83 resultados para sample size


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OBJECTIVES: The human immunodeficiency virus protease inhibitor nelfinavir is substrate of polyspecific drug transporters encoded by ABCB1 (P-glycoprotein), ABCC1 (MRP1) and ABCC2 (MRP2), and an inhibitor of BCRP, encoded by ABCG2. Genetic polymorphism in these genes may be associated with changes in transport function. METHODS: A comprehensive evaluation of single nucleotide polymorphisms (39 SNPs in ABCB1, 7 in ABCC1, 27 in ABCC2, and 16 in ABCG2), and inferred haplotypes was done to assess possible associations of genetic variants with cellular exposure of nelfinavir in vivo. Analysis used peripheral mononuclear cells from individuals receiving nelfinavir (n=28). Key results were re-examined in a larger sample size (n=129) contributing data on plasma drug levels. RESULTS AND CONCLUSIONS: There was no significant association between cellular nelfinavir area under the curve (AUC) and SNPs or haplotypes at ABCC1, ABCC2, ABCG2. There was an association with cellular exposure for two loci in strong linkage disequilibrium: ABCB1 3435C>T; AUCTT>AUCCT>AUCCC (ratio 2.1, 1.4, 1, Ptrend=0.01), and intron 26 +80T>C; AUCCC> AUCCT > AUCTT (ratio 2.4, 1.3, 1, Ptrend=0.006). Haplotypic analysis using tagging SNPs did not improve the single SNP association values.

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ABSTRACT: BACKGROUND: Serum protein S-100B determinations have been widely proposed in the past as markers of traumatic brain injury and used as a predictor of injury severity and outcome. The purpose of this prospective observational case series was therefore to determine S-100B serum levels in patients with isolated injuries to the back. METHODS: Between 1 February and 1 May 2008, serum samples for S-100B analysis were obtained within 1 hour of injury from 285 trauma patients. All patients with a head injury, polytrauma, and intoxicated patients were excluded to select isolated injuries to the spine. 19 patients with isolated injury of the back were included. Serum samples for S-100B analysis and CT spine were obtained within 1 hours of injury. RESULTS: CT scans showed vertebral fractures in 12 of the 19 patients (63%). All patients with fractures had elevated S-100B levels. Amongst the remaining 7 patients without a fracture, only one patient with a severe spinal contusion had an S-100B concentration above the reference limit. The mean S-100B value of the group with fractures was more than 4 times higher than in the group without fractures (0.385 vs 0.087 mug/L, p = 0.0097). CONCLUSION: Our data, although limited due to a very small sample size, suggest that S-100B serum levels might be useful for the diagnosis of acute vertebral body and spinal cord injury with a high negative predictive power. According to the literature, the highest levels of serum S-100B are found when large bones are fractured. If a large prospective study confirms our findings, determining the S-100B level may contribute to more selective use of CT and MRI in spinal trauma.

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BACKGROUND: Not all clinical trials are published, which may distort the evidence that is available in the literature. We studied the publication rate of a cohort of clinical trials and identified factors associated with publication and nonpublication of results. METHODS: We analysed the protocols of randomized clinical trials of drug interventions submitted to the research ethics committee of University Hospital (Inselspital) Bern, Switzerland from 1988 to 1998. We identified full articles published up to 2006 by searching the Cochrane CENTRAL database (issue 02/2006) and by contacting investigators. We analyzed factors associated with the publication of trials using descriptive statistics and logistic regression models. RESULTS: 451 study protocols and 375 corresponding articles were analyzed. 233 protocols resulted in at least one publication, a publication rate of 52%. A total of 366 (81%) trials were commercially funded, 47 (10%) had non-commercial funding. 346 trials (77%) were multi-centre studies and 272 of these (79%) were international collaborations. In the adjusted logistic regression model non-commercial funding (Odds Ratio [OR] 2.42, 95% CI 1.14-5.17), multi-centre status (OR 2.09, 95% CI 1.03-4.24), international collaboration (OR 1.87, 95% CI 0.99-3.55) and a sample size above the median of 236 participants (OR 2.04, 95% CI 1.23-3.39) were associated with full publication. CONCLUSIONS: In this cohort of applications to an ethics committee in Switzerland, only about half of clinical drug trials were published. Large multi-centre trials with non-commercial funding were more likely to be published than other trials, but most trials were funded by industry.

