data sets collected by LSC. Experience has also been gained in addressing other key technical and methodological issues that can affect the reproducibility of such cell-based immunofluorescence measurements. Methods and results: We describe practical aspects of cell sample collection, cell fixation and staining, protocols for performing multiparameter immunofluorescence measurements by LSC, use of controls and reference samples, and approaches to data analysis that we have found useful in improving the accuracy and reproducibility of LSC data obtained in human tumor samples. We provide examples of the potential advantages of LSC in examining quantitative aspects of cell-based analysis. Improvements in the quality of cell-based multiparameter immunofluorescence measurements make it possible to extract useful information from relatively small numbers of cells. This, in turn, permits the performance of multiple multicolor panels on each tumor sample. With links among the different panels that are provided by overlapping measurements, it is possible to develop increasingly more extensive profiles of intracellular expression of multiple proteins in clinical samples of human solid tumors. Examples of such linked panels of measurements are provided. Conclusions: Advances in methodology can improve cell-based multiparameter immunofluorescence measurements on cell suspensions from human solid tumors by LSC for use in prognostic and predictive clinical applications. © 2005 Wiley-Liss, Inc. [source] Interactive effect of central obesity and hypertension on cognitive function in older out-patients with Type 2 diabetesDIABETIC MEDICINE, Issue 12 2008E. Kim Abstract Aim Central obesity, hypertension and diabetes mellitus have been related individually to cognitive dysfunction. We aimed to study the interactive effects of these co-occurring risk factors on cognitive decline, which remain unclear in older patients with diabetes. Methods We assessed metabolic profiles and neuropsychological functions in 60 older out-patients with Type 2 diabetes to examine the associations of central obesity with cognitive functions, while controlling for other confounding factors in these subjects. Results Waist circumference was associated with poor performance in digits forward (r2 = 0.11, P = 0.02), choice reaction time (r2 = 0.08, P = 0.04) and cognitive reaction time (r2 = 0.07, P < 0.05) even after adjustment for potential confounders including age, gender, education and HbA1c. There were also significant interactions between central obesity and hypertension with respect to performance of digits forward (P = 0.04) and delayed verbal cued recall (P = 0.03). Conclusion Our findings suggest that, in addition to glycaemic control, central obesity and hypertension influence cognitive functions, such as attention and psychomotor speed in older patients with Type 2 diabetes. [source] Glycaemic control in relation to xanthine oxidase and antioxidant indices in Malaysian Type 2 diabetes patientsDIABETIC MEDICINE, Issue 10 2005U. R. Kuppusamy Abstract Aims Increased oxidative stress and oxidative damage are present in Type 2 diabetes mellitus (DM). The aim of this study was to assess the oxidative stress levels in the three major ethnic groups in Malaysia and to study the association between glycaemic control and oxidant,antioxidant levels in these patients. Methods Oxidative indices and glycaemic control were assessed in 650 Type 2 DM patients and 280 healthy age-matched controls by known established methods. Results Type 2 DM patients had significantly lower levels of antioxidant enzymes and non-enzymatic antioxidant (FRAP) and increased levels of HbA1c, fasting blood glucose (FBG), malondialdehyde (MDA) and xanthine oxidase (XO) when compared with control subjects. Markers of oxidative stress were more apparent in Indian patients compared with Malay and Chinese patients. Correlation analysis of oxidant,antioxidant parameters as a function of HbA1c in each ethnic group revealed a strong association of HbA1c with oxidative indices. Conclusions The present study provides evidence for the possible contribution of XO to oxidative stress and the pathophysiology of diabetes. HbA1c remains an important marker of glycaemic control for the management of Type 2 DM, but other confounding factors that predispose or lead to oxidative stress should also be taken into consideration. [source] Does versatility as measured by geographic range, bathymetric range and morphological variability contribute to taxon longevity?GLOBAL ECOLOGY, Issue 1 2007Lee Hsiang Liow ABSTRACT Aim, This paper aims to examine the relationship between versatility as measured by geographic range, bathymetric range and morphological variability (species and subspecies richness and the occurrence of morphologically highly variable populations), and the geologic longevities of trachyleberidid ostracode species and genera, while accounting for sampling biases and other confounding factors. Location, Global. Methods, A large database of occurrence records of species of the family Trachyleberididae s.l. was analysed. The relationships between genus and species longevity and the above mentioned variables were examined singly and in concert. Re-analyses of subsets of data and rarefaction techniques were employed to account for sampling biases, while randomization was used to account for autocorrelation of variables. Results, The mean number of occurrence records, and latitudinal and longitudinal ranges, were strongly and positively correlated with genus and species longevities. The number of bathymetric zones occupied by genera had no consistent bearing on their longevities, but species data subsets tended to indicate significant positive relationships between bathymetric range and longevities. Species richness was significantly and positively correlated with genus longevities. Species and genera with subspecies and species with high morphological variability all had significantly greater longevities. Genus-level characteristics can be explained largely by species-level characteristics, including longevity, latitudinal ranges and bathymetric ranges to a lesser degree. However, genus longevity was best explained by species richness and genus age, even for extinct genera, while species longevity was best explained by species latitudinal range. Main conclusions, In spite of the incompleteness of the fossil record, we can control for biasing factors and still confidently draw the conclusion that both ecological and evolutionary versatility contribute to lineage longevity, beyond the shorter temporal observation windows available to most ecological studies. [source] The occurrence of commensal rodents in dwellings as revealed by the 1996 English House Condition SurveyJOURNAL OF APPLIED ECOLOGY, Issue 4 2001S.D. Langton Summary 1,The presence of commensal rodents was assessed in the 1996 English House Condition Survey (EHCS). Logistic regression techniques were used to identify the key factors that might determine the susceptibility of dwellings to infestation. 2,The overall percentages of dwellings that were infested, weighted to allow for the more intensive sampling used in certain categories of dwellings, were 1·83% for mice Mus domesticus, 0·23% for rats Rattus norvegicus living indoors and 1·60% for rats living outdoors. These figures excluded vacant properties, properties with some commercial use, and purpose-built flats, as these groups showed different patterns of infestation and were therefore excluded from the logistic regressions. 3,The prevalence of both rats and mice was significantly greater for dwellings where pets or livestock were kept in the garden. 4,Dwellings classed as unfit for human habitation were more likely to be infested with mice. 5,Dwellings in areas of low-density housing had a significantly higher prevalence of both rat and mouse infestation. This probably reflects the general suitability of the rural environment for commensal rodents. 6,Older properties had a relatively high prevalence of rats. This may be because their mature gardens provided suitable habitats for colonization. Once other confounding factors were taken into account, the age of the property did not influence the rate of infestation by mice. 7,Dwellings in areas with substantial problems, such as dereliction, litter, vacant properties and unkempt gardens, had a significantly higher prevalence of rats and mice. 8,This study reveals the value of applied ecological techniques, including logistic regression of presence,absence data, in understanding the distribution of commensal rodents in relation to dwellings, with the prospect of more effective management practices being developed as a consequence. [source] Nonreplication in Genetic Studies of Complex Diseases,Lessons Learned From Studies of Osteoporosis and Tentative Remedies,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 3 2005Hui Shen Abstract Inconsistent results have accumulated in genetic studies of complex diseases/traits over the past decade. Using osteoporosis as an example, we address major potential factors for the nonreplication results and propose some potential remedies. Over the past decade, numerous linkage and association studies have been performed to search for genes predisposing to complex human diseases. However, relatively little success has been achieved, and inconsistent results have accumulated. We argue that those nonreplication results are not unexpected, given the complicated nature of complex diseases and a number of confounding factors. In this article, based on our experience in genetic studies of osteoporosis, we discuss major potential factors for the inconsistent results and propose some potential remedies. We believe that one of the main reasons for this lack of reproducibility is overinterpretation of nominally significant results from studies with insufficient statistical power. We indicate that the power of a study is not only influenced by the sample size, but also by genetic heterogeneity, the extent and degree of linkage disequilibrium (LD) between the markers tested and the causal variants, and the allele frequency differences between them. We also discuss the effects of other confounding factors, including population stratification, phenotype difference, genotype and phenotype quality control, multiple testing, and genuine biological differences. In addition, we note that with low statistical power, even a "replicated" finding is still likely to be a false positive. We believe that with rigorous control of study design and interpretation of different outcomes, inconsistency will be largely reduced, and the chances of successfully revealing genetic components of