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PubMedDate not supplied

Psychometric assessment of the Jalowiec Coping Scale.

The Jalowiec Coping Scale consists of 40 coping behaviors culled from a comprehensive literature review, which are rated on a 1- to 5-point scale to indicate degree of use. Twenty judges classified the items to permit analysis of the coping behaviors according to a problem-oriented/affective-oriented dichotomy; 15 problem and 25 affective items resulted. Overall agreement by the judges was 85%, with greater consensus on problem items. Evaluation of stability using a two-week retest interval (N = 28) yielded significant rhos of .79 for total coping scores, .85 for problem, and .86 for affective. With a one-month interval (N = 30) coefficients were .78, .84, and .83, respectively. Alpha reliability coefficients of .86 (N = 141) and .85 (N = 150) supported instrument homogeneity. Content validity is substantiated by the systematic manner of tool development, by the large number of items used, and by the inclusion of diverse coping behaviors. Factor analysis (N = 141) was used to investigate construct validity. A two-factor solution to evaluate the validity of the dichotomous classification showed that 80% of the problem items loaded on Factor I, but only 56% of the affective items loaded on Factor II. To examine this multidimensional aspect, several other factor solutions were explored. Ultimately, the four-factor solution provided the most intelligible conceptual pattern with the least loss of information. Conceptual composition of these factors is discussed, and several tentative labels for each factor are suggested.

Adaptation, Psychological↗
PubMed1992

Accuracy and precision of the corneal analysis system and the topographic modeling system.

Two computer-assisted topographic analysis systems were evaluated with calibrated spherical surfaces and normal human corneas. The Topographic Modeling System-1 (TMS-1) was found to be statistically more accurate in determining the power of calibrated spheres near the apex and at 1 mm from the apex than the Corneal Analysis System (CAS). The CAS, however, was statistically more accurate at 3 mm from the apex with each calibrated sphere. The small differences in accuracy between the two instruments, however, are unlikely to be of clinical significance. The topographic patterns on color-coded maps from 22 normal corneas of 11 subjects were similar with the two instruments. Simulated keratometry values with the CAS more accurately identified the keratometer-determined major cylinder axis compared with the TMS-1. Conversely, the TMS-1 was more accurate than the CAS at determining the level of corneal astigmatism.

Astigmatism↗
PubMed2006

Microarray analysis of gene expression: considerations in data mining and statistical treatment.

DNA microarray represents a powerful tool in biomedical discoveries. Harnessing the potential of this technology depends on the development and appropriate use of data mining and statistical tools. Significant current advances have made microarray data mining more versatile. Researchers are no longer limited to default choices that generate suboptimal results. Conflicting results in repeated experiments can be resolved through attention to the statistical details. In the current dynamic environment, there are many choices and potential pitfalls for researchers who intend to incorporate microarrays as a research tool. This review is intended to provide a simple framework to understand the choices and identify the pitfalls. Specifically, this review article discusses the choice of microarray platform, preprocessing raw data, differential expression and validation, clustering, annotation and functional characterization of genes, and pathway construction in light of emergent concepts and tools.

Cluster Analysis↗
PubMed1995

The effect of desmopressin on reducing blood loss in cardiac surgery--a meta-analysis of double-blind, placebo-controlled trials.

The effect of desmopressin (DDAVP) on reducing postoperative blood loss after cardiac surgery has been studied in several randomized clinical trials with conflicting outcomes. Since most trials had insufficient statistical power to detect true differences in blood loss, we performed a meta-analysis of data from relevant studies. Seventeen randomized, double-blind, placebo-controlled trials were analyzed, which included 1171 patients undergoing cardiac surgery for various indications; 579 of them were treated with desmopressin and 592 with placebo. Efficacy parameters were blood loss volumes and transfusion requirements. Desmopressin significantly reduced postoperative blood loss by 9%, but had no statistically significant effect on transfusion requirements. A subanalysis revealed that desmopressin had no protective effects in trials in which the mean blood loss in placebo-treated patients fell in the lower and middle thirds of distribution of blood losses (687-1108 ml/24 h). In contrast, in trials in which the mean blood loss in placebo-treated patients fell in the upper third of distribution (> 1109 ml/24 h), desmopressin significantly decreased postoperative blood loss by 34%. Insufficient data were available to perform a sub-analysis on transfusion requirements. Therefore, desmopressin significantly reduces blood loss only in cardiac operations which induce excessive blood loss. Further studies are called to validate the results of this meta-analysis and to identify predictors of excessive blood loss after cardiac surgery.

Adult↗
PubMed1998

Mapping voxel-based statistical power on parametric images.

Using a classic technique based on the noncentral F-distribution method for computing statistical power, we developed a general approach to the estimation of voxel-based power in functional brain image data analysis. We applied this method to PET data from a large sample (N = 40) of subjects performing the Wisconsin Card Sorting (WCST) paradigm analyzed with SPM95, produced statistical power maps for a range of samples sizes and smoothing filter widths, and examined the effects of sample size and image smoothing on the expected reliability of activation findings. At an uncorrected alpha of 0.01, a fixed filter size of 10 mm3, and a range of power thresholds, maps revealed that the power to reject the null hypothesis in brain regions implicated in the task at Ns of 5 and 10 may not be sufficient to ensure reliable replication of significant findings and so should be interpreted with caution. At sample sizes approaching 20 subjects, sufficient power was found in the right dorsolateral prefrontal cortex (BA 46/9), right and left inferior parietal lobule (BA 40), and left inferior temporal lobe (BA 37), comprising the cortical network typically observed during the WCST. Filter size needed to maximize power varied widely, but systematically, across the brain, tending to follow known neuroanatomical landmarks. Statistical power considerations in brain imaging studies are critical for controlling the rate of false negatives and assuring reliable detection of cognitive activation. The variation of filter size for maximizing power across the brain suggests that the underlying neuroanatomy of functional units is an important consideration in the a priori selection of filter size.

Algorithms↗
PubMed1998

Detecting linkage disequilibrium between a polymorphic marker locus and a trait locus in natural populations.

A novel statistical model was developed to test for linkage disequilibrium between a polymorphic genetic marker locus and a locus underlying a quantitative trait (QTL) in natural populations using principles of analysis of variance of unbalanced data and analysis of regression involving data of non-normal distribution. Powers of these statistical tests are formulated as functions of census population size, allelic frequencies at the marker locus and the trait locus, additive and dominance effects at the QTL as well as the coefficient of linkage disequilibrium. Theoretical predictions of the power are validated by extensive Monte Carlo simulations. Among all these factors examined, the amount of the disequilibrium and the size of effect of the QTL are of most importance in determining the power, and the dominance and the allele frequencies at the two loci have substantial effects on the power. Numerical analyses based upon the theoretical calculations and simulation studies favour use of regression of the number of marker alleles on the trait phenotypes as a measure of detection of linkage disequilibrium. Theoretical analysis is also performed to investigate robustness of the formula for predicting the variance of the regression coefficient, which requires normality of the regression variables, whereas normality may not be strictly warranted.

Alleles↗
PubMed2005

Increased power of microarray analysis by use of an algorithm based on a multivariate procedure.

MOTIVATION: The power of microarray analyses to detect differential gene expression strongly depends on the statistical and bioinformatical approaches used for data analysis. Moreover, the simultaneous testing of tens of thousands of genes for differential expression raises the 'multiple testing problem', increasing the probability of obtaining false positive test results. To achieve more reliable results, it is, therefore, necessary to apply adjustment procedures to restrict the family-wise type I error rate (FWE) or the false discovery rate. However, for the biologist the statistical power of such procedures often remains abstract, unless validated by an alternative experimental approach. RESULTS: In the present study, we discuss a multiplicity adjustment procedure applied to classical univariate as well as to recently proposed multivariate gene-expression scores. All procedures strictly control the FWE. We demonstrate that the use of multivariate scores leads to a more efficient identification of differentially expressed genes than the widely used MAS5 approach provided by the Affymetrix software tools (Affymetrix Microarray Suite 5 or GeneChip Operating Software). The practical importance of this finding is successfully validated using real time quantitative PCR and data from spike-in experiments. AVAILABILITY: The R-code of the statistical routines can be obtained from the corresponding author. CONTACT: Schuster@imise.uni-leipzig.de

Algorithms↗
PubMed2000

Detecting failed WBC-reduction processes: a quality assurance program introduced in a blood center.

BACKGROUND: Pragmatic yet statistically valid quality assurance (QA) programs are necessary so that blood centers can select, validate, and monitor their WBC-reduction processes. A QA system for WBC-reduction processes based on the practical application of statistical theory within a large blood center was developed. The system identifies parameters for procedure and component evaluation and provides sample size and formatting suggestions. STUDY DESIGN AND METHODS: Analyses of both procedure and component performance were undertaken during the purchase, validation, and control of filtration and apheresis WBC-reduction processes at Blood Centers of the Pacific from 1997 through 1999. QA analysis was categorized on the basis of whether the process was new to the organization or was a modification of a previously validated system. The numbers of samples necessary to consistently detect failure in platelet yield, unit volume, pH, and WBC count was statistically determined by parametric and nonparametric techniques. RESULTS: Parametric analysis (power analysis) of the mean +/- SD of smaller numbers of samples was highly sensitive to shifted distributions, but only if the shift was normally distributed. Nonparametric analysis, necessary when the nature of the underlying distribution is unknown, suggested a minimal sample of 40 was required to achieve high confidence that significant bimodal failure (a secondary population with WBCs 5% above the cutoff) would be detected. CONCLUSION: A QA system, developed for the evaluation of new or revised WBC-reduction processes, was based on statistical analysis of normally and non-normally distributed process failure. The number of samples was determined that allowed the achievement of confidence and tolerance levels considered appropriate within the blood center. Suggestions for outlier evaluation and a format for performance documentation have also been developed. To better define blood center quality goals, further research is necessary on donor and component biologic variability and the most significant modes of WBC-reduction process failure.

Blood Banks↗
PubMedDate not supplied

The influence of outpatient comprehensive geriatric assessment on survival: a meta-analysis.

Although outpatient Comprehensive Geriatric Assessment (CGA) has shown certain benefits in functional status and quality of life by many randomized controlled trials, no survival benefit has been reported. We hypothesized that the lack of survival benefit may be due to insufficient power of individual trials. In order to assess the influence of outpatient CGA on survival of older persons, we performed a meta-analysis of all randomized controlled trials of outpatient CGA. Nine studies consisting of 3750 subjects fulfilled the predetermined eligible criteria and were included in the meta-analysis. Combined mortality risk ratio with outpatient CGA intervention compared to usual care group was 0.95 (95% confidence interval, CI 0.82-1.12, P = 0.62). Treatment effects were homogeneous across the trials. This meta-analysis did not demonstrate survival benefit for outpatient CGA. Inadequate statistical power is unlikely to explain the results. Future researches of outpatient CGA should focus on coordinated and standardized measurement of outcomes related to functional status, institutionalization rate, and quality of life.

Aged↗
PubMed1986

Estimation and analysis of the concentration-response surfaces associated with multiple-agent combinations.

Chinese hamster cells (V79) were treated with ethylnitrosourea (ENU) and cis-diamminedichloroplatinum(II) (DDP) alone and in combination. Sister chromatid exchanges (SCEs) were quantified as measures of genotoxicity of the two agents. The combination experiment employed a factorial design in which cells were treated, in various concentration combinations, with both agents simultaneously. Response surface methodology, using a polynomial model based on a negative binomial distribution of SCE events, was employed for analysis of the interactions of the two genotoxic agents. The negative binomial distribution, a generalization of the Poisson distribution, is required since SCEs are discrete variables which, under the conditions of these experiments, have a distribution which exhibits extra-Poisson variability. The model of the ENU/DDP combinations indicated an increasingly less-than-additive effect resulting from increasing concentrations of each agent in the combination. The analysis of these experiments demonstrates the usefulness of a powerful statistical procedure for evaluating the biological effects resulting from exposure to multiple cytotoxic agents. The methodology can be used with many other types of endpoints and is not limited by the number of treatment agents.

Cells, Cultured↗
PubMed2025

Network Interactions of Circulating FGF23, HRG-HMGB1, and Cardiac Disease in CKD.

KEY POINTS: Multitrait analysis of genome-wide association study boosts the statistical power to identify novel genetic traits for fibroblast growth factor 23. A functional genomics approach aided network discovery to identify histidine-rich glycoprotein (HRG) and high-mobility group protein box 1 (HMGB1) as key regulators of cardiac disease in CKD. Integration of clinical and genetic data enhances the discovery power and is crucial for understanding the genetic underpinnings of mineral bone disorder related to CKD. BACKGROUND: Genome-wide association studies (GWAS) have identified numerous genetic loci associated with mineral metabolism markers but have exclusively focused on single-trait analysis. In this study, we performed a multitrait analysis of GWAS (MTAG) of mineral metabolism, exploring overlapping genetic architecture between traits to identify novel genetic associations for fibroblast growth factor 23 (FGF23). METHODS: We applied MTAG to variants common to GWAS of five genetically correlated mineral metabolism markers in participants of European ancestry. We integrated UK Biobank GWAS for blood levels for phosphate, 25-hydroxyvitamin D, and calcium (n=366,484) and Cohorts for Heart and Aging Research in Genetic Epidemiology GWAS for parathyroid hormone (n=29,155) and FGF23 (n=13,716). We then used supervised and unsupervised deep machine learning to identify novel associations between genetic traits and FGF23. RESULTS: MTAG increased the effective sample size for mineral metabolism markers to n=50,325 for FGF23. After clumping, MTAG identified independent genome-wide significant single-nucleotide polymorphisms for all traits, including 62 loci for FGF23. Many of these loci have not been previously reported in single-trait analyses. Through a functional genomics approach, we identified histidine-rich glycoprotein (HRG) and high-mobility group box 1 (HMGB1) as master regulators of downstream canonical pathways associated with circulating FGF23, and both genes were highly enriched in hypertrophied cardiac tissue of deceased hemodialysis patients. In addition, we found that DNMT3A was associated with uremic toxin, 8-hydroxy-2-deoxyguanosine, a biomarker of DNA damage. In silico gene perturbation analysis revealed that DNMT3A is protective in patients with heart failure caused by hypertrophied or dilated cardiomyopathy. CONCLUSIONS: Our findings highlight the importance of MTAG analysis of mineral metabolism markers to boost the number of genome-wide significant loci for FGF23 to identify novel genetic traits. Functional genomics revealed novel networks that inform unique cellular functions and identified HRG and HMGB1 as key master regulators of FGF23 and cardiovascular disease in CKD.

bones, stones, and mineral metabolism↗
PubMed2003

Spectral analysis of all-night human sleep EEG in narcoleptic patients and normal subjects.

To investigate the pathophysiology of narcoleptic patients' sleep in detail, we analysed and compared the whole-night polysomnograms of narcoleptic patients and normal human subjects. Eight drug-naive narcoleptic patients and eight age-matched normal volunteers underwent polysomnography (PSG) on two consecutive nights. In addition to conventional visual scoring of the polysomnograms, rapid eye movement (REM)-density and electroencephalograph (EEG) power spectra analyses were also performed. Sleep onset REM periods and fragmented nocturnal sleep were observed as expected in our narcoleptic patients. In the narcoleptic patients, REM period duration across the night did not show the significant increasing trend that is usually observed in normal subjects. In all narcoleptic patient REM periods, eye movement densities were significantly increased. The power spectra of narcoleptic REM sleep significantly increased between 0.3 and 0.9 Hz and decreased between 1.0 and 5.4 Hz. Further analysis revealed that non-rapid eye movement (NREM) period duration and the declining trend of delta power density in the narcoleptic patients were not significantly different from the normal subjects. Compared with normal subjects, the power spectra of narcoleptic NREM sleep increased in the 1.0-1.4 Hz and 11.0-11.9 Hz frequency bands, and decreased in a 24.0-26.9 Hz frequency band. Thus, increased EEG delta and decreased beta power densities were commonly observed in both the NREM and REM sleep of the narcoleptic patients, although the decrease in beta power during REM sleep was not statistically significant. Our visual analysis revealed fragmented nocturnal sleep and increased phasic REM components in the narcoleptic patients, which suggest the disturbance of sleep maintenance mechanism(s) and excessive effects of the mechanism(s) underlying eye movement activities during REM sleep in narcolepsy. Spectral analysis revealed significant increases in delta components and decreases in beta components, which suggest decreased activity in central arousal mechanisms. These characteristics lead us to hypothesize that two countervailing mechanisms underlie narcoleptic sleep pathology.

Adult↗
PubMedDate not supplied

Large trials vs meta-analysis of smaller trials: how do their results compare?

OBJECTIVE: To evaluate the results of large clinical trials vs the pooled results of smaller trials. DATA IDENTIFICATION: Meta-analyses with at least 1 "large" study were identified from the Cochrane Pregnancy and Childbirth Database and from MEDLINE (1966-1995). STUDY SELECTION: We used a sample size approach to select 79 meta-analyses with at least 1 large study of 1000 or more patients. We used a statistical power approach to select 61 meta-analyses with at least 1 large study based on statistical power considerations. DATA EXTRACTION: The outcome of interest for each meta-analysis was the primary one stated in the original publication or, when not clearly specified, was decided on clinically. DATA SYNTHESIS: By random effects calculations, we found agreement between large and smaller trials in 90% of the meta-analyses selected by the sample size approach and in 82% of the meta-analyses selected by the statistical power approach. Twice as many disagreements appeared when the variability among large studies and among smaller studies was not considered (ie, fixed effects calculations). Of the 15 disagreements between results of large and smaller trials using the random effects model, plausible explanations were identified in 10 meta-analyses: 5 with differences in the control rate of events between large and smaller trials, 4 with specific protocol or study differences, and 1 with potential publication bias. Two other disagreements were not clinically important, and tentative reasons could be identified for 2 of the remaining 3 disagreements. CONCLUSIONS: Results of smaller studies are usually compatible with the results of large studies, but discrepancies do occur even when the diversity among both large studies and smaller studies is considered. Clinically important differences without a potential explanation are extremely uncommon. Future research should further examine sources of heterogeneity between the results of large and smaller trials.

Bias↗
PubMed1994

Statistical analysis of topographic maps of short-latency somatosensory evoked potentials in normal and parkinsonian subjects.

This work had the following objectives: i) to integrate temporal analysis (N30 peak) with power-spectrum topographic mapping of short-latency somatosensory evoked potentials (SEP's) recorded in parkinsonian and normal control subjects; and ii) to analyze with a new statistical approach the between-group topographical differences in both the time and frequency domains. The principal aim was to better determine the topography of the scalp frontal areas where the amplitude of the N30 wave was previously found to be significantly reduced in parkinsonians. The statistical procedure was based on the combined use of descriptive data analysis (DDA) and multivariate analysis. In the context of DDA, an improved version of significance probability mapping (SPM) was used by which it is possible to evaluate homo- and nonhomoscedastic data with parametric tests. The statistical evaluation of between-group differences was performed with the multivariate Hotelling's T2 test and the associated post hoc test. With this statistical procedure, it was possible to determine that the between-group statistical differences in both the temporal and power spectrum distributions were localized only in midline and contiguous contralateral frontal areas of the scalp.

Brain Mapping↗
PubMed2005

Determination of the origin of unknown irradiated nuclear fuel.

An isotopic fingerprinting method is presented to determine the origin of unknown nuclear material with forensic importance. Spent nuclear fuel of known origin has been considered as the 'unknown' nuclear material in order to demonstrate the method and verify its prediction capabilities. The method compares, using factor analysis, the measured U, Pu isotopic compositions of the 'unknown' material with U, Pu isotopic compositions simulating well known spent fuels from a range of commercial nuclear power stations. Then, the 'unknown' fuel has the same origin as the commercial fuel with which it exhibits the highest similarity in U, Pu compositions.

Factor Analysis, Statistical↗
PubMed1990

Statistical power of psychological research: what have we gained in 20 years?

Power was calculated for 6,155 statistical tests in 221 journal articles published in the 1982 volumes of the Journal of Abnormal Psychology, Journal of Consulting and Clinical Psychology, and Journal of Personality and Social Psychology. Power to detect small, medium, and large effects was .17, .57, and .83, respectively. 20 years after Cohen (1962) conducted the first power survey, the power of psychological research is still low. The implications of these results concerning the proliferation of Type I errors in the published literature, the failure of replication studies, and the interpretation of null (negative) results are emphasized. An example is given of the use of power analysis to help interpret null results by setting probable upper bounds on the magnitudes of effects. Limitations of statistical power analyses, suggestions for future research, sources of computational information, and recommendations for improving power are discussed.

Humans↗
PubMed2026

PYRAMA: an open-source tool for advanced meta-analysis of genome wide association studies.

MOTIVATION: Genome-wide association study (GWAS) meta-analysis tools are essential for integrating summary statistics across multiple cohorts, thereby increasing statistical power and validating genetic associations. Widely cited tools, such as METAL, PLINK, and GWAMA, have facilitated numerous significant discoveries in the field of GWAS. Nevertheless, these tools offer a limited set of meta-analysis methods and typically require users to have prior experience with command-line tools to be executed. RESULTS: We present here PYRAMA, an open-source tool which is designed for meta-analysis of genome wide association studies. This work introduces an easy-to-use software package that includes several meta-analysis methods that are absent in similar software packages. PYRAMA is faster compared to other tools, supports robust methods for analysis and meta-analysis, fixed-effects, random-effects and Bayesian meta-analysis and it is currently the only tool that supports meta-analysis with imputation of summary statistics. It is available both as a standalone tool and as a freely available web server. AVAILABILITY AND IMPLEMENTATION: https://github.com/pbagos/PYRAMA, https://doi.org/10.5281/zenodo.17830449.

Genome-Wide Association Study↗
PubMedDate not supplied

[Taxonomic value of the characterization of Pseudomonas by the analysis of volatile fatty acids produced in culture].

Gas liquid-chromatography was used in order to characterize the volatile fatty acids produced in culture supernatants by 632 Pseudomonas strains. Statistical analysis of these results allowed testing of the discriminatory power of this analytical methodology (factor analysis) to point out the presence of subgroups (clustering according to the variance) and to show the relationship between species and subspecies (three-dimensional plot). Fourteen Pseudomonas species could be accurately characterized by this methodology; the classification of Pseudomonas build up, on the basis of qualitative and quantitative aspects of their volatile fatty acids production, agrees with the current classification based on rRNA/DNA homology complexes.

Chromatography, Gas↗