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PubMed2026

Agnostic polygenic prediction of weight loss after bariatric surgery.

A large interindividual variability in weight loss outcomes following bariatric surgery is reported. To ensure optimal management of patients, it is crucial to accurately identify candidates most likely to benefit the most from the intervention. Since genetic variants largely contribute to surgery response, polygenic scores (PGS) derived from genome-wide association studies (GWAS) could constitute valuable tools for clinical decision making. We developed and evaluated PGS to predict the weight loss response in 540 patients with a body mass index (BMI) of 35 kg/m2 or higher who underwent biliopancreatic diversion with duodenal switch. Summary statistics derived from BMI-derived GWAS, together with summary statistics from previously published GWAS of BMI and adiposity features, were used to construct, evaluate, and benchmark weight loss PGS. The full-adjusted BMI PGS model built in the entire cohort explained 39.6% of the mean-over-time excessive body weight loss (%EBWL), while the BMI-PGS built in the training dataset explained 38.9%. All benchmarked PGS based on BMI showed a significant relationship with mean-over-time %EBWL. These findings highlight the potential of BMI PGS in predicting weight loss after bariatric surgery and support their use as promising tools to improve the effectiveness of future antiobesity treatments.

Humans↗
PubMed2004

Effect of administering recombinant erythropoietin to women with postpartum anemia: a meta-analysis.

OBJECTIVES: Recombinant erythropoietin (rEpo) has been administered to women with postpartum anemia in an attempt to accelerate their increase in hemoglobin concentration and reduce postpartum transfusions. However, it is not clear whether such an approach can be supported by evidence and should be generally recommended. STUDY DESIGN AND METHODS: Medical and scientific literature from January 1990 to December 2002 was searched and studies that reported the administration of rEpo to women with postpartum anemia were evaluated. RESULTS: Eight evaluated studies reported an aggregate of 480 women; 300 rEpo recipients and 180 controls. Significant diversity in design was observed in rEpo dose, route of rEpo administration, iron supplementation, and baseline hemoglobin. No significant safety concerns were reported. In all five studies where it was reported, 4 to 7 days after beginning treatment, greater increases in hemoglobin concentration were observed among the rEpo recipients than among the controls. However, heterogeneity of results (Q-test statistic, p<0.01) indicated that it was not appropriate to apply summary statistics. The effect of rEpo on postpartum transfusion rate was not measurable by summary statistics because of the limited number of transfusions given (no transfusions among the 300 rEpo recipients vs two transfusions among the 180 controls). CONCLUSION: Administration of rEpo to women with postpartum anemia appears to be safe, and is associated with a trend toward a faster increase in hemoglobin concentration. However, its efficacy in terms of diminishing postpartum transfusions is unproven.

Adult↗
PubMed2003

Statistical methods for longitudinal research on bipolar disorders.

OBJECTIVES: Outcomes research in bipolar disorders, because of complex clinical variation over-time, offers demanding research design and statistical challenges. Longitudinal studies involving relatively large samples, with outcome measures obtained repeatedly over-time, are required. In this report, statistical methods appropriate for such research are reviewed. METHODS: Analytic methods appropriate for repeated measures data include: (i) endpoint analysis; (ii) endpoint analysis with last observation carried forward; (iii) summary statistic methods yielding one summary measure per subject; (iv) random effects and generalized estimating equation (GEE) regression modeling methods; and (v) time-to-event survival analyses. RESULTS: Use and limitations of these several methods are illustrated within a randomly selected (33%) subset of data obtained in two recently completed randomized, double blind studies on acute mania. Outcome measures obtained repeatedly over 3 or 4 weeks of blinded treatment in active drug and placebo sub-groups included change-from-baseline Young Mania Rating Scale (YMRS) scores (continuous measure) and achievement of a clinical response criterion (50% YMRS reduction). Four of the methods reviewed are especially suitable for use with these repeated measures data: (i) the summary statistic method; (ii) random/mixed effects modeling; (iii) GEE regression modeling; and (iv) survival analysis. CONCLUSIONS: Outcome studies in bipolar illness ideally should be longitudinal in orientation, obtain outcomes data frequently over extended times, and employ large study samples. Missing data problems can be expected, and data analytic methods must accommodate missingness.

Bipolar Disorder↗
PubMed2006

Modified Hudson-Kreitman-Aguade test and two-dimensional evaluation of neutrality tests.

There are a number of polymorphism-based statistical tests of neutrality, but most of them focus on either the amount or the pattern of polymorphism. In this article, a new test called the two-dimensional (2D) test is developed. This test evaluates a pair of summary statistics in a two-dimensional field. One statistic should summarize the pattern of polymorphism, while the other could be a measure of the level of polymorphism. For the latter summary statistic, the polymorphism-divergence ratio is used following the idea of the Hudson-Kreitman-Aguadé (HKA) test. To incorporate the HKA test in the 2D test, a summary statistic-based version of the HKA test is developed such that the polymorphism-divergence ratio at a particular region of interest is examined if it is consistent with the average of those in other independent regions.

Computer Simulation↗
PubMed2002

Interventions for increasing pedestrian and cyclist visibility for the prevention of death and injuries.

BACKGROUND: Pedestrians and cyclists account for nearly one in three of all road users killed and seriously injured in road traffic crashes. Late detection of other road users is one of the basic driver failures responsible for collisions. Aids to improve pedestrians and cyclist visibility have been used to avert potential collisions. However, the impact of these strategies on drivers' responses, and on pedestrian and cyclist safety is not known. OBJECTIVES: 1. To quantify the effect of visibility aids vs no visibility aids, and of different visibility aids on the occurrence of pedestrian and cyclist-motor vehicle collisions and injuries. 2. To quantify the effect of visibility aids vs no visibility aids, and of different visibility aids on drivers' detection and recognition responses. SEARCH STRATEGY: We searched the Cochrane Controlled Trials Register, the Injuries Group Specialised Register, MEDLINE, TRANSPORT, TRANSDOC from ECMT (European Conference of Ministers of Transport), IRRD (International Road Research Documentation), TRIS (Transportation Research Information Services), NRR (National Research Register), PsycInfo and PsycLit. SELECTION CRITERIA: 1. Randomised controlled trials and controlled before/after trials of the effect of visibility aids on the occurrence of pedestrian and cyclist-motor collisions and injuries. 2. Randomised controlled trials of the effect of visibility aids on drivers' detection and recognition responses. This included trials where the order of presentation of visibility aids was randomised or balanced using a Latin square design. DATA COLLECTION AND ANALYSIS: Two reviewers independently screened records, extracted data and assessed trial quality. MAIN RESULTS: We found no trials assessing the effect of visibility aids on the occurrence of pedestrian and cyclist-motor vehicle collisions and injuries. We identified 37 trials assessing the effect of visibility aids on drivers' responses. Fluorescent materials in yellow, red and orange colours improve detection and recognition in the daytime. For night-time visibility, lamps, flashing lights and retroreflective materials in red and yellow colours increase detection and recognition. Retroreflective materials arranged in a 'biomotion' configuration also enhance recognition. Substantial heterogeneity between and within the trials limited the possibility for meta-analysis. Summary statistics and descriptive summaries of the outcomes were presented for individual trials when appropriate. REVIEWER'S CONCLUSIONS: Visibility aids have the potential to increase visibility and enable drivers to detect pedestrians and cyclists earlier. Public acceptability of these strategies would merit further development. However, the effect of visibility aids on pedestrian and cyclist safety remains unknown. Studies which collect data on simple, meaningful outcomes are required.

Accidents, Traffic↗
PubMed2006

Interventions for increasing pedestrian and cyclist visibility for the prevention of death and injuries.

BACKGROUND: Pedestrians and cyclists account for nearly one in three of all road users killed and seriously injured in road traffic crashes. Late detection of other road users is one of the basic driver failures responsible for collisions. Aids to improve pedestrians and cyclist visibility have been used to avert potential collisions. However, the impact of these strategies on drivers' responses, and on pedestrian and cyclist safety is not known. OBJECTIVES: 1. To quantify the effect of visibility aids versus no visibility aids, and of different visibility aids on the occurrence of pedestrian and cyclist-motor vehicle collisions and injuries. 2. To quantify the effect of visibility aids versus no visibility aids, and of different visibility aids on drivers' detection and recognition responses. SEARCH STRATEGY: We searched the CENTRAL, the Cochrane Injuries Group specialised register, MEDLINE, TRANSPORT, National Research Register, PsycInfo and PsycLit. We searched the reference lists of included trials, contacted authors and searched the websites of relevant transport research organisations. The searches were last updated in April 2005. SELECTION CRITERIA: 1. Randomised controlled trials and controlled before-and-after studies of the effect of visibility aids on the occurrence of pedestrian and cyclist-motor collisions and injuries. 2. Randomised controlled trials of the effect of visibility aids on drivers' detection and recognition responses. This included trials where the order of presentation of visibility aids was randomised or balanced using a Latin square design. DATA COLLECTION AND ANALYSIS: Two authors independently screened records, extracted data and assessed trial quality. MAIN RESULTS: We found no trials assessing the effect of visibility aids on pedestrian and cyclist-motor vehicle collisions and injuries. We identified 39 trials assessing the effect of visibility aids on drivers' responses. Fluorescent materials in yellow, red and orange colours improve detection and recognition in the daytime. For night-time visibility, lamps, flashing lights and retroreflective materials in red and yellow colours increase detection and recognition. Retroreflective materials arranged in a 'biomotion' configuration also enhance recognition. Substantial heterogeneity between and within the trials limited the possibility for meta-analysis. Summary statistics and descriptive summaries of the outcomes were presented for individual trials when appropriate. AUTHORS' CONCLUSIONS: Visibility aids have the potential to increase visibility and enable drivers to detect pedestrians and cyclists earlier. Public acceptability of these strategies would merit further development. However, the effect of visibility aids on pedestrian and cyclist safety remains unknown. Studies which collect data on simple, meaningful outcomes are required.

Accidents, Traffic↗
PubMed2006

Analysis of repeated pregnancy outcomes.

Women tend to repeat reproductive outcomes, with past history of an adverse outcome being associated with an approximate two-fold increase in subsequent risk. These observations support the need for statistical designs and analyses that address this clustering. Failure to do so may mask effects, result in inaccurate variance estimators, produce biased or inefficient estimates of exposure effects. We review and evaluate basic analytic approaches for analysing reproductive outcomes, including ignoring reproductive history, treating it as a covariate or avoiding the clustering problem by analysing only one pregnancy per woman, and contrast these to more modern approaches such as generalized estimating equations with robust standard errors and mixed models with various correlation structures. We illustrate the issues by analysing a sample from the Collaborative Perinatal Project dataset, demonstrating how the statistical model impacts summary statistics and inferences when assessing etiologic determinants of birth weight.

Adolescent↗
PubMed1985

Neonatal data base and automated discharge summary using a personal computer and proprietary software.

A computerized neonatal data base and a program to develop automated neonatal discharge summaries were developed using a personal computer and proprietary software. The system has been relatively inexpensive, simple to operate, and easy to expand. The current program can produce a discharge summary in less than five minutes, as well as provide detailed summary statistics regarding patients admitted to the intensive care facility. The personal computer and proprietary software are a cost-effective mechanism of improving efficiency in obtaining neonatal statistics and discharge summaries.

Computers↗
PubMed2006

Four-fold table cell frequencies imputation in meta analysis.

Meta analysis is a collection of quantitative methods devoted to combine summary information from related but independent studies. Because research reports usually present only data reductions and summary statistics rather than detailed data, the reviewer must often resort to rather crude methods for constructing summary effect estimate suitable for meta analysis pooling methods. When the studies involve a binary variable, both number of events and sample sizes are required to compute pooled estimate and its confidence interval. Sometimes, only summary statistics and related confidence intervals are provided in the publication. Although it is possible to estimate the standard error of each study's effect measure using the confidence interval from each study, this lack of detailed data compels the reviewers to use the inverse variance method to perform meta analysis, or to exclude the works with incomplete data. This paper shows three methods to reconstruct four-fold tables when summary measures for binary data and related confidence intervals and sample sizes are provided. The methods are discussed through a wider application example to assess the reconstruction precision, and the impact of using reconstructed data on meta analysis results. These methods seem to yield a correct reconstruction if original measures are reported at least with two decimal places. Meta analysis results do not seem seriously affected by the use of reconstructed data. These methods allow the reviewer to use full meta analysis statistical tools, instead of the simple inverse variance method, and can greatly contribute to the completeness of systematic reviews.

Confidence Intervals↗
PubMed2006

The association between host susceptibility factors and uveal melanoma: a meta-analysis.

OBJECTIVE: To conduct a meta-analysis, using observational studies, to examine the association between host susceptibility factors and uveal melanoma. METHODS: A review of 132 published reports on risk factors for uveal melanoma revealed 10 case-control studies that provided enough information to calculate odds ratios (ORs) and standard errors for host susceptibility factors. Data from these studies were extracted and categorized. Summary statistics were calculated for all risk factors reported by at least 4 independent studies. RESULTS: Summary statistics using meta-analysis are presented as ORs and their 95% confidence intervals (CIs). Statistically significant risk factors include light eye color (OR, 1.75 [95% CI, 1.31-2.34]), using 10 studies (1732 cases); fair skin color (OR, 1.80 [95% CI, 1.31-2.47]), using 5 studies (586 cases); and ability to tan (OR, 1.64 [95% CI, 1.29-2.09]), using 6 studies (1021 cases). Blond or red hair color, using 7 studies (1012 cases), was not a statistically significant independent risk factor (OR, 1.02 [95% CI, 0.82-1.26]). CONCLUSION: This meta-analysis yielded strong evidence associating the host susceptibility factors of iris color, skin color, and ability to tan with uveal melanoma.

Case-Control Studies↗
PubMed2004

Effect of hepatitis C virus infection on the risk of non-Hodgkin's lymphoma: a meta-analysis of epidemiological studies.

Although a high prevalence of hepatitis C virus (HCV) infection among non-Hodgkin's lymphoma (NHL) patients had been reported, subsequent epidemiological studies conducted to examine a causal association between HCV and NHL have provided inconsistent results across studies. A strikingly positive association has been reported primarily from Italy and Japan, while no association was found in other regions of the world. To clarify the association between HCV and NHL, we conducted a systematic literature review. Eligible study designs were nested case-control studies, population-based case-control studies, and hospital-based case-control studies using non-cancer subjects as controls. The studies published through January 1991 to August 2003 were searched through Medline. Ultimately, 23 studies with 4049 NHL patients and 1,813,480 controls were identified. Summary statistics were crude odds ratios (ORs) comparing the anti-HCV seropositive and seronegative subjects. As we identified heterogeneity between studies, summary statistics were calculated based on a random-effect model. We did not find any evidence of publication bias. The major sources of variation were the use of blood donor controls and year of publication. The summary OR for NHL was 5.70 (95% confidence interval (CI), 4.09-7.96, P < 0.001). The subgroup analysis by phenotype showed a similar trend for B-cell (5.04, 95% CI: 3.59-7.06) and T-NHL (2.51, 95% CI: 1.39-4.56). In conclusion, we found a strongly positive association between anti-HCV seropositive test subjects and risk of NHL. Further biological studies examining this association are warranted.

Blood Donors↗
PubMed2005

Bridging the gap between statistical analysis and decision making in public health research.

Statisticians have eagerly taken on the role of presenting statistical summaries of quantitative data. In areas of health, this means providing point and interval estimates for quantities of interest such as diagnostic risks and treatment effects or providing curve estimates for quantities of interest such as survival probabilities across time. Methods for providing such summaries are highly formalized and constantly evolving. While decision making is the incentive for nearly all such efforts, the process that transforms statistical summaries into decisions usually remains informal and ad hoc. Statisticians have not eagerly accepted the role of promoting formalized decision-theoretic techniques. This paper will argue that the gap between statistical synthesis and decision making is an unnatural and undesirable one, because it undermines the impact of quantitative information. An argument for bridging the gap by expanding the role of statisticians will be presented.

Bayes Theorem↗
PubMed2003

Complications with using ratios for environmental data: comparing enantiomeric ratios (ERs) and enantiomer fractions (EFs).

Complications arise when ratios are used to present environmental data because ratios are an unbounded, multiplicative scale that can lead to asymmetrical (skewed) data distributions. Enantiomeric ratios (ERs), historically used in discussions of chiral signatures, often are published as mean ER+/-single-value standard deviation. Application of statistical summaries, such as the widely used sample mean and standard deviation, to skewed ratio data is misleading and often inappropriate. Comparison of statistically summarized ER and enantiomer fraction (EF) data (which are based on a bounded, additive scale) for a range of hypothetical values reveals substantial discrepancies when conversion between ER and EF formats is used. These discrepancies are largest when the ratio data are greater than one and have large variability, because the data are more skewed. In many cases, the use of fractions instead of ratios can help to minimize misrepresentation of environmental data, including chiral data. The use of nonparametric statistical summaries, e.g., median and percentiles, provides a more robust indicator of the typical value and spread for both ER and EF data.

Data Interpretation, Statistical↗
PubMed2000

Zygotic associations and multilocus statistics in a nonequilibrium diploid population.

The usual approach to characterizing and estimating multilocus associations in a diploid population assumes that the population is in Hardy-Weinberg equilibrium. The purpose of this study is to develop a set of summary statistics that can be used to characterize and estimate the multilocus associations in a nonequilibrium population. The concept of "zygotic associations" is first expanded to facilitate the development. The summary statistics are calculated using the distribution of a random variable, the number of heterozygous loci (K) found in diploid individuals in the population. In particular, the variance of K consists of single-locus and multilocus components with the latter being the sum of zygotic associations between pairs of loci. Simulation results show that the multilocus associations in the variance of K are detectable in a sample of moderate size (> or =30) when the sum of all pairwise zygotic associations is greater than zero and when gene frequency is intermediate. The method presented here is a generalization of the well-known development for the Hardy-Weinberg equilibrium population and thus may be of more general use in elucidating the multilocus organizations in nonequilibrium and equilibrium populations.

Analysis of Variance↗
PubMed1991

Risk for serious gastrointestinal complications related to use of nonsteroidal anti-inflammatory drugs. A meta-analysis.

OBJECTIVE: To describe the relative risk for serious gastrointestinal complications due to non-aspirin nonsteroidal anti-inflammatory drug (NSAID) exposure among NSAID users as well as in selected subgroups. DESIGN: Overview and meta-analysis. DATA IDENTIFICATION: A literature search of English-language studies examining the association between NSAIDs and adverse gastrointestinal events for the period 1975 to 1990 identified using MEDLINE and communicating with three internationally recognized experts. DATA ANALYSIS: A qualitative summary of study characteristics and a critical appraisal of study quality were done. The results of 16 primary studies were selected and combined statistically. Summary estimates were weighted by sample size and quality score. MAIN RESULTS: The overall odds ratio of the risk for adverse gastrointestinal events related to NSAID use, summarized from 16 studies (9 case-control and 7 cohort) was 2.74 (95% Cl, 2.54 to 2.97). The summary odds ratios were as follows: elderly patients, (aged greater than or equal to 60 years), 5.52 (Cl, 4.63 to 6.60); patients under 65 years of age, 1.65 (Cl, 1.08 to 2.53); women, 2.32 (Cl, 1.91 to 2.82); and men, 2.40 (Cl, 1.85 to 3.11). The summary odds ratio for NSAID users receiving concomitant corticosteroids compared with NSAID users not receiving corticosteroids was 1.83 (Cl, 1.20 to 2.78). The summary odds ratio for the first gastrointestinal event was 2.39 (Cl, 2.16 to 2.65). The relative risk for a subsequent or unspecified gastrointestinal event was 4.76 (Cl, 4.05 to 5.59). The summary odds ratio for less than 1 month of NSAID exposure was 8.00 (Cl, 6.37 to 10.06); for more than 1 month but less than 3 months of exposure, the summary odds ratio was 3.31 (Cl, 2.27 to 4.82); and for more than 3 months of exposure, the summary odds ratio was 1.92 (Cl, 1.19 to 3.13). CONCLUSIONS: Users of NSAIDs are at approximately three times greater relative risk for developing serious adverse gastrointestinal events than are nonusers. Additional risk factors include age greater than 60 years, previous history of gastrointestinal events, and concomitant corticosteroid use. Another possible risk factor is the first 3 months of NSAID therapy. The risk for serious gastrointestinal events appears to be equal among men and women. These data represent summary statistics from 16 studies and cannot be considered generalizable to all NSAID users.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1993

A technique for summarizing longitudinal data.

Many studies collect longitudinal data but do not use them efficiently. We propose a technique for reducing a set of longitudinal data into four common summary statistics together with time. These statistics can be used in place of the raw data in further analyses, for example in a regression analysis. Instead of arbitrarily choosing the summary statistics, we derive them mathematically, thus justifying their use. This simplifies the subsequent analyses, and also improves the interpretation of the results. An example from the Framingham Heart Study illustrates the procedure.

Bias↗
PubMed1999

Adjusting estimates of alveolar bone loss for missing observations: developing and testing a general model.

The occurrence of missing teeth is a vexing and growing problem in epidemiological studies of dental disease. The number of units of measurement (i.e., teeth/tooth sites) varies between persons and may affect summary statistics in descriptive studies as well as in analytical studies. The purpose of the present study was to develop a general model to adjust summary statistics for missing teeth. The proposed method was applied to alveolar bone loss in current smokers, former smokers, and non-smokers, from 45 to 64 years of age (n = 812). Alveolar bone loss was measured on bitewing radiographs. The adjustment method was based on the assumption that the probability of losing a tooth was an increasing function of alveolar bone loss. The main finding of the present study was that mean alveolar bone loss increased after adjustment for the number of missing teeth. This increase was larger for current smokers than for non-smokers, indicating that the effects of smoking were slightly underestimated when missing sites were ignored. Further research is required for the model to be applied to other data, estimating different types of dental disease with various degrees of disease prevalence and various numbers of missing teeth, and for validating the adjustment method by means of longitudinal data.

Age Factors↗