complex diseases will be greatly improved. [source] Mode of HIV transmission associated with risk of oral lesions in HIV-infected subjects in ThailandJOURNAL OF ORAL PATHOLOGY & MEDICINE, Issue 2 2010W. Nittayananta J Oral Pathol Med (2010) 39 195,200 Background:, The aim of this study was to determine if route of human immunodeficiency virus (HIV) transmission is associated with the risk of oral lesions in HIV-infected subjects in Thailand. Methods:, A cross-sectional study was performed in 186 HIV-infected heterosexuals (aged 21,65 years, mean 32 years), and 82 HIV-infected intravenous drug users (IVDUs) (aged 16,50 years, mean 30 years). The following information was recorded: route of HIV transmission, total lymphocyte cell counts, weight, smoking habit, alcohol consumption, medications, presence of denture, plaque index, and presence of oral lesions. The association between mode of HIV transmission and the risk of oral lesions among the subjects was determined by multiple logistic regression analysis. Results:, Oral lesions were found in 138 HIV-infected heterosexuals (75%) and in 37 HIV-infected IVDUs (46%). Oral candidiasis (OC) was the most common lesion among both groups (44% vs. 28%), followed by hairy leukoplakia (HL) (33% vs. 10%). Multiple logistic regression analysis showed a significant association between mode of HIV transmission and the risk of oral lesions after controlling for the total lymphocyte cell counts and other confounding factors [OR 3.1; 95% CI 1.5,6.4; P = 0.002]. OC was significantly associated with heterosexual route of HIV transmission [OR 2.4; 95% CI 1.2,4.7; P = 0.014]. Similar association was also observed with HL [OR 3.7; 95% CI 1.5,9.1; P = 0.004]. Conclusions:, Mode of HIV transmission is associated with the risk of oral lesions in HIV-infected subjects in Thailand. Further studies should be performed to determine if the risk of oral lesions is associated with differences in HIV-subtypes. [source] Prevalence of diabetes mellitus and insulin resistance in patients with chronic hepatitis C: comparison with hepatitis B virus-infected and hepatitis C virus-cleared patientsLIVER INTERNATIONAL, Issue 3 2008Fumio Imazeki Abstract Background/Aims: Our aim was to evaluate the relationship between hepatitis C virus (HCV) infection and development of diabetes mellitus (DM) or insulin resistance (IR) in comparison with hepatitis B virus (HBV) infection and eradication of HCV infection by interferon treatment. Methods: This study consisted of 952 outpatients, including 544 HCV-infected (HCV+chronic), 286 HBV-infected (HBV+chronic) and 122 patients whose HCV was cleared by interferon treatment (HCV+cleared) (diabetes study). Among 849 without overt DM, IR was assessed in 423 patients, including 232 HCV-infected (HCV+chronic), 135 HBV-infected (HBV+chronic) and 56 HCV-eradicated patients (HCV+cleared) (IR substudy). Results: The prevalence of DM in the HBV+chronic, HCV+chronic and HCV+cleared groups was 6.3, 13.6 and 9.0%, respectively (HBV+chronic vs HCV+chronic, P<0.005), in the diabetes study, and the prevalence of IR in the HCV+chronic group (54.3%) was also higher than that in the HBV+chronic (36.3%) (P<0.005) and HCV+cleared groups (35.7%) (P<0.05) in the IR substudy. However, HCV infection was not shown to be independently associated with DM development [odds ratio (OR) 1.669; P=0.0936] and with IR (OR 1.531; P=0.2154) by multivariate analysis in comparison with HBV infection as control. Conclusions: HCV-infected patients showed a higher prevalence of DM and IR than those with HBV infection. However, in Japan, other confounding factors appeared to be more important risk factors for the development of disturbance in glucose metabolism. [source] Essential tremor , Neurodegenerative or nondegenerative disease towards a working definition of ET,MOVEMENT DISORDERS, Issue 14 2009Günther Deuschl MD Abstract Essential tremor (ET) is a syndrome of tremor in posture and movement, but recent studies have revealed additional cerebellar motor disturbances, cognitive disturbances, personality changes, hearing loss, and olfactory deficits. Even dementia and shortened life expectancy were found in one cohort. Recent postmortem studies have found limited Lewy body pathology in some patients and Purkinje cell loss with torpedoes and Bergmann gliosis in others. These findings have led to the hypothesis that ET is a syndrome produced by at least two neurodegenerative diseases with more widespread clinical consequences than previously appreciated. We review the evidence for and against this hypothesis and conclude that studies purporting to support this hypothesis have failed to control for age-associated comorbidities, depression, medications, and other confounding factors. We propose the alternative hypothesis that abnormal neuronal oscillation is the fundamental abnormality in ET, and the well-documented cerebellar signs and symptoms, the controversial non-motor signs, and even the cerebellar pathology of ET could be caused by this oscillation. A major problem for many studies is the lack of a diagnostic gold standard. Lacking such a standard, we propose a subclassification of ET into three categories: hereditary ET, sporadic ET, and senile ET, which we believe will help researchers resolve many of the controversies in this field. © 2009 Movement Disorder Society [source] |