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PubMed2006

Field evaluation of the Welch Allyn SureSight vision screener: incorporating the vision in preschoolers study recommendations.

INTRODUCTION: The prospective Vision in Preschoolers (VIP) study evaluated 11 methods of screening and proposed referral criteria for the Welch Allyn SureSight(trade mark) Vision Screener with 90% and 94% specificity. The SureSight had a higher sensitivity than most other screening techniques when these criteria were applied. We evaluated the usefulness of these criteria in a field study of healthy preschool children. METHODS: The SureSight software was altered to recommend referral using the VIP referral criteria with 90% specificity. Lions Club volunteers screened preschool children throughout Tennessee. Referred children underwent comprehensive eye examinations with cycloplegic refraction. Examination failure criteria were based upon published standards. Reanalysis using the 94% specificity criteria was then performed. Outcomes included referral rate and positive predictive value. RESULTS: The SureSight was used to screen 4,733 children, and screening was successful in 99.7% of children. The referral rate using the 90% specificity criteria was 12.2%. Most children (73%) were referred for suspected astigmatism. The positive predictive value was 30%. Using the 94% specificity criteria from the VIP study decreased the referral rate to 7.9% and substantially decreased over referral for suspected astigmatism; however, several anisometropes went undetected. Higher specificity was achieved by raising astigmatism referral criteria to 2.2 diopters while leaving the anisometropia criteria unchanged. CONCLUSIONS: The SureSight can be used successfully for preschool screening in the field provided that criteria with high specificity are incorporated into the instrument's software program. Higher rates of positive predictive value can be achieved without jeopardizing sensitivity by raising astigmatism referral criteria to 2.2 diopters.

Amblyopia↗

PubMed2005

Trials and tribulations of non-inferiority: the ximelagatran experience.

Ximelagatran is a novel oral direct thrombin inhibitor that offers a number of advantages over the standard treatment, warfarin, in patients with atrial fibrillation. Two large clinical trials, one open-label (Stroke Prevention Using Oral Thrombin Inhibitor in Atrial Fibrillation [SPORTIF] III), one double-blind (SPORTIF V), have compared the efficacy and safety of fixed-dose ximelagatran without anticoagulation monitoring with dose-adjusted warfarin using a non-inferiority design. On the basis of the results, the investigators concluded that ximelagatran was just as effective as warfarin in preventing stroke or systemic embolism (the primary end point), because the pre-specified non-inferiority criterion was met. Reanalysis of the data with rather conservative interpretive criteria, however, revealed a number of deficiencies: 1) an unreasonably generous margin that was potentially biased toward non-inferiority, given the low baseline event rate of warfarin; 2) the inappropriateness of the analytical method used to estimate the non-inferiority margin; 3) a lack of confidence that ximelagatran retains at least 50% of warfarin's effect (a prerequisite to the establishment of non-inferiority); 4) significant heterogeneity in the magnitude of efficacy observed in the two trials; and 5) safety concerns regarding increased liver toxicity with ximelagatran without a significant offsetting advantage in major bleeding. This imbalance in the benefit-risk profile materially undermines the investigators' claim of non-inferiority of ximelagatran and led the Food and Drug Administration to reject the sponsor's application for ximelagatran. Despite published conclusions to the contrary, we conclude that ximelagatran has not been shown to be non-inferior to warfarin. Such determinations of non-inferiority are highly dependent on the underlying assumptions, and graphical sensitivity analyses make this dependence explicit.

Anticoagulants↗

PubMed2006

Clinical characteristics predict benefits from eptifibatide therapy during coronary stenting: insights from the Enhanced Suppression of the Platelet IIb/IIIa Receptor With Integrilin Therapy (ESPRIT) trial.

OBJECTIVES: In order to determine a differential benefit from treatment, we compared the long-term outcome of high-risk versus low-risk patients and evaluated survival free from death or myocardial infarction at one year. BACKGROUND: Newer anticoagulant strategies during percutaneous coronary intervention have necessitated a reanalysis of the role of intravenous GP IIb/IIIa inhibitors. The Enhanced Suppression of the Platelet IIb/IIIa Receptor with Integrilin Therapy trial randomized 2,064 patients undergoing nonurgent coronary stent implantation to eptifibatide or placebo. METHODS: High-risk characteristics were defined as age >75 years, diabetes, elevated cardiac markers, ST-segment elevation myocardial infarction within 7 days, or unstable angina within 48 h of randomization. Age <5 years, absence of diabetes, and any other reason for admission were considered low risk characterstics. RESULTS: There were 1,018 patients in the high-risk group (50.8% eptifibatide, 49.2% placebo) and 1,045 patients in the low-risk group (50.0% eptifibatide, 50.0% placebo). Baseline demographics were similar in both groups except for more hypertension (63% vs. 55%, respectively), peripheral vascular disease (8.2% vs. 5.2%, respectively), prior stroke (5.5% vs. 3.2%, respectively), and female gender (33% vs. 22%, respectively) in the high-risk than the low-risk group. At one year, the composite end point of death or myocardial infarction occurred in 15.89% of placebo patients and 7.99% of eptifibatide patients in the high-risk group and 9.02% of the placebo and 8.11% of eptifibatide patients in the low-risk group. CONCLUSIONS: Although eptifibatide treatment improved outcomes for all patients, preprocedural clinical characteristics can define a subgroup of patients who may derive greatest benefit from its use during coronary stent placement.

Aged↗

PubMed2004

Patterns of intra-cluster correlation from primary care research to inform study design and analysis.

OBJECTIVE: To provide information concerning the magnitude of the intraclass correlation coefficient (ICC) for cluster-based studies set in primary care. STUDY DESIGN AND SETTING: Reanalysis of data from 31 cluster-based studies in primary care to estimate intraclass correlation coefficients from random effects models using maximum likelihood estimation. RESULTS: ICCs were estimated for 1,039 variables. The median ICC was 0.010 (interquartile range [IQR] 0 to 0.032, range 0 to 0.840). After adjusting for individual- and cluster-level characteristics, the median ICC was 0.005 (IQR 0 to 0.021). A given measure showed widely varying ICC estimates in different datasets. In six datasets, the ICCs for SF-36 physical functioning scale ranged from 0.001 to 0.055 and for SF-36 general health from 0 to 0.072. In four datasets, the ICC for systolic blood pressure ranged from 0 to 0.052 and for diastolic blood pressure from 0 to 0.108. CONCLUSION: The precise magnitude of between-cluster variation for a given measure can rarely be estimated in advance. Studies should be designed with reference to the overall distribution of ICCs and with attention to features that increase efficiency.

Cluster Analysis↗

PubMed2005

A Bayesian approach to evaluating net clinical benefit allowed for parameter uncertainty.

BACKGROUND AND OBJECTIVE: Although randomized controlled trials (RCTs) are conducted to establish whether novel interventions work on average in the patient population, there is a growing desire to move to a more individualized approach to evaluation. The potential benefits and harms of a treatment policy may differ between individuals. If these benefits and harms are not evaluated distinctly, and in a quantitative framework, transparency can be lost in the decision-making process. METHODS: Glasziou and Irwig have outlined the concept of net clinical treatment benefit for identifying the patients for whom the potential benefits of treatment outweigh the possible side effects. This study revisits the decision whether to use warfarin to treat atrial fibrillation. In this analysis, RCT and various sorts of observational data are synthesized. RESULTS: This reanalysis brings into question the conclusions of the original analysis on who would benefit from warfarin; however, caution is advised, due to limitations in the quality of life data available. CONCLUSION: A fully realized Bayesian implementation of the model is presented. This provides a framework for including uncertainty related to the estimation of all model parameters, and permits both direct probability statements and credible intervals for specific patient groups to be expressed.

Anticoagulants↗

PubMed2006

Publication bias affected the estimate of postoperative nausea in an acupoint stimulation systematic review.

BACKGROUND AND OBJECTIVE: To assess the effect of publication bias and country effect on the results and conclusion of a systematic review of wrist P6 acupoint stimulation for the prevention of postoperative nausea and vomiting. METHODS: Reanalysis of a systematic review of 26 randomized trials comparing P6 acupoint stimulation with sham published in the Cochrane Database of Systematic Reviews using the Copas' sensitivity approach. RESULTS: If it is assumed that all studies that have ever been carried out are included, or that those selected for review are truly representative of all such studies, then the estimated relative risk (RR) for nausea was 0.71 (95% CI: 0.58 to 0.88, P<.01) and for vomiting was 0.70 (95% CI: 0.56 to 0.88, P<.01) after adjusting for country effect. For nausea, adjustment for publication bias suggests that the risk has been overestimated. If around 33% of studies have been unpublished, the RR of nausea (0.92, 95% CI: 0.80 to 1.06, P=.25) is no longer significant. For vomiting, however, there is no strong evidence of publication bias. The number of unpublished studies required to substantially overturn the above significant result is implausibly large. CONCLUSION: Publication bias affects the published estimate of postoperative nausea, not vomiting.

Humans↗

PubMed2005

Numerical simulations of radon as an in situ partitioning tracer for quantifying NAPL contamination using push-pull tests.

Presented here is a reanalysis of results previously presented by [Davis, B.M., Istok, J.D., Semprini, L., 2002. Push-pull partitioning tracer tests using radon-222 to quantify non-aqueous phase liquid contamination. J. Contam. Hydrol. 58, 129-146] of push-pull tests using radon as a naturally occurring partitioning tracer for evaluating NAPL contamination. In a push-pull test where radon-free water and bromide are injected, the presence of NAPL is manifested in greater dispersion of the radon breakthrough curve (BTC) relative to the bromide BTC during the extraction phase as a result of radon partitioning into the NAPL. Laboratory push-pull tests in a dense or DNAPL-contaminated physical aquifer model (PAM) indicated that the previously used modeling approach resulted in an overestimation of the DNAPL (trichloroethene) saturation (S(n)). The numerical simulations presented here investigated the influence of (1) initial radon concentrations, which vary as a function of S(n), and (2) heterogeneity in S(n) distribution within the radius of influence of the push-pull test. The simulations showed that these factors influence radon BTCs and resulting estimates of S(n). A revised method of interpreting radon BTCs is presented here, which takes into account initial radon concentrations and uses non-normalized radon BTCs. This revised method produces greater radon BTC sensitivity at small values of S(n) and was used to re-analyze the results from the PAM push-pull tests reported by Davis et al. The re-analysis resulted in a more accurate estimate of S(n) (1.8%) compared with the previously estimated value (7.4%). The revised method was then applied to results from a push-pull test conducted in a light or LNAPL-contaminated aquifer at a field site, resulting in a more accurate estimate of S(n) (4.1%) compared with a previously estimated value (13.6%). The revised method improves upon the efficacy of the radon push-pull test to estimate NAPL saturations. A limitation of the revised method is that 'background' radon concentrations from a non-contaminated well in the NAPL-contaminated aquifer are needed to accurately estimate NAPL saturation. The method has potential as a means of monitoring the progress of NAPL remediation.

Computer Simulation↗

PubMed2004

Ratio variables in regression analysis can give rise to spurious results: illustration from two studies in periodontology.

OBJECTIVES: For over a century, statisticians have highlighted concerns about the inappropriate use of ratio variables in correlation and regression analysis. However, little attention has been paid to these concerns in medical and dental research. The use of ratio variables in correlation and regression analysis can give rise to spurious results due to inappropriate model specification and mathematical coupling, leading to serious misinterpretation of data and consequently to incorrect study conclusions. METHODS: Data were reanalysed from two recently published articles: one on the efficacy of guided tissue regeneration on root coverage; the other a randomised controlled trial comparing three surgical approaches in the treatment of periodontal infrabony defects. The reanalysis was performed to examine whether the assumptions behind the correlation/regression analyses have been seriously violated in these two studies, and to see if the interpretation of results is tenable. RESULTS: Use of ratio variables seriously violated the assumptions underpinning the statistical methods utilised in these two studies, and consequently the conclusions were substantially misleading. Recommendations made in these studies were not tenable. CONCLUSIONS: The reanalyses illustrate how the inappropriate use of ratio variables remains prevalent in dental research, leading to incorrect interpretation of the evidence. This emphasises the need for collaboration between clinicians and statisticians to avoid the risk of yielding erroneous conclusions from flawed statistical analyses.

Alveolar Bone Loss↗

PubMed2003

Overview of the ISCE ECG "genome project".

The International Society for Computerized Electrocardiography (ISCE) "genome" project was begun at the end of 2000 to explore mechanisms for development of a cross-platform electrocardiogram (ECG) database. Ultimate feasibility of this project is based on established interactive cooperation of clinical investigators, engineers, and industry within the ISCE framework. The US Food and Drug Administration (FDA) mandate for centralized access to digitized ECG waveforms used in clinical trials provides a complementary stimulus to technologies that facilitate ECG database development. The constituency of ISCE is interested in acquisition and analysis of data from both standard 12-lead (resting) ECG and ambulatory (monitoring) ECG. Support for project goals from industry, at the Trustee as well as at the engineering level, has led to initial focus on the resting ECG. A one-year pilot project has been proposed to establish and implement software methodology for transmission, storage, and integrated reanalysis of digitized ECG waveforms provided by several major manufacturers. Beyond data acquisition, storage, and analysis, a number of critical issues are associated with database development. These include definition of clinically relevant "gold" standards, acquisition and validation of non-ECG data, protection of patient privacy, control and ownership of data, and accessibility and use of the database. However, implementation of the pilot project is a necessary first step, since all issues become moot without technical cooperation for shared formatting and analysis.

Databases as Topic↗

PubMed2006

Data-driven quality improvement in the Emergency Department at a level one trauma and tertiary care hospital.

To demonstrate how a comprehensive and internally driven Continuous Quality Improvement (CQI) program was designed and implemented in our Emergency Department (ED) in 1999. This program involved monthly data collection and analysis, data-driven process change, staff education in the core concepts of quality, and data reanalysis. Data components collected during the program included census data, physician profiling, and focused clinical audits. CQI measures collected at the beginning of the program and quarterly included: (1) CQI metric data (turnaround times [TAT] and rates of left against medical advice [AMA] or left without being seen [LWOBS]), (2) rates and nature of patient complaints, and (3) results of patient satisfaction surveys performed by an outside consulting firm contracted by hospital administration. During the 4 years since its implementation the program demonstrated improvement in all measured areas. Despite an increase in patient volume of 32% to nearly 37,000 visits/year, and only minimal staffing adjustments, the mean quarterly TAT decreased from 183 min to 165 min (9.8% decrease), the rate of complaints dropped by 56.1% (2.1 per 1000 patients to 0.92), and patients leaving AMA or LWOBS decreased 66.7% from 2.7% to 0.9%. Overall, 44.8% of ED patients rated their care as "excellent." In summary, we demonstrate how a comprehensive quality improvement program was structured and implemented at a tertiary care center and how such a program demonstrated improvement in specific CQI parameters.

Academic Medical Centers↗

PubMed2006

Middle Pleistocene handaxes from the Korean Peninsula.

We present four biface assemblages from an archaeologically poorly known region of the Old World: Middle Pleistocene Korea. The handaxes are derived from a series of Middle Pleistocene localities in the Imjin/Hantan River Basins (IHRB) in Korea. The best known of these localities is Chongokni, although a number of equally important sites in the IHRB have been discovered and excavated over the course of the past two decades (e.g., Kumpari, Chuwoli, and Kawoli). Reanalysis of the age of the Chongokni deposits suggests a hominin occupation between 350-300 ka. Comparative study of the IHRB handaxes with the well-known bifacial implements from Olorgesailie (Kenya) and Hunsgi-Baichbal (India) indicates that the often-noted "thick" trait of the East Asian handaxes differs at a statistical level across the various regions of the Old World. The finds from the IHRB sites, and the Chinese sites of Bose and Dingcun that contain handaxes-like implement, question the validity of the Movius Line sensu stricto. However, why East Asian Middle Pleistocene hominins did not consistently produce more refined bifaces across broader regional and/or temporal facies, remains open to question. Thus, the absence of similar sites in wider areas of Early and Middle Pleistocene East Asia suggests that the Movius Line sensu lato is still supportable and warrants additional detailed cross comparative studies of the stone toolkits east and west of the line.

Animals↗

PubMed2004

Pitfalls in IMRT treatment planning with the CadPlan-Helios system.

The CadPlan-Helios treatment planning system for intensity-modulated radiation therapy (IMRT) includes some physical parameters that are specified by the planner, and thus can be subjectively interpreted. The choice of the value of these parameters strongly depends on the practical experience of the planner. This paper presents some extremes of the optimization constraints, to illustrate some traps of IMRT planning. The examples used in this paper are not directly related to clinical situations and some problems were deliberately exaggerated. Treatment fields were defined as recommended by Memorial Sloan-Kettering Cancer Center procedures for prostate IMRT. Prostate plans were arranged using a 5-field technique and 20-MV photon beam. The target and critical structures were defined and contoured for CadPlan-Helios. All computer calculations were performed for the same field arrangement. The following optimization parameters and factors are presented and analyzed in examples to visualize the importance of each parameter: dose-volume constraints and priority factors, scatter distance, maximum number of iterations and termination tolerance. The presented analysis strongly suggests that all constraints and parameters should be recorded in individual planning charts because without their nominal values, any reanalysis or dose recalculation may be difficult.

Clinical Competence↗

PubMed2006

Within-host dynamics of antigenic variation.

Genomes of some parasites contain dozens of alternative and highly diverged surface antigens, of which only a single one is expressed in any cell. Individual cells occasionally change expression of their surface antigen, allowing them to escape immune surveillance. These switches appear to occur in a partly random way, creating a diverse set of antigenic variants. In spite of this diversity, the parasitemia develops as a series of outbreaks, in which each outbreak is dominated by relatively few antigenic types. Host-specific immunity eventually clears the dominant antigenic types, and a new outbreak follows from antigenic types that have apparently been present all along at low frequency. This pattern of sequential dominance by different antigenic types remains unexplained. We review the five most prominent theories, which have developed mainly from studies of the protozoans Trypanosoma and Plasmodium, and the bacterial spirochete Borrelia. The most promising theories depend on some combination of mechanisms to create favored connectivity pathways through the matrix of transitions between variants. Favored pathways may arise from biased switches at the molecular level of gene expression or from biases imposed by immune selection. We illustrate the concept of connectivity pathways by reanalysis of data on transitions between variants from Borrelia hermsii.

Animals↗

PubMed2006

Comparison of chaetognath mitochondrial genomes and phylogenetical implications.

Two complete mitochondrial genomes (mtDNAs) of chaetognaths, Spadella cephaloptera and Paraspadella gotoi, have been recently published. These genomes are highly unusual. They are the smallest metazoan mtDNAs so far known; atp6 and atp8 genes are missing; lastly, our reanalysis has evidenced that, contrarily to what has been previously published for one sequence, both contain a unique transfer RNA (tRNA(Met)) evidencing that both have the same gene content. Indeed, even if the gene order seems very different, two gene blocks are conserved. In addition, comparison of gene arrangement suggests phylogenetical relationships between chaetognaths and some lophotrochozoa like annelids and molluscs.

Animals↗

PubMed2006

Temporal neural networks for downscaling climate variability and extremes.

This paper presents an application of temporal neural networks for downscaling global climate models (GCMs) output. Because of computational constraints, GCMs are usually run at coarse grid resolution (in the order of 100s of kilometres) and as a result they are inherently unable to present local sub-grid scale features and dynamics. Consequently, outputs from these models cannot be used directly in many climate change impact studies. This research explored the issues of 'downscaling' the outputs of GCMs using a temporal neural network (TNN) approach. The method is proposed for downscaling daily precipitation and temperature series for a region in northern Quebec, Canada. The downscaling models are developed and validated using large-scale predictor variables derived from the National Center for Environmental Prediction (NCEP) reanalysis data set. The performance of the temporal neural network downscaling model is also compared to a regression-based statistical downscaling model with emphasis on their ability in reproducing the observed climate variability and extremes. The downscaling results for the base period (1961-2000) suggest that the TNN is an efficient method for downscaling both daily precipitation as well as daily maximum and minimum temperature series. Furthermore, the different model test results indicate that the TNN model mostly outperforms the statistical models for the downscaling of daily precipitation extremes and variability.

Climate↗

PubMed2004

Betel quid without tobacco as a risk factor for oral precancers.

The IARC monographs recently classified chewing betel quid without tobacco as a human carcinogen. Several studies in Taiwan have reported that betel quid without tobacco may increase the risk of oral precancers such as oral leukoplakia and oral submucous fibrosis. However in India, since most betel quid chewers prefer to add tobacco to the quid, the independent effect of betel quid on the risk of oral precancers is difficult to assess and has not yet been fully explored. We conducted a large case-control study in Kerala, India, including 927 oral leukoplakia cases, 170 oral submucous fibrosis cases, 100 erythroplakia cases, 115 multiple oral precancer cases and 47,773 controls. The focus of this reanalysis is on the minority of individuals who chewed betel quid without tobacco. Among nonsmokers and nondrinkers, chewing betel quid without tobacco conferred ORs of 22.2 (95%CI = 11.3, 43.7) for oral leukoplakia, 56.2 (95%CI = 21.8, 144.8) for oral submucous fibrosis, 29.0 (95%CI = 5.63, 149.5) for erythroplakia and 28.3 (95%CI = 6.88, 116.7) for multiple oral precancers, after adjustment for age, sex, education and BMI. Dose-response relationships were observed for both the frequency and duration of betel quid chewing without tobacco on the risk of oral precancers. In conclusion, our study supports the hypothesis that chewing betel quid without tobacco elevates the risks of various oral precancers.

Adult↗

PubMed2004

Lessons learned from a multiple-dose post-operative analgesic trial.

Patients undergoing major surgery often require several days of post-operative analgesic management. However, little data are available on the course of post-operative pain during this period. Such data would be extremely helpful in planning treatment, formulating pain management guidelines, and determining how to construct multiple-dose post-operative analgesic clinical trials. The objectives of this study were to determine (1) if post-operative pain severity, as measured by a modified version of the Brief Pain Inventory (BPI), can be categorized as mild, moderate, or severe in terms of modified BPI pain interference scores, (2) the relationship between modified BPI pain ratings and responses to a categorical item that specifically measures post-sternotomy pain, and (3) the relationship between global ratings of study medication effectiveness and other pain measures. This study is a reanalysis of data from patients who underwent coronary artery bypass graft procedures. We found that the pain severity level cut points developed for chronic pain apply equally well to post-operative pain. Based on this classification scheme, 18% of patients reported moderate pain after day 3, while 14% reported severe pain. Only 9% of patients reported experiencing moderate-to-severe pain approximately 2 weeks later, at the end of the study. Describing pain as mild, moderate, or severe could be a simple, meaningful clinical trial outcome measure. Because most patients experience only mild pain 6 days after surgery, long-term clinical trials of post-operative pain control may be more efficient and cost-effective if they focus on the subset of patients with persistent moderate or severe pain.

Aged↗

PubMed2005

Electroencephalography in neonatal seizures: comparison of a reduced and a full 10/20 montage.

This study compares a reduced electrode montage (9 electrodes) with the full 10/20 electrode montage for the ability to detect and characterize neonatal seizures and background electroencephalographic (EEG) characteristics, utilizing new digital technology allowing "remontage" of previously acquired records. A total of 151 neonatal EEG records were retrospectively and blindly analyzed by two readers. Records were first analyzed for seizure number, topography, duration, and characteristics of EEG background using the reduced montage, before reanalysis with the full montage. One hundred eighty-seven seizures were identified in 31 ictal recordings using the full montage. Using the reduced montage, 166 seizures were identified in 30 records. The sensitivity and specificity of the reduced montage for detecting electrographic seizures was 96.8% and 100% respectively. In only one patient's record, the single seizure was missed altogether. For grading background abnormalities, the sensitivity and specificity of reduced montage was 87% and 80%. Although there are inherent weaknesses in reduced montages with respect to both underestimation and overestimation of seizure number, a nine-electrode reduced montage can be a sensitive tool for identification of neonatal seizures and assessment of background characteristics of neonatal electroencephalography.

Brain Mapping↗