Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Statistical power analysis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources
PubMed2003

Rural interdisciplinary mental health team building via satellite: a demonstration project.

This paper reports on the results of a demonstration project that examined the role of telehealth/telemedicine (hereafter referred to as telehealth) in providing interdisciplinary mental health training and support to health professionals in a rural region of Atlantic Canada. Special emphasis was placed on addressing the question of how training might affect interdisciplinary collaboration among the rural health professionals. Five urban mental health professionals from three disciplines provided training and support via video-satellite and internet, print and video resources to 34 rural health and community professionals. In order to assess the rural community's needs and the impact of the interventions, questionnaires were administered and on-site interviews were conducted before and after the project. Throughout the project, field notes were recorded and satisfaction ratings were obtained. Satisfaction with the video-satellite presentations was high and stable, with the exception of one session when signal quality was very poor. Rural participants were most satisfied with opportunities for interaction and least satisfied with the variable quality of the video transmission signal. High staff turnover among rural professionals resulted in insufficient power to permit statistical analysis. Positive reports of the project impact included expanded knowledge and heightened sensitivity to mental health issues, increased cross-disciplinary connections, and greater cohesion among professionals. The results suggest that, with some refinements, telehealth technology can be used to facilitate mental health training and promote interdisciplinary collaboration among professionals in a rural setting.

Counseling↗
PubMed2003

Sample size needed to detect gene-gene interactions using association designs.

It is likely that many complex diseases result from interactions among several genes, as well as environmental factors. The presence of such interactions poses challenges to investigators in identifying susceptibility genes, understanding biologic pathways, and predicting and controlling disease risks. Recently, Gauderman (Am J Epidemiol 2002;155:478-84) reported results from the first systematic analysis of the statistical power needed to detect gene-gene interactions in association studies. However, Gauderman used different statistical models to model disease risks for different study designs, and he assumed a very low disease prevalence to make different models more comparable. In this article, assuming a logistic model for disease risk for different study designs, the authors investigate the power of population-based and family-based association designs to detect gene-gene interactions for common diseases. The results indicate that population-based designs are more powerful than family-based designs for detecting gene-gene interactions when disease prevalence in the study population is moderate.

Genetic Predisposition to Disease↗
PubMed2006

Folate nutrition and prostate cancer incidence in a large cohort of US men.

Folate has important roles in DNA synthesis, repair, and methylation and is inversely associated with the risk of some cancers. The authors examined this association among 65,836 men in the American Cancer Society Cancer Prevention Study II Nutrition Cohort. During 9 years of follow-up, 5,158 men were diagnosed with prostate cancer. Folate intakes were estimated from the questionnaire administered at enrollment in 1992-1993, and Cox proportional hazards models were used to calculate hazard rate ratios adjusted for potential confounders. Neither dietary nor total folate intake was associated with prostate cancer overall. However, higher folate levels were associated with a nonsignificant decreased risk of advanced prostate cancer (multivariate rate ratio=0.78, 95% confidence interval: 0.53, 1.15 for the highest vs. lowest quintiles of dietary folate and rate ratio=0.79, 95% confidence interval: 0.54, 1.17 for the highest vs. lowest quintile of total folate). The association was similar for quintiles 2-5, suggesting that only a small increase in folate intake was needed to alter the risk of advanced prostate cancer. Because the statistical power of the analysis with advanced prostate cancer was limited by the low number of cases, further study is needed to establish this association.

Aged↗
PubMed2000

Inaccuracy of clinical phenotyping parameters for hypertensive nephrosclerosis.

BACKGROUND: Multiple studies suggest that hypertension-induced end-stage renal disease (ESRD) is heritable. Identification of nephropathy susceptibility genes absolutely requires accurate phenotyping, but the clinical hypertensive nephrosclerosis (HN) phenotype is poorly characterized. We hypothesized that many patients with HN as the indicated cause of ESRD on the Health Care Financing Administration (HCFA) 2728 form, fail to satisfy stringent HN phenotyping criteria. METHODS: Since renal biopsy documentation of HN is uncommon, clinical parameters for HN phenotype were applied: family history of hypertension, left ventricular hypertrophy, proteinuria <0.5 g/day, and hypertension preceding renal dysfunction (Schlessinger et al., 1994) or urine protein:creatinine (prot:creat) ratio <2.0 and no evidence of other renal diseases (AASK Trial Group, 1997). RESULTS: ESRD patients (n=607, 73% African American, 25% Caucasian) were enrolled in a study to identify HN susceptibility genes. HN was the most common cause of ESRD according to HCFA 2728 forms (37% prevalence). Phenotyping of randomly selected patients with HN from the total cohort revealed that 4/100 subjects satisfied the Schlessinger criteria, and 28/91 African Americans met AASK criteria for HN. From these figures, the adjusted prevalence of HN was only 1.5-13.5%. Of patients that could not be phenotyped for HN, 14 were misdiagnosed, 14 had urine prot:creat >2.0, and insufficient data were available in the remainder. Four patients underwent renal biopsy, but histology from only one was consistent with HN. If the HN phenotype definitions are revised to exclude 'hypertension preceding renal dysfunction', or proteinuria limits, then 44/100 and 39/91 patients respectively satisfy clinical phenotyping parameters for HN. CONCLUSIONS: (i) We provide the strongest evidence to date that HN is less frequent in an ESRD population than commonly assumed if strict clinical criteria are used; many patients clinically diagnosed with HN may have undetected, treatable renal disease from other causes; (ii) relaxing HN phenotype criteria may erroneously include patients with glomerular diseases and secondary hypertension; (iii) reliance on HCFA 2728 diagnoses will confound identification of HN susceptibility genes; (iv) to attain adequate statistical power for genotype analysis, rigorous HN phenotyping will require screening an extremely large number of patients, which can be reasonably accomplished only in a multi-centre trial design.

Black People↗
PubMed2002

Malignant fibrous histiocytoma of the spermatic cord: a case report.

Malignant fibrous histiocytoma (MFH) of the spermatic cord represents an uncommon location for the most common soft-tissue tumor in adults. MFH of the spermatic cord is such a rare entity that only 28 case reports have been described in the literature to date. The rarity of MFH of the spermatic cord has made diagnosis, staging, and treatment difficult. Solutions to such questions will only be answered as our database continues to expand. Therefore, this case report is presented in hopes of lending statistical power to future analysis of the correct treatment planning, mortality rates, and prognostic indications of a relatively unknown subset of a common disease.

Genital Diseases, Male↗
PubMed1998

The conundrum of the Glasgow Coma Scale in intubated patients: a linear regression prediction of the Glasgow verbal score from the Glasgow eye and motor scores.

BACKGROUND: The Glasgow Coma Scale (GCS), which is the foundation of the Trauma Score, Trauma and Injury Severity Score, and the Acute Physiology and Chronic Health Evaluation scoring systems, requires a verbal response. In some series, up to 50% of injured patients must be excluded from analysis because of lack of a verbal component for the GCS. The present study extends previous work evaluating derivation of the verbal score from the eye and motor components of the GCS. METHODS: Data were obtained from a state trauma registry for 24,565 unintubated patients. The eye and motor scores were used in a previously published regression model to predict the verbal score: Derived Verbal Score = -0.3756 + Motor Score * (0.5713) + Eye Score * (0.4233). The correlation of the actual and derived verbal and GCS scales were assessed. In addition the ability of the actual and derived GCS to predict patient survival in a logistic regression model were analyzed using the PC SAS system for statistical analysis. The predictive power of the actual and the predicted GCS were compared using the area under the receiver operator characteristic curve and Hosmer-Lemeshow goodness-of-fit testing. RESULTS: A total of 24,085 patients were available for analysis. The mean actual verbal score was 4.4 +/- 1.3 versus a predicted verbal score of 4.3 +/- 1.2 (r = 0.90, p = 0.0001). The actual GCS was 13.6 + 3.5 versus a predicted GCS of 13.7 +/- 3.4 (r = 0.97, p = 0.0001). The results of the comparison of the prediction of survival in patients based on the actual GCS and the derived GCS show that the mean actual GCS was 13.5 + 3.5 versus 13.7 + 3.4 in the regression predicted model. The area under the receiver operator characteristic curve for predicting survival of the two values was similar at 0.868 for the actual GCS compared with 0.850 for the predicted GCS. CONCLUSIONS: The previously derived method of calculating the verbal score from the eye and motor scores is an excellent predictor of the actual verbal score. Furthermore, the derived GCS performed better than the actual GCS by several measures. The present study confirms previous work that a very accurate GCS can be derived in the absence of the verbal component.

Glasgow Coma Scale↗
PubMed1998

European Collaborative Project on Affective Disorders: interactions between genetic and psychosocial vulnerability factors.

Despite strong evidence provided by genetic epidemiology of genetic involvement in the aetiology of bipolar and unipolar affective disorders, the exact nature of the predisposing gene(s) is still being investigated through linkage and association studies. The interaction of susceptibility genes and environmental factors in these diseases is also of fundamental importance and requires proper investigation. Interesting theories have recently been proposed examining the possible role of various chromosomal regions, candidate genes and mutations in affective disorders. Reliable multicentre-based methodology is currently being employed to examine these theories, with attention given to statistical analysis and the statistical power of the sample. The present article describes the European Collaborative Project on Affective Disorders (ECPAD) 'Interactions between genetic and psychosocial vulnerability factors', involving 15 European centres. A description is given of the association and family samples collected for the project and also the methodology used to analyse interactions in the gene-psychosocial environment. This material provides a powerful tool in the search for susceptibility genes in affective disorders and takes into account non-genetic aetiological factors.

Adolescent↗
PubMed2005

Prognostic relevance of clinical symptoms in patients with spinal metastases.

UNLABELLED: Medical and surgical advances allow surgical treatment of many patients with spinal metastases. Although emerging surgical techniques facilitate stabilization of the collapsed spine, surgical candidates should be carefully selected. However, the lack of confirmed criteria to determine survival of these patients makes selection for surgery difficult. Clinical symptoms have been considered possible factors associated with prognosis, but their relevance has not been confirmed because of inadequate power for proper statistical analysis. We retrospectively reviewed 165 patients who had surgery for spinal metastases from various cancers. Clinical symptoms including pain, paresis, and walking status were recorded. Multivariate analysis indicated that the histologic type of the primary tumor was the strongest prognostic factor, followed by preoperative paresis and pain. Myeloma, thyroid cancer, renal cell cancer, breast cancer, and prostate cancer had better prognoses than other kinds of cancer. Patients without paresis before surgery had a better prognosis than patients with paresis, and patients with no pain before surgery had a better prognosis than those with pain. Preoperative walking status was not an independent prognostic factor. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series--no, or historical control group). See the Guidelines for Authors for a complete description of levels of evidence.

Evidence-Based Medicine↗
PubMed2025

An Updated Polygenic Index Repository: Expanded Phenotypes, New Cohorts, and Improved Causal Inference.

Polygenic indexes (PGIs) - DNA-based predictors of individual phenotypes - have become essential tools across biomedical and social sciences. We introduce Version 2 of the Polygenic Index Repository, which expands phenotype coverage from 47 to 61, increases the number of participating datasets from 11 to 20, and adopts a more consistent and improved methodology for PGI construction. For 16 phenotypes, we leverage summary statistics from an updated GWAS meta-analysis with greater statistical power compared to the original release, thereby improving the PGI's predictive power. To improve power for family-based analyses, we provide imputed parental PGIs in all datasets with first-degree relatives and offer a framework for interpreting results from analyses that control for parental PGIs. We illustrate the utility of parental PGIs using two applications: (1) comparing PGI associations with and without parental PGI controls for all phenotypes in two Repository datasets with family data, and (2) for BMI and diastolic blood pressure, exploring the contribution of causal versus non-causal components of PGI associations to the imperfect portability of PGIs across subgroups within a genetic ancestry. Collectively, the updates enhance predictive performance, broaden the Repository's scope, and introduce novel resources that reduce confounding bias and improve interpretability.

Journal Article↗
PubMed2002

Evolution of white matter lesions.

A 3-year follow-up of 273 participants (mean age 60 years) of the Austrian Stroke Prevention Study provides first information on the rate, clinical predictors and cognitive consequences of MRI white matter lesions (WML) in elderly individuals without neuropsychiatric disease. Lesion progression was found in 17.9% of individuals over a time period of 3 years. Diastolic blood pressure and early confluent or confluent white matter hyperintensities at baseline were the only significant predictors of white matter hyperintensity progression. Genetic association studies in the setting of the Austrian Stroke Prevention Study provide first evidence for genetic susceptibility factors for progression of WML. We observed associations with the paraoxonase Leu-->Met 54 polymorphism and with the M235T polymorphism of the angiotensinogen gene. Lesion progression had no influence on the course of neuropsychologic test performance over the observational period, but the statistical power of this analysis was low.

Aged↗
PubMed2006

Pediatric neurosurgery.

Randomized controlled trials of neurosurgical procedures involving children have been organized infrequently; as a consequence, the majority of pediatric neurosurgical practice is not supported by class I data. Furthermore, many trials that have been reported suffer from serious methodological shortcomings such as insufficient power and poor statistical analysis. Finally, several trials of neurosurgical techniques that are frequently performed on children have either excluded children from participation or include an insufficient number of children to draw strong conclusions. Despite these shortcomings, pediatric neurosurgery, like all fields in medicine, is gradually moving towards a more stringent evidence-based medicine standard. This chapter will attempt to summarize the recent progress that has been made in this area.

Clinical Trials as Topic↗
PubMed1994

Prognostic factors in lung cancer: tables and comments.

Prognostic factors (PF) have a pivotal role in Clinical Oncology. They are helpful in the selection of treatment, provide insights into the disease process and the therapeutic response, and are fundamental in the design of clinical trials or in the interpretation of data from the literature. The number of possibly useful PFs in lung cancer is large (certainly more than one hundred). This paper attempts to provide a comprehensive listing of PFs and other variables potentially associated with outcome of lung cancer. This is achieved using tables, where studies relevant to each PF are referenced in relationship to their results, statistical power, type of analysis, number of variables incorporated in multivariate tests, and cell type. Tables include the outcome of an extensive retrieval of the literature and indicate visually where much of the evidence resides for the contribution of a variable to prognosis. Each table is briefly discussed and systematically comprises one group of PFs. Among the many pinpointed, the best predictive models still belong to studies based on clinical and routine laboratory data. Recent researches have clarified the role of new PFs (such as the biological factors); others (e.g. quality of life measures, the serum content of acute phase reaction proteins or the pathological evidence of tumour neoangiogenesis) might be recognized as important in the future. Like infinity, the fate of the individual patient will never become a completely measurable entity. However, as the discovery of new PFs proceeds, the assessment of the future prospects for patients is becoming more reliable.

Humans↗
PubMed2002

Assessing the evidence on case management.

BACKGROUND: Evidence on the impact of case management is contradictory. AIMS: To discuss two different systematic reviews (one conducted by the authors and one conducted through the Cochrane collaboration) that came to contradictory conclusions about the impact of case management in mental health services. METHOD: We summarised the findings of the two reviews with respect to case management effectiveness, examined key methodological differences between the two approaches and discuss the impact of these on the validity of the results. RESULTS: The differences in conclusions between the two reviews result from the differences in inclusion criteria, namely non-randomised trials, data from unpublished scales and data from variables with skewed distributions. The theoretical and empirical effects of these are discussed. CONCLUSIONS: Systematic reviewers may face a trade-off between the application of strict criteria for the inclusion of studies and the amount of data available for analysis and hence statistical power. The available research suggests that case management is generally effective.

Case Management↗
PubMed1994

Combination chemotherapy, glucocorticoids, and interferon alfa in the treatment of multiple myeloma: a Southwest Oncology Group study.

PURPOSE: Standard therapy for multiple myeloma consists of cytotoxic chemotherapy plus glucocorticoids. Interferon (IFN) alfa maintenance is reported to prolong chemotherapy-induced remissions and survival. This study evaluates induction chemotherapy, glucocorticoids, and interferon maintenance in myeloma. PATIENTS AND METHODS: Five hundred twenty-two previously untreated myeloma patients were randomized to three chemotherapy regimens with differing glucocorticoid intensities. Patients who achieved remission were randomized to receive IFN or observation until relapse. Patients who failed to respond to chemotherapy received IFN alfa plus dexamethasone (DEX). RESULTS: Five hundred nine patients were eligible for induction chemotherapy. Chemotherapy with higher dose-intensity glucocorticoids yielded higher response rates and improved survival (P = .02 for the three-group comparison; P < .05 for each higher glucocorticoid arm v vincristine, melphalan, cyclophosphamide, and prednisone alternating with vincristine, carmustine [BCNU], doxorubicin, and prednisone [VMCP/VBAP]). One hundred ninety-three patients who achieved remission were randomized to receive IFN alfa 3 MU three times weekly or observation. IFN was not superior to observation for relapse-free (P = .95) or overall survival (P = .39) from start of maintenance. Eighty-eight induction failures received 5 MU of IFN three times weekly plus DEX. Patients who received IFN/DEX had a median survival duration of 48 months from start of IFN/DEX. CONCLUSION: Higher-dose glucocorticoids increases frequency of response to chemotherapy and prolong survival in myeloma. IFN maintenance with the dose schedule used in this trial did not prolong relapse-free or overall survival. We cannot exclude a small effect of IFN, as most individual trials do not have sufficient statistical power. Meta-analysis of randomized trials evaluating IFN maintenance in myeloma might be of value. While IFN appeared ineffective, addition of higher-dose glucocorticoids improved outcome in myeloma.

Adult↗
PubMed1987

General metabolism in head injury.

Seventy-six patients with closed head injuries alone were studied to define the relation between the severity of the head injury and secondary alterations of general metabolism. The effect of metabolic changes on neurological outcome and the importance of nutritional support on nutritional status and neurological outcome were also evaluated. Using a powerful statistical tool, convergence analysis, it was possible to take into consideration the effects of a number of confounding factors that obviously affected general metabolism. Most of the patients were hypermetabolic for prolonged periods. In addition, many did not receive even basal requirements of calories or protein for many days. Despite this, their outcomes were determined by their initial neurological status and the amounts that they were fed, admittedly relatively modest, did not influence their courses. Despite such feedings, their visceral protein levels, which often dropped initially, rose toward normal levels, indicating effective adaptation. Indeed, it could not be shown that these patients developed complications of malnutrition such as infections. However, it will require a sophisticated randomized clinical trial of vigorous intravenous hyperalimentation to determine whether this complex, dangerous, and expensive therapy is helpful for severely head-injured patients.

Craniocerebral Trauma↗
PubMed2002

Child welfare knowledge transmission, practitioner retention, and university-community impact: a study of Title IV-E child welfare training.

This paper describes the implementation of a Title IV-E child welfare training program in Louisiana. A collaborative arrangement between the state child welfare agency and seven state university social work programs provides for student monetary stipends in return for child welfare training and work as public child welfare employees upon graduation. On a test of child welfare knowledge, students in MSW and BSW programs scored higher following child welfare training; BSW student stipend recipients made greater gains than non-recipients when controlling for initial scores. MSW students' results appear to approach significance; they may not be significant due to low power of the statistical analysis. Child welfare agency retention of the stipend student graduates is considered good by the agency.

Adult↗
PubMed2005

Incorporating biological information as a prior in an empirical bayes approach to analyzing microarray data.

Currently the practice of using existing biological knowledge in analyzing high throughput genomic and proteomic data is mainly for the purpose of validations. Here we take a different approach of incorporating biological knowledge into statistical analysis to improve statistical power and efficiency. Specifically, we consider how to fuse biological information into a mixture model to analyze microarray data. In contrast to a standard mixture model where it is assumed that all the genes come from the same (marginal) distribution, including an equal prior probability of having an event, such as having differential expression or being bound by a transcription factor (TF), our proposed mixture model allows the genes in different groups to have different distributions while the grouping of the genes reflects biological information. Using a list of about 800 putative cell cycle-regulated genes as prior biological knowledge, we analyze a genome-wide location data to detect binding sites of TF Fkh1. We find that our proposal improves over the standard approach, resulting in reduced false discovery rates (FDR), and hence it is a useful alternative to the current practice.

Journal Article↗
PubMed2003

Sample size calculation for studies on temporomandibular disorders.

Sample size calculation is a fundamental step for the validity and the usefulness of results from a study. Nevertheless, as demonstrated by some papers in the literature, such calculation is often ignored. Despite the lack of papers on this topic, it is probable that this shortcoming also affects studies on temporomandibular disorders. Therefore, the aim of this paper was to provide some basic rules to calculate the sample size necessary for different types of studies, both longitudinal and transversal, on those pathologies. Some examples of the application of such rules for different types of studies have also been provided, in order to make a full comprehension easier. In fact, the systematic application of those rules is strongly requested for the effective usefulness of results. Furthermore, an analysis of the statistical power of past studies on temporomandibular disorders could be useful to evaluate if our epidemiological and clinical-therapeutic knowledge of temporomandibular disorders is effectively based upon studies conducted with the appropriate sample size.

Clinical Trials as Topic↗