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BACKGROUND: Acne inversa is a chronic inflammatory disorder of apocrine gland-bearing skin. The role of the innate immune system in the pathogenesis of the disease is controversial. OBJECTIVES: We investigated the expression of antimicrobial peptide/proteins in acne inversa. METHODS: Tissue samples were obtained from patients with acne inversa and compared with normal-appearing skin. The expression of psoriasin and human beta-defensin (hBD)-2 on messenger RNA and protein level was analyzed. RESULTS: Both messenger RNA and protein levels of psoriasin and hBD-2 were significantly increased in acne inversa. Macrophages expressing hBD-2 were found in the dermis. LIMITATIONS: Small sample size is a limitation. CONCLUSIONS: Antimicrobial peptide/proteins are overexpressed in acne inversa lesions as compared with normal-appearing skin. The site of the major expression depends on the particular antimicrobial peptide/protein. Psoriasin is overexpressed in epidermal keratinocytes whereas hBD-2 is produced mainly by dermal macrophages, leaving a relative deficiency of hBD-2 in the epidermis of acne inversa lesions.

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BACKGROUND: Current international treatment guidelines recommending therapeutic exercise for people with symptomatic hip OA report are based on expert opinion only. OBJECTIVES: To determine whether land-based therapeutic exercise is beneficial for people with hip OA in terms of reduced joint pain and/or improved physical function. SEARCH STRATEGY: Five databases were searched from 1966 up until August 2008. SELECTION CRITERIA: All randomised controlled trials (RCTs) recruiting people with hip OA and comparing some form of land-based therapeutic exercise (as opposed to exercises conducted in the water) with a non-exercise group. DATA COLLECTION AND ANALYSIS: Three reviewers independently extracted data and assessed methodological quality. All analyses were conducted on continuous outcomes. MAIN RESULTS: Combining the results of the five included RCTs demonstrated a small treatment effect for pain, but no benefit in terms of improved self-reported physical function. Only one of these five RCTs exclusively recruited people with symptomatic hip OA. AUTHORS' CONCLUSIONS: The limited number and small sample size of the included RCTs restricts the confidence that can be attributed to these results. Adequately powered RCTs evaluating exercise programs specifically designed for people with symptomatic hip OA need to be conducted.

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BACKGROUND: Enquiries among patients on the one hand and experimental and observational studies on the other suggest an influence of stress on inflammatory bowel diseases (IBD). However, since this influence remains hypothetical, further research is essential. We aimed to devise recommendations for future investigations in IBD by means of scrutinizing previously applied methodology. METHODS: We critically reviewed prospective clinical studies on the effect of psychological stress on IBD. Eligible studies were searched by means of the PubMed electronic library and through checking the bibliographies of located sources. RESULTS: We identified 20 publications resulting from 18 different studies. Sample sizes ranged between 10 and 155 participants. Study designs in terms of patient assessment, control variables, and applied psychometric instruments varied substantially across studies. Methodological strengths and weaknesses were irregularly dispersed. Thirteen studies reported significant relationships between stress and adverse outcomes. CONCLUSIONS: Study designs, including accuracy of outcome assessment and repeated sampling of outcomes (i.e. symptoms, clinical, and endoscopic), depended upon conditions like sample size, participants' compliance, and available resources. Meeting additional criteria of sound methodology, like taking into account covariates of the disease and its course, is strongly recommended to possibly improve study designs in future IBD research.

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Acute infection with the hepatitis C virus (HCV) induces a wide range of innate and adaptive immune responses. A total of 20-50% of acutely HCV-infected individuals permanently control the virus, referred to as 'spontaneous hepatitis C clearance', while the infection progresses to chronic hepatitis C in the majority of cases. Numerous studies have examined host genetic determinants of hepatitis C infection outcome and revealed the influence of genetic polymorphisms of human leukocyte antigens, killer immunoglobulin-like receptors, chemokines, interleukins and interferon-stimulated genes on spontaneous hepatitis C clearance. However, most genetic associations were not confirmed in independent cohorts, revealed opposing results in diverse populations or were limited by varying definitions of hepatitis C outcomes or small sample size. Coordinated efforts are needed in the search for key genetic determinants of spontaneous hepatitis C clearance that include well-conducted candidate genetic and genome-wide association studies, direct sequencing and follow-up functional studies.

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OBJECTIVE: This study developed percentile curves for anthropometric (waist circumference) and cardiovascular (lipid profile) risk factors for US children and adolescents. STUDY DESIGN: A representative sample of US children and adolescents from the National Health and Nutrition Examination Survey from 1988 to 1994 (NHANES III) and the current national series (NHANES 1999-2006) were combined. Percentile curves were constructed, nationally weighted, and smoothed using the Lambda, Mu, and Sigma method. The percentile curves included age- and sex-specific percentile values that correspond with and transition into the adult abnormal cut-off values for each of these anthropometric and cardiovascular components. To increase the sample size, a second series of percentile curves was also created from the combination of the 2 NHANES databases, along with cross-sectional data from the Bogalusa Heart Study, the Muscatine Study, the Fels Longitudinal Study and the Princeton Lipid Research Clinics Study. RESULTS: These analyses resulted in a series of growth curves for waist circumference, total cholesterol, LDL cholesterol, triglycerides, and HDL cholesterol from a combination of pediatric data sets. The cut-off for abnormal waist circumference in adult males (102 cm) was equivalent to the 94(th) percentile line in 18-year-olds, and the cut-off in adult females (88 cm) was equivalent to the 84(th) percentile line in 18-year-olds. Triglycerides were found to have a bimodal pattern among females, with an initial peak at age 11 and a second at age 20; the curve for males increased steadily with age. The HDL curve for females was relatively flat, but the male curve declined starting at age 9 years. Similar curves for total and LDL cholesterol were constructed for both males and females. When data from the additional child studies were added to the national data, there was little difference in their patterns or rates of change from year to year. CONCLUSIONS: These curves represent waist and lipid percentiles for US children and adolescents, with identification of values that transition to adult abnormalities. They could be used conditionally for both epidemiological and possibly clinical applications, although they need to be validated against longitudinal data.

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Monte Carlo simulation was used to evaluate properties of a simple Bayesian MCMC analysis of the random effects model for single group Cormack-Jolly-Seber capture-recapture data. The MCMC method is applied to the model via a logit link, so parameters p, S are on a logit scale, where logit(S) is assumed to have, and is generated from, a normal distribution with mean μ and variance σ2 . Marginal prior distributions on logit(p) and μ were independent normal with mean zero and standard deviation 1.75 for logit(p) and 100 for μ ; hence minimally informative. Marginal prior distribution on σ2 was placed on τ2=1/σ2 as a gamma distribution with α=β=0.001 . The study design has 432 points spread over 5 factors: occasions (t) , new releases per occasion (u), p, μ , and σ . At each design point 100 independent trials were completed (hence 43,200 trials in total), each with sample size n=10,000 from the parameter posterior distribution. At 128 of these design points comparisons are made to previously reported results from a method of moments procedure. We looked at properties of point and interval inference on μ , and σ based on the posterior mean, median, and mode and equal-tailed 95% credibility interval. Bayesian inference did very well for the parameter μ , but under the conditions used here, MCMC inference performance for σ was mixed: poor for sparse data (i.e., only 7 occasions) or σ=0 , but good when there were sufficient data and not small σ .

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BACKGROUND The medial forebrain bundle (MFB) is a key structure of the reward system and connects the ventral tegmental area (VTA) with the nucleus accumbens (NAcc), the medial and lateral orbitofrontal cortex (mOFC, lOFC) and the dorsolateral prefrontal cortex (dlPFC). Previous diffusion tensor imaging (DTI) studies in major depressive disorder point to white matter alterations of regions which may be incorporated in the MFB. Therefore, it was the aim of our study to probe white matter integrity of the MFB using a DTI-based probabilistic fibre tracking approach. METHODS 22 patients with major depressive disorder (MDD) (12 melancholic-MDD patients, 10 non-melancholic-MDD patients) and 21 healthy controls underwent DTI scans. We used a bilateral probabilistic fibre tracking approach to extract pathways between the VTA and NACC, mOFC, lOFC, dlPFC respectively. Mean fractional anisotropy (FA) values were used to compare structural connectivity between groups. RESULTS Mean-FA did not differ between healthy controls and all MDD patients. Compared to healthy controls melancholic MDD-patients had reduced mean-FA in right VTA-lOFC and VTA-dlPFC connections. Furthermore, melancholic-MDD patients had lower mean-FA than non-melancholic MDD-patients in the right VTA-lOFC connection. Mean-FA of these pathways correlated negatively with depression scale rating scores. LIMITATIONS Due to the small sample size and heterogeneous age group comparisons between melancholic and non-melancholic MDD-patients should be regarded as preliminary. CONCLUSIONS Our results suggest that the melancholic subtype of MDD is characterized by white matter microstructure alterations of the MFB. White matter microstructure is associated with both depression severity and anhedonia.

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SUMMARY Split-mouth designs first appeared in dental clinical trials in the late sixties. The main advantage of this study design is its efficiency in terms of sample size as the patients act as their own controls. Cited disadvantages relate to carry-across effects, contamination or spilling of the effects of one intervention to another, period effects if the interventions are delivered at different time periods, difficulty in finding similar comparison sites within patients and the requirement for more complex data analysis. Although some additional thought is required when utilizing a split-mouth design, the efficiency of this design is attractive, particularly in orthodontic clinical studies where carry-across, period effects and dissimilarity between intervention sites does not pose a problem. Selection of the appropriate research design, intervention protocol and statistical method accounting for both the reduced variability and potential clustering effects within patients should be considered for the trial results to be valid.

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The purpose of this study was to analyze the width and height of edentulous sites in the posterior maxilla using cone beam computed tomography (CBCT) images from patients referred for implant therapy. A total of 122 CBCT scans were included in the analysis, resulting in a sample size of 252 edentulous sites. The orofacial crest width was measured in coronal slices, perpendicular to the alveolar ridge. The bone height was analyzed in the respective sagittal slices. Additionally, the following secondary outcome parameters were evaluated: the morphology of the sinus floor, the presence of septa in the maxillary sinus, and the thickness of the sinus membrane. The mean crest width for all analyzed sites was 8.28 mm, and the mean bone height was 7.22 mm. The percentage of patients with a crest width of less than 6 mm was 27% in premolar sites and 7.8% in molar sites. The bone height decreased from premolar to molar areas, with a high percentage of first and second molar sites exhibiting a bone height of less than 5 mm (54.12% and 44.64%, respectively). Regarding the morphology of the sinus floor, 53% of the edentulous sites exhibited a flat configuration. A septum was present in 67 edentulous sites (26.59%). Analysis of the sinus membrane revealed 88 sites (34.9%) with increased mucosal thickness (> 2 mm). For the crest width, the location of the edentulous site and the morphology of the sinus floor were both statistically significant variables. For the crest width and mean bone height, the location of the edentulous site and the morphology of the sinus floor were both statistically significant variables. The study confirmed that a high percentage of edentulous sites in the posterior maxilla do require sinus floor elevation to allow the placement of dental implants. Therefore, a detailed three-dimensional radiograph using CBCT is indicated in most patients for proper treatment planning.

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BACKGROUND Previous meta-analyses comparing the efficacy of psychotherapeutic interventions for depression were clouded by a limited number of within-study treatment comparisons. This study used network meta-analysis, a novel methodological approach that integrates direct and indirect evidence from randomised controlled studies, to re-examine the comparative efficacy of seven psychotherapeutic interventions for adult depression. METHODS AND FINDINGS We conducted systematic literature searches in PubMed, PsycINFO, and Embase up to November 2012, and identified additional studies through earlier meta-analyses and the references of included studies. We identified 198 studies, including 15,118 adult patients with depression, and coded moderator variables. Each of the seven psychotherapeutic interventions was superior to a waitlist control condition with moderate to large effects (range d = -0.62 to d = -0.92). Relative effects of different psychotherapeutic interventions on depressive symptoms were absent to small (range d = 0.01 to d = -0.30). Interpersonal therapy was significantly more effective than supportive therapy (d = -0.30, 95% credibility interval [CrI] [-0.54 to -0.05]). Moderator analysis showed that patient characteristics had no influence on treatment effects, but identified aspects of study quality and sample size as effect modifiers. Smaller effects were found in studies of at least moderate (Δd = 0.29 [-0.01 to 0.58]; p = 0.063) and large size (Δd = 0.33 [0.08 to 0.61]; p = 0.012) and those that had adequate outcome assessment (Δd = 0.38 [-0.06 to 0.87]; p = 0.100). Stepwise restriction of analyses by sample size showed robust effects for cognitive-behavioural therapy, interpersonal therapy, and problem-solving therapy (all d>0.46) compared to waitlist. Empirical evidence from large studies was unavailable or limited for other psychotherapeutic interventions. CONCLUSIONS Overall our results are consistent with the notion that different psychotherapeutic interventions for depression have comparable benefits. However, the robustness of the evidence varies considerably between different psychotherapeutic treatments.

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Responses of many real-world problems can only be evaluated perturbed by noise. In order to make an efficient optimization of these problems possible, intelligent optimization strategies successfully coping with noisy evaluations are required. In this article, a comprehensive review of existing kriging-based methods for the optimization of noisy functions is provided. In summary, ten methods for choosing the sequential samples are described using a unified formalism. They are compared on analytical benchmark problems, whereby the usual assumption of homoscedastic Gaussian noise made in the underlying models is meet. Different problem configurations (noise level, maximum number of observations, initial number of observations) and setups (covariance functions, budget, initial sample size) are considered. It is found that the choices of the initial sample size and the covariance function are not critical. The choice of the method, however, can result in significant differences in the performance. In particular, the three most intuitive criteria are found as poor alternatives. Although no criterion is found consistently more efficient than the others, two specialized methods appear more robust on average.

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ABSTRACT: Fourier transform infrared spectroscopy (FTIRS) can provide detailed information on organic and minerogenic constituents of sediment records. Based on a large number of sediment samples of varying age (0�340 000 yrs) and from very diverse lake settings in Antarctica, Argentina, Canada, Macedonia/Albania, Siberia, and Sweden, we have developed universally applicable calibration models for the quantitative determination of biogenic silica (BSi; n = 816), total inorganic carbon (TIC; n = 879), and total organic carbon (TOC; n = 3164) using FTIRS. These models are based on the differential absorbance of infrared radiation at specific wavelengths with varying concentrations of individual parameters, due to molecular vibrations associated with each parameter. The calibration models have low prediction errors and the predicted values are highly correlated with conventionally measured values (R = 0.94�0.99). Robustness tests indicate the accuracy of the newly developed FTIRS calibration models is similar to that of conventional geochemical analyses. Consequently FTIRS offers a useful and rapid alternative to conventional analyses for the quantitative determination of BSi, TIC, and TOC. The rapidity, cost-effectiveness, and small sample size required enables FTIRS determination of geochemical properties to be undertaken at higher resolutions than would otherwise be possible with the same resource allocation, thus providing crucial sedimentological information for climatic and environmental reconstructions.