Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Statistical Power”

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 1,369 records · Page 76Linked to original sources
PubMed1999

Four-week nicotine skin patch treatment effects on cognitive performance in Alzheimer's disease.

RATIONALE: Acute nicotine injections have been found to improve attentional performance in patients with Alzheimer's disease (AD), but little is known about chronic nicotine effects. OBJECTIVE: The present study was undertaken to evaluate the clinical and neuropsychological effects of chronic transdermal nicotine in Alzheimer's disease subjects over a 4-week period. METHODS: The double-blind, placebo controlled, cross-over study consisted of two 4-week periods separated by a 2-week washout period. Patients wore the nicotine patch (Nicotrol) for 16 h a day at the following doses: 5 mg/day during week 1, 10 mg/day during weeks 2 and 3 and 5 mg/day during week 4. The eight subjects had mild to moderate AD and were otherwise healthy. RESULTS: Nicotine significantly improved attentional performance as measured by the Conners' continuous performance test (CPT). There was a significant reduction in errors of omission on the CPT which continued throughout the period of chronic nicotine administration. The variability of hit reaction time (reaction time for correct responses) on the CPT was also significantly reduced by chronic nicotine. Nicotine did not improve performance on other tests measuring motor and memory function. CONCLUSIONS: The sustained improvement in attention found in this study with nicotine dermal patches is encouraging. However, the lack of detected effects of nicotine treatment on other cognitive and behavioral domains in this study leaves questions concerning the clinical impact of nicotinic treatment in Alzheimer's disease. The modest size of this study limited statistical power which may have been needed to detect more subtle but clinically significant cognitive effects. Higher doses of nicotine, other nicotinic ligands or combination treatment of nicotine with other therapies may be efficacious for producing broader therapeutic effects.

Administration, Cutaneous↗
PubMed2006

Increasing cognitive load with increasing balance challenge: recipe for catastrophe.

The variety of sometimes contradictory results of studies of the impact of secondary cognitive tasks on postural balance may be attributed to the heterogeneity of balance challenges and tasks deployed and frequent lack of quantitative comparability of tasks. We deployed a wide range of quantitatively graded difficulties of both balance challenge and cognitive tasking to obtain an overview of the spectrum of their interactions in a multi-tasking situation. A differential comparison of the effects of verbally versus spatially loaded tasks, balanced for difficulty, was made and unlike any other study, we contrived to incorporate falls as an experimental variable. In the first study subjects stood in tandem on beams of either 2, 3 and 6 cm or 3, 6 and 8 cm width (according to 'best performance' ability) while performing mental verbal or spatial 'Stroop' tasks. The design was a between groups (sixteen subjects each) comparison (to reduce learning effect) of sway, fall rate and task error, balanced for order. Measurements were taken of centre of pressure, sway velocity at the hip and head displacement. For any beam width there were no within-subject correlations between sway magnitudes and frequency of falls. Spatial task errors increased with balance challenge (hence with magnitude of sway) but verbal performance was maintained independently of balance challenge. The results of the first study provided statistical power estimates for the design of the second focussed experiment which made a within group (twenty four subjects) comparison of the impact of spatial versus verbal tasks on balancing on the hardest beam. The spatial task significantly elevated the incidence of falls whereas the verbal task had no effect on fall rate. The spatial task raised the incidence of falling by 50% (P = 0.0008) in comparison with 'no task'. The verbal task had no effect (P = 0.07). We conclude that sway magnitude is a poor index of multi-task load. Multi-tasking can increase the chance of falling and spatial processing may have a specific impact on balance. The significant elevation of fall frequency during cognitive tasking shows that the 'posture first' principal can be transgressed although the necessary condition for transgression may be that the subject is willing to take risks believing that he can arrest any fall.

Accidental Falls↗
PubMed2001

Bone density measured by dual-energy X-ray absorptiometry in healthy Kuwaiti women.

A preliminary cross-sectional study of 623 healthy Kuwaiti women aged 20-79 years was carried out using dual-energy X-ray absorptiometry (DXA) to establish reference values of bone mineral density (BMD). Measurements were taken at the lumbar spine and proximal femur. The data were compared with normative data taken from Caucasian U.S./North European women over 6 decades of age. Our results showed the expected decline in BMD with age, especially for postmenopausal women. Despite differences in ethnicity, diet, and lifestyle no statistically significant differences in BMD were detected between the Kuwaiti subjects and the Caucasian normative data. Age-matched, clinically well-defined normative data for a given population must be used to diagnose osteoporosis and establish fracture risk. This study represents baseline data for Kuwaiti Arab females: it indicates that their BMD values are close to those of Caucasian females and higher than those reported recently for Lebanese and Saudi females. Further data is being collected to increase the statistical power of the study.

Absorptiometry, Photon↗
PubMed2003

A stone farm: development of a method for simultaneous production of multiple calcium oxalate stones in vitro.

We have previously shown how individual calcium oxalate stones of about 1 cm can be grown in vitro. While this proved a design concept, it was severely limited as an experimental tool because of the time required to undertake comparative studies. Here we describe a development of this system in which six parallel pairs of stone generators are supplied with feed solutions generating a medium that is supersaturated with calcium oxalate. Twelve stones were grown simultaneously in aseptically prepared artificial urine over a period of 32 days from 100 mg to about 250 mg. Flow rates, pH and [Ca(2+)] were stable and reproducible over the course of the experiment. Sodium azide (0.02%) was included in the growth medium of six stones and caused a modest decrease in growth rate from 5.5 to 3.4 mg/day. The experimental design is such that this was readily detectable both visually and statistically ( p<0.001). This multiple stone growing system ("a stone farm") shows improved consistency and illustrates the statistical power of the technique. Azide has only a minor effect on the growth kinetics and can be used as an antibacterial agent in studies involving urinary macromolecules. The technique is suitable for practical and meaningful investigation of calcium oxalate stone formation in vitro.

Calcium Oxalate↗
PubMed2001

Spiral CT scanning technique in the detection of aspiration of LEGO foreign bodies.

BACKGROUND: Radiolucent foreign bodies (FBs) such as plastic objects and toys remain difficult to identify on conventional radiographs of the neck and chest. Children may present with a variety of respiratory complaints, which may or may not be due to a FB. OBJECTIVE: To determine whether radiolucent FBs such as plastic LEGOs and peanuts can be seen in the tracheobronchial tree or esophagus using low-dose spiral CT, and, if visible, to determine the optimal CT imaging technique. MATERIALS AND METHODS: Multiple spiral sequences were performed while varying the CT parameters and the presence and location of FBs in either the trachea or the esophagus first on a neck phantom and then a cadaver. Sequences were rated by three radiologists blinded to the presence of a FB using a single scoring system. RESULTS: The LEGO was well visualized in the trachea by all three readers (both lung and soft-tissue windowing: combined sensitivity 89 %, combined specificity 89 %) and to a lesser extent in the esophagus (combined sensitivity 31 %, combined specificity 100 %). The peanut was not well visualized (combined sensitivity < 35 %). The optimal technique for visualizing the LEGO was 120 kV, 90 mA, 3-mm collimation, 0.75 s/revolution, and 2.0 pitch. This allowed for coverage of the cadaver tracheobronchial tree (approximately 11 cm) in about 18 s. Although statistical power was low for detecting significant differences, all three readers noted higher average confidence ratings with lung windowing among 18 LEGO-in-trachea scans. CONCLUSION: Rapid, low-dose spiral CT may be used to visualize LEGO FBs in the airway or esophagus. Peanuts were not well visualized.

Arachis↗
PubMed2006

IBZM tool: a fully automated expert system for the evaluation of IBZM SPECT studies.

PURPOSE: Visual reading of [(123)I]IBZM SPECT scans depends on the experience of the interpreter. Therefore, semi-quantification of striatal IBZM uptake is commonly considered mandatory. However, semi-quantification is time consuming and prone to error, particularly if the volumes of interest (VOIs) are positioned manually. Therefore, the present paper proposes a new software tool ("IBZM tool") for fully automated and standardised processing, evaluation and documentation of [(123)I]IBZM SPECT scans. METHODS: The IBZM tool is an easy-to-use SPM toolbox. It includes automated procedures for realignment and summation of multiple frames (motion correction), stereotactic normalisation, scaling, VOI analysis of striatum-to-reference ratio R, classification of R and standardised display. In order to evaluate the tool, which was developed at the University of Hamburg, the tool was transferred to the University of Hannover. There it was applied to 27 well-documented subjects: eight patients with multi-system atrophy (MSA), 12 patients with Parkinson's disease (PD) and seven controls. The IBZM tool was compared with manual VOI analysis. RESULTS: The sensitivity and specificity of the IBZM tool for the differentiation of the MSA subjects from the controls were 100% and 86%, respectively. The IBZM tool provided improved statistical power compared with manual VOI analysis. CONCLUSION: The IBZM tool is an expert system for the detection of reduced striatal D(2) availability on [(123)I]IBZM SPECT scans. The standardised documentation supports visual and semi-quantitative evaluation, and it is useful for presenting the findings to the referring physician. The IBZM tool has the potential for widespread use, since it appears to be fairly independent of the performance characteristics of the particular SPECT system used. The tool is available free of charge.

Adult↗
PubMedDate not supplied

A review of the literature on the etiology of capsular contracture and a pilot study to determine the outcome of capsular contracture interventions.

The etiology of capsular contracture is unclear and probably multifactorial. This review covers the literature on several proposed contracture factors, including filler material, implant placement, surface texture, and bacterial infection. The pilot study's goal was to test the feasibility of a data collection form, which could be used in a scaled-up study analyzing multiple surgeon's records. The goal of the expanded version of this study will be to determine the efficacy of available interventions for capsular contracture, including surveillance. The Breast Implant Public Health Project, LLC (BIPHP), piloted a retrospective review of outcomes in women who had interventions to relieve capsular contracture or had chosen a wait-and-watch approach. An evaluation of the efficacy of various treatments can help women decide if they want to pursue treatment at all and, if so, which treatment might offer them the best solution. BIPHP researchers (E.E.A., M.E.) developed a data collection form after reviewing records of three surgeons (B.C., W.P., V.L.Y.). During the data collection using the same records, we tested a randomization process to identify women with capsular contracture who underwent various interventions, including a wait-and-watch strategy, and those who had no mention of any intervention or waiting approach. Data were gathered on a total of 90 breasts with capsular contracture (scored Baker I-IV or qualitatively), of which 45 underwent a total of 102 interventions for capsular contracture. Interventions were classified as "closed capsulotomy," "surgical," or "watchful waiting." Closed capsulotomy was performed most often (47%), followed by surgery (29%) and watchful waiting (21%). Presurgical Baker scores averaged higher in breasts that underwent surgery (3.1) than for watchful waiting (2.5) or closed capsulotomy (2.3). Though closed capsulotomies had 100% of outcomes scoring "improved" or "same," 58% of the breasts underwent the procedure more than once, suggesting that the favorable outcome was short-lived. The wait-and-watch approach resulted in scores of either "same" or "worse"; surgery (open capsulotomy, repositioning, or capsulectomy) resulted in 79% improved, 16% same, and 5% worse outcomes in breasts with outcomes listed. In all intervention procedure categories, outcomes were frequently unavailable; they were noted only 60% of the time (52/87). The missing 40% may have resulted from the doctor's failure to note it in the chart, satisfied patients not returning for additional treatment, or dissatisfied patients seeking treatment elsewhere. Generally, the data collection forms and procedures were workable; however, we uncovered issues to address in the scale-up of this pilot study: (1) the outcome report rate was 60%; (2) though Baker scores are commonly used to evaluate the degree of capsular contracture, it seems that grade I may have different meanings for different surgeons, which would need to be clarified; (3) participating surgeons will need to divulge standard-of-care items that they may not have included in medical records, but routinely performed (e.g., patient massage, use of prophylactic antibiotics); and (4) records were initially separated by "implant," then researchers realized that a more useful collection would be by "breast." The latter approach captures the history of the breast in one record, which may be more important to contracture than the differences in implants. With the modifications discussed, the study can be scaled up to encompass as many records as necessary to achieve robust statistical power. These data will add to the existing literature regarding factors associated with capsular contracture and identify factors that affect the successful outcome of capsular contracture interventions.

Breast↗
PubMed2002

Single-dose metronidazole versus 5-day multi-drug antibiotic regimen in excision of pilonidal sinuses with primary closure: a prospective randomised controlled double-blinded study.

BACKGROUND AND AIMS: This pilot study examines whether single-dose intravenous metronidazole preoperatively is at least as effective as a broad-spectrum multi-drug regimen in preventing infection-related wound complications following excision of pilonidal sinuses with primary closure. PATIENTS AND METHODS: A double-blinded study with 50 patients randomised to receiving either a single drug (intravenous metronidazole 500 mg) prophylaxis preoperatively or multi-drug cover (intravenous cefuroxime 1.5 g and metronidazole 0.5 g preoperatively, and oral co-amoxiclav 375 mg 8-hourly postoperatively). They will be reviewed 1, 2 and 4 weeks postoperatively. The wound will be graded as: I, healthy; II, redness and swelling of edges; III, abscess related to a suture; IV, spreading wound infection; V, wound breakdown. Other factors considered are the distance from the lowest wound margin to the anal verge, and previous pilonidal sinus surgery. RESULTS: Results awaited. CONCLUSION: Single-dose metronidazole seems an appropriate and low-cost antibiotic to consider for prophylaxis in pilonidal sinus surgery. This study will form the base for a trial to be conducted in larger numbers as a randomised controlled trial in order to have statistical power.

Amoxicillin-Potassium Clavulanate Combination↗
PubMed2005

Single-dose metronidazole vs 5-day multi-drug antibiotic regimen in excision of pilonidal sinuses with primary closure: a prospective, randomized, double-blinded pilot study.

AIM: To compare infection-related wound complications following excision of pilonidal sinuses with primary closure using either single-dose intravenous (i.v.) administration of metronidazole preoperatively or a broad-spectrum multi-drug regimen. PATIENTS AND METHODS: This is a double-blinded study wherein 50 patients were randomized into receiving either single-drug (metronidazole 500 mg i.v.) prophylaxis preoperatively or multi-drug cover (cefuroxime 1.5 g i.v. and metronidazole 0.5 g i.v. preoperatively, and co-amoxiclav 375 mg orally 8-hourly postoperatively for 5 days). They were reviewed at 1, 2 and 4 weeks postoperatively. Wounds were graded as follows: I, healthy; II, redness and swelling of edges; III, abscess in relation to a suture; IV, spreading wound infection; and V, wound breakdown. Other factors considered were the distance from the lowest wound margin to the anal verge and previous local surgery. RESULTS: Fifty patients (38 men and 12 women, mean age 27 years) underwent pilonidal sinus surgery. At week 1, there was no difference in wound infection rates (p=0.9). However, there were significantly more wound infections in the single-drug group at week 2 (p<0.0001) and week 4 (p=0.03). Seventy-two per cent of all patients had complete wound healing at week 4. Distance from the anal verge and previous surgery did not affect wound infection rates (p> or =0.2). Treating such complications costs 73,219.20 dollars per 100 patients. CONCLUSION: A broad-spectrum 5-day regimen is superior to 'single-shot' antibiotic prophylaxis in preventing infection-related wound complications. However, this study needs to be conducted in a larger number of patients to have statistical power.

Adult↗
PubMed2005

Space radiation does not induce a significant increase of intrachromosomal exchanges in astronauts' lymphocytes.

Chromosome aberration analysis in astronauts has been used to provide direct, biologically motivated estimates of equivalent doses and risk associated to cosmic radiation exposure during space flight. However, the past studies concentrated on measurements of dicentrics and translocations, while chromosome intrachanges (inversions) have never been measured in astronauts' samples. Recent data reported in the literature suggest that densely ionizing radiation can induce a large fraction of intrachanges, thus leading to the suspicion that interchanges grossly underestimate the cosmic radiation-induced cytogenetic damage in astronauts. We have analyzed peripheral blood lymphocytes from 11 astronauts involved in short- or long-term space flights in low-Earth orbit using high-resolution multicolor banding to assess the frequency of intrachromosomal exchanges in both pre- and post-flight samples. We did not detect any inversions in chromosome 5 from a total of 2800 cells in astronauts' blood. In addition, no complex type exchanges were found in a total of 3590 astronauts' lymphocytes analyzed by multifluor fluorescence in situ hybridisation. We conclude that, within the statistical power of this study, the analysis of interchanges for biological dosimetry in astronauts does not significantly underestimate the space radiation-induced cytogenetic damage, and complex-type exchanges or intrachanges have limited practical use for biodosimetry at very low doses.

Astronauts↗
PubMed2006

Mortality from cardiovascular diseases in the German uranium miners cohort study, 1946-1998.

An increased risk of cardiovascular diseases after exposure to low doses of ionizing radiation has been suggested among the atomic bomb survivors. Few and inconclusive results on this issue are available from miner studies. A positive correlation between coronary heart disease mortality and radon exposure has been reported in the Newfoundland fluorspar miners study, yet low statistical power due to small sample size was of concern. To get further insight into this controversial issue, data from the German uranium miners cohort study were used, which is by far the largest miner study up to date. The cohort includes 59,001 male subjects who were employed for at least six months between 1946 and 1989 at the former Wismut uranium company in Eastern Germany. Exposure to radon, long-lived radionuclides and external gamma radiation was estimated by using a detailed job-exposure matrix. About 16,598 cohort members were deceased until 31 December 1998, including 5,417 deaths from cardiovascular diseases. Linear Poisson regression models were used to estimate the excess relative risk (ERR) per unit of cumulative radiation exposure after adjusting for attained age and calendar period. No trend in risk of circulatory diseases with increasing cumulative exposure to either radon [ERR per 100 working level month: 0.0006; 95% confidence limit (CI): -0.004 to 0.006], external gamma radiation (ERR per Sv: -0.26, 95% CI: -0.6 to 0.05) or long-lived radionuclides (ERR per 100 kBqh/m3: -0.2, 95% CI: -0.5 to 0.06), respectively, was observed. This was also true for the sub-group heart disease and stroke. Our findings do not support an association between cardiovascular disease mortality and exposure to radiation among miners, yet low doses and uncontrolled confounding hamper interpretation.

Adult↗
PubMed2002

Increased incidence of haematological cancer among physicians in a University Hospital.

OBJECTIVES: The oral report of eight cases of cancer over a period of 3 years among physicians working in a French University Hospital led us to conduct a retrospective cohort study to compare the incidence of cancer in these physicians with that of the general population living in the same area. METHOD: The cohort consisted of 940 physicians (72% male, 28% female) who had worked for at least 1 year in this hospital between 1945 and 1994 (a total of 10,693 person-years). The incidence of cancer among physicians was compared with that of the general population using a local cancer registry which has recorded all cancer cases occurring in the Department between 1979 and 1994. Standardised incidence ratio (SIR) was calculated for all causes of cancer and site by site. RESULTS: Although the global incidence of cancer did not differ from that of the general population (SIR=0.97; 95% confidence interval (CI) 0.59-1.5), a significantly increased incidence of haematological malignancy was found among physicians (SIR=5.45; 95% CI 2-11.9). CONCLUSIONS: These findings pointed out the risk of lymphatic and haematopoietic cancer among physicians who started working after 1945 when the first rules pertaining to protection from ionising radiation came into effect. However, limitations of this study such as limited statistical power and lack of individual exposure data should be considered in the interpretation of these findings. Possible aetiological factors responsible for these risks are discussed. Education about general safety protection programmes against carcinogenic risk factors including physical, biological and chemical agents still remains a priority among physicians.

Adult↗
PubMed2004

Effects of lumbar extensor fatigue and fatigue rate on postural sway.

Falls from heights resulting from a loss of balance are a major concern in the occupational setting. Previous studies have documented a deleterious effect of lower extremity fatigue on balance. The purpose of this study was to investigate the effect of lumbar extensor fatigue on balance during quiet standing. Additionally, the effects of fatigue rate on balance and balance recovery rate were assessed. Eight center-of-pressure-based measures of postural sway were collected from 13 participants, both before and after a protocol that fatigued the lumbar extensors to 60% of their unfatigued maximum voluntary exertion force. In addition, postural sway was measured for 30 min after the fatiguing protocol, at 5-min intervals, to quantify balance recovery rate during recovery from fatigue. Two different fatigue rates were achieved by fatiguing participants over either 10 min or 90 min. Results show an increase up to 58% in time-domain postural sway measures with lumbar extensor fatigue, but no change in frequency-domain measures. Fatigue rate did not affect the magnitude of these postural sway increases, nor did it affect the rate of balance recovery following fatigue. Statistical power for the latter result, however, was low. These results show that lumbar extensor fatigue increases postural sway and may contribute to fall-from-height accidents.

Adult↗
PubMed2006

Detection of length-dependent effects of tandem repeat alleles by 3-D geometric decomposition of craniofacial variation.

Topologically conservative morphological transformations typify the succession of species in the fossil record and also typify more subtle morphological variation within species. Isolation and quantification of morphological variation along its various intermingled modes becomes increasingly difficult as the structures under consideration increase in complexity. Here, we describe a comparative morphometric and genomic study in dogs in which complex three-dimensional craniofacial variation is mathematically distilled into simpler geometric components to test the hypothesis that incremental mutations at developmental loci result in simple geometric deformations of morphology. Combinations of candidate transforms are computationally evaluated for their ability to accurately transform a reference three-dimensional skull model into those of distinct breeds. A set of five simple basis functions are found to be sufficient to describe most craniofacial variation among dogs. Allele lengths of amino acid repeat length variants in developmental regulator genes, which frequently have quantitative effects on phenotype, were compared to geometric terms using Pearson correlation and regression. The coordinated quantitative representation of both phenotype and genotype improves the statistical power for the detection of causative genotype-phenotype relationships and enabled the characterization of the influence of Runx-2 coding repeat length on craniofacial variation among domestic dogs.

Animals↗
PubMed2002

Transmission disequilibrium test with discordant sib pairs when parents are available.

The transmission disequilibrium test (TDT) has been employed to map disease susceptibility loci (DSL), while being immune to the problem of population admixture. The customary TDT test (TDT(D)) was developed for affected child(ren) and their parents and was most often applied to case-parent trios. Recently, the TDT has been extended to the situations when (1) parents are not available but affected and nonaffected sibs from each family are available, (2) unrelated control-parent trios are available for combined analyses with case-parent trios (TDT(DC)), and (3) large pedigrees. For many diseases, affected children in the case-parent trios enlisted into the TDT(D) have unaffected sibs who can be recruited. We present an extension of the TDT by effectively incorporating one unaffected sib of each of the affected children in the case-parent trios into a single analysis (TDT(DS), where DS denotes discordant sib pairs). We have developed a general analytical method for computing the statistical power of the TDT(DS) under any genetic model, the accuracy of which is validated by computer simulations. We compare the power of the TDT(D), TDT(DC), and TDT(DS) under a range of parameter space and genetic models. We find that the TDT(DS) is generally more powerful than the TDT(DC) and TDT(D), particularly when the disease is prevalent (>30%) in the population. The relative power of the TDT(D) and the TDT(DS) largely depends upon the allele frequencies and genetic effects at the DSL, whereas the recombination rate, the degree of linkage disequilibrium, and the marker allele frequencies have little effect. Importantly, the TDT(DS) not only may be more powerful, it also has the advantage of being able to test for segregation distortion that may yield false linkage/association in the TDT(D).

Alleles↗
PubMed2006

Genome-wide linkage scan for prostate cancer susceptibility genes in men with aggressive disease: significant evidence for linkage at chromosome 15q12.

Epidemiological and twin studies have consistently demonstrated a strong genetic component to prostate cancer (PCa) susceptibility. To date, numerous linkage studies have been performed to identify chromosomal regions containing PCa susceptibility genes. Unfortunately, results from these studies have failed to form any obvious consensus regarding which regions are most likely to contain genes that may contribute to PCa predisposition. One plausible explanation for the difficulty in mapping susceptibility loci is the existence of considerable heterogeneity in the phenotype of PCa, with significant variation in clinical stage and grade of disease even among family members. To address this issue, we performed a genome-wide linkage scan on 71 informative families with two or more men with aggressive PCa. When only men with aggressive PCa were coded as affected, statistically significant evidence for linkage at chromosome 15q12 was detected (LOD=3.49; genome-wide p=0.005). Furthermore, the evidence for linkage increased when analyses were restricted to Caucasian-American pedigrees (n=65; LOD=4.05) and pedigrees with two confirmed aggressive cases (n=42, LOD=4.76). Interestingly, a 1-LOD support interval about our peak at 15q12 overlaps a region of suggestive linkage, 15q11, identified by a recent linkage study on 1,233 PCa families by the International Consortium for Prostate Cancer Genetics. Using a more rigid definition of PCa in linkage studies will result in a severe reduction in sample sizes available for study, but may ultimately prove to increase statistical power to detect susceptibility genes for this multigenic trait.

Alleles↗
PubMed2006

Meta-analysis shows association between the tryptophan hydroxylase (TPH) gene and schizophrenia.

A number of studies have suggested an association between schizophrenia and the tryptophan hydroxylase (TPH) and tyrosine hydroxylase (TH) genes. On the other hand, several studies attempting to replicate these findings have produced mixed results, possibly reflecting inadequate statistical power of the individual studies as well as the heterogeneity inherent in schizophrenia. In an attempt to clarify this inconsistency our meta-analysis has combined all the studies using multiple research methods published up to February 2006 to give a comprehensive picture of the role of three hydroxylase-related genes. The TPH A218C/A779C (OR = 1.18, 95% C.I. 1.06-1.33, P = 0.004) revealed a significant association with schizophrenia. However, the evidence for the TH and phenylalanine hydroxylase (PAH) genes was weak. No publication bias was detected in current studies. The findings, which may implicate the involvement of TPH in the pathogenesis of schizophrenia, have potentially important clinical, scientific and public health implications as well as providing a putative basis for the study of hydroxylase-related drugs. To our knowledge, this is the first meta-analysis of association between the three genes and schizophrenia.

Gene Frequency↗
PubMed2006

A classical likelihood based approach for admixture mapping using EM algorithm.

Several disease-mapping methods have been proposed recently, which use the information generated by recent admixture of populations from historically distinct geographic origins. These methods include both classic likelihood and Bayesian approaches. In this study we directly maximize the likelihood function from the hidden Markov Model for admixture mapping using the EM algorithm, allowing for uncertainty in model parameters, such as the allele frequencies in the parental populations. We determined the robustness of the proposed method by examining the ancestral allele frequency estimate and individual marker-location specific ancestry when the data were generated by different population admixture models and no learning sample was used. The proposed method outperforms a widely used Bayesian MCMC strategy for data generated from various population admixture models. The multipoint information content for ancestry was derived based on the map provided by Smith et al. (2004) and the associated statistical power was calculated. We examined the distribution of admixture LD across the genome for both real and simulated data and established a threshold for genome wide significance applicable to admixture mapping studies. The software ADMIXPROGRAM for performing admixture mapping is available from authors.

Algorithms↗