bluuebunny/crossref_metadata_2025_split huggingface dataset:
Likelihood‐based confidence intervals for a log‐normal mean
Authors: Wu Jianrong , Wong A. C. M. , Jiang Guoyong 
Published: May 2003

AbstractTo construct a confidence interval for the mean of a log‐normal distribution in small samples, we propose likelihood‐based approaches – the signed log‐likelihood ratio and modified signed log‐likelihood ratio methods. Extensive Monte Carlo simulation results show the advantages of the modified signed log‐likelihood ratio method over the signed log‐likelihood ratio method and other methods. In particular, the modified signed log‐likelihood ratio method produces a confidence interval with a nearly exact coverage probability and highly accurate and symmetric error probabilities even for extremely small sample sizes. We then apply the methods to two sets of real‐life data. Copyright © 2003 John Wiley & Sons, Ltd.
Estimates, power and sample size calculations for two‐sample ordinal outcomes under before–after study designs
Authors: Strickland Pamela A. Ohman , Lu Shou‐En 
Published: May 2003

AbstractSample size calculations are given for comparing two groups of subjects, typically referring to active and non‐active intervention groups, on an ordinal outcome in experiments where the subjects are measured before and after intervention. These calculations apply to log‐odds models with random intercepts, treatment, time and treatment‐by‐time interaction terms, the latter being the term of interest. The assumed forms of the odds ratios are flexible, allowing for proportional odds, adjacent categories, or other conditional models for ordinal responses. Simulations studies show that, for given sample sizes, the nominal and actual powers of the proposed test are similar. Copyright © 2003 John Wiley & Sons, Ltd.
A modified large‐sample approach to approximate interval estimation for a particular intraclass correlation coefficient
Authors: Cappelleri Joseph C. , Ting Naitee 
Published: May 2003

AbstractWe consider the problem of constructing a confidence interval for the intraclass correlation coefficient in an interrater reliability study when both raters and subjects are random effects in a two‐way random effects model. A simulation study is conducted to investigate and compare the interval coverage per cents of three methods of approximation: (i) Satterthwaite's two moments, the standard approach; (ii) modified three moments, a newer approach; and (iii) modified large sample, the newest approach for this particular problem. One‐sided lower and two‐sided bounds are examined. For the two‐moment approach, coverage of confidence intervals can be understated for not only one‐sided bounds but also two‐sided bounds. Coverage of confidence intervals for the modified large‐sample approach is either correct or conservative and provides narrower two‐sided widths than the modified three‐moment approach, which can understate coverage on one‐sided and two‐sided bounds for two or three raters. The competing methods are illustrated with data from a reliability study of four raters evaluating the number of decayed, missing, and filled surfaces in the permanent teeth of ten subjects. Overall, the modified large‐sample approach provides the most satisfactory performance of the three methods. Copyright © 2003 John Wiley & Sons, Ltd.
Age‐conditional probabilities of developing cancer
Authors: Fay Michael P. , Pfeiffer Ruth , Cronin Kathleen A. , Le Chenxiong , Feuer Eric J. 
Published: May 2003

AbstractWe propose an estimator of the probability of developing a disease in a given age range, conditional on never having developed the disease prior to the beginning of the age range. Our estimator improves the one described by Wun, Merrill and Feuer ( Lifetime Data Analysis 1998; 4, 169–186) that is currently used by the U.S. National Cancer Institute for the SEER Cancer Statistics Review. Both estimators use cross‐sectional disease rates and provide an interpretation of these rates in terms of the age‐conditional probability of developing disease in a hypothetical cohort. The difficulty of this problem is that rates are not available per person‐years alive and disease free, but only per person‐years alive. Wun et al. used ad hoc methods to handle this problem which did not properly account for competing risks, did not provide a measure of variability, and only allowed age ranges using prespecified 5‐year age intervals. Here we solve the problem under a unified competing risks framework, which allows the calculation of the age‐conditional probabilities for any age range. We generalize gamma confidence intervals to apply to our new statistic. Although our new method provides estimates which are numerically similar to that of Wun et al., this paper provides a comprehensive theoretical basis for estimation and inference about the age‐conditional probability of developing a disease. Published in 2003 by John Wiley & Sons, Ltd.
A maximum likelihood approach for estimating the QT correction factor using mixed effects model
Authors: Shah Amrik , Hajian Gerald 
Published: May 2003

AbstractAssessment of QT interval prolongation is often used for assessing the cardiac safety of a new drug. However, the correction of the QT interval for varying heart rates has potential bias due to various different correction factors. This article proposes a maximum likelihood (ML) approach for calculating the appropriate individual correction factor using the data. The data come from a study with 24 subjects participating in a 10 day multiple dose (NEW RX) placebo‐controlled cross‐over trial with repeat ECGs obtained at baseline and at day 10. ML techniques were used to fit a random‐effects model to observed QT and HR values for estimating the pooled and individual correction factors. QTc values using four correction factors (Bazett, Friderecia, pooled and individual) were investigated. The relative performance of the various correction factors are given in terms of variability and graphical techniques. The pooled correction factor was estimated to be 0.292 and the individual correction factors ranged from 0.19 to 0.41. The assessment of the treatment effect on QTc yielded inconsistent results. Bazett's factor indicated prolongation (6.55±1.20), Friderecia's factor indicated no change, while the pooled (‐2.92±0.94) and individual (‐2.82±1.00) factors showed a significant decrease. Graphical examination of individual QTc data showed a significant advantage in the use of individual correction factors versus Bazett's factor both in terms of sensitivity as well as reduction in bias. Use of individual correction factors is advocated for the assessment of possible drug‐induced QTc prolongation. Copyright © 2003 John Wiley & Sons, Ltd.
Interval estimates of the probability of toxicity at the maximum tolerated dose for small samples
Authors: Natarajan Loki , O'Quigley John 
Published: May 2003

AbstractFollowing on from the work of O'Quigley et al., we investigate the performance of interval estimates of the probability of toxicity following completion of a phase I clinical trial. Our particular focus is on very small sample sizes, not uncommon in phase I studies. Specifically, we study the situations for which the sample sizes are 12 or 16. Simulations are used to show that the coverage of the confidence intervals, even for very modest sample sizes, are close to nominal in most cases. Averaged over the range of situations considered, coverage rates are accurate for both sample sizes of 12 and 16. As for the larger sample size of 20, studied previously, it is possible to obtain further, albeit modest, improvements via the use of the Cornish–Fisher inversion. Copyright © 2003 John Wiley & Sons, Ltd.
Robustness of sample size re‐estimation procedure in clinical trials (arbitrary populations)
Authors: Govindarajulu Z. 
Published: May 2003

AbstractIn clinical trials, one of the main questions that is being asked is how many additional observations, if any, are needed beyond those originally planned. In a two‐treatment double‐blind clinical experiment, one is interested in testing the null hypothesis of equality of the means against one‐sided alternative when the common variance σ2 is unknown. We wish to determine the required total sample size when the error probabilities αand βare specified at a predetermined alternative. Shih provided a two‐stage procedure which is an extension of Stein's one‐sample procedure, assuming normal response. He estimates σ2 by the method of maximum likelihood via the EM algorithm and carries out a simulation study in order to evaluate the effective level of significance and the power. The author proposed a closed‐form estimator for σ2 and showed analytically that the difference between the effective and nominal levels of significance is negligible and that the power exceeds 1‐β when the initial sample size is large. Here we consider responses from arbitrary distributions in which the mean and the variance are not functionally related and show that when the initial sample size is large, the conclusions drawn previously by the author still hold. The effective coverage probability of a fixed‐width interval is also evaluated. Proofs of certain assertions are deferred to the Appendix. Copyright © 2003 John Wiley & Sons, Ltd.
Developmental dynamics in L1 and L2 acquisition: Processability Theory and generative entrenchment
Authors: PIENEMANN MANFRED 
Published: May 2003

This paper has two major objectives: (1) to summarise Processability Theory, a processing-oriented approach to explaining language development and (2) to utilise this theory in the comparison of development in LI and L2 acquisition. Proponents of the Fundamental Difference Hypothesis (between L1 and L2) assume that L1 development can be explained with reference to Universal Grammar (UG) which, in their view, is inaccessible to L2 learners. Instead, they claim that a second language develops on the basis of language processing strategies.I will show that the fundamentally different developmental paths inherent in first and second language acquisition can both be explained on the basis of the same language processing mechanics (as specified in Processability Theory). I will demonstrate that the developmental differences between L1 and L2 are caused by the qualitatively different early structural hypotheses which propagate through the acquisition process. The concept of “propagation of structural features” will be viewed as “generative entrenchment,” a logical-mathematical concept, which has proved to be highly productive in examining other kinds of developmental processes.
Comparing and explaining the trajectories of first and second language acquisition: in search of the right mix of psychological and linguistic factors
Authors: KEMPEN GERARD 
Published: May 2003

When you compare the behavior of two different age groups which are trying to master the
same sensori-motor or cognitive skill, you are likely to discover varying learning routes:
different stages, different intervals between stages, or even different orderings of stages.
Such heterogeneous learning trajectories may be caused by at least six different types of factors:(1) Initial state: the kinds and levels of skills the learners have available at the onset of the learning episode.(2) Learning mechanisms: rule-based, inductive, connectionist, parameter setting, and so on.(3) Input and feedback characteristics: learning stimuli, information about success and failure.(4) Information processing mechanisms: capacity limitations, attentional biases, response preferences.(5) Energetic variables: motivation, emotional reactions.(6) Final state: the fine-structure of kinds and levels of subskills at the end of the learning episode.This applies to language acquisition as well. First and second language learners probably differ on all six factors. Nevertheless, the debate between advocates and opponents of the Fundamental Difference Hypothesis concerning L1 and L2 acquisition have looked almost exclusively at the first two factors. Those who believe that L1 learners have access to Universal Grammar whereas L2 learners rely on language processing strategies, postulate different learning mechanisms (UG parameter setting in L1, more general inductive strategies in L2 learning). Pienemann opposes this view and, based on his Processability Theory, argues that L1 and L2 learners start out from different initial states: they come to the grammar learning task with different structural hypotheses (SOV versus SVO as basic word order of German).
Attitudes toward psychiatry among students entering medical school
Authors: Malhi G. S. , Parker G. B. , Parker K. , Carr V. J. , Kirkby K. C. , Yellowlees P. , Boyce P. , Tonge B. 
Published: May 2003

Objective:  To survey the attitudes of Australian medical students to determine their views about the relative attractiveness of psychiatry as a career compared with other specialities, and against findings from a North American study.Method:  We surveyed 655 first‐year medical students attending six Australian Universities.Results:  Responses indicated that Australian medical students view psychiatry as distinctly less ‘attractive’ than other career options, as reported in the North American sample. In comparison with other disciplines, psychiatry was regarded as more interesting and intellectually challenging, but also as lacking a scientific foundation, not being enjoyable and failing to draw on training experiences.Conclusion:  Our findings suggest that psychiatry has an image problem that is widespread, reflecting community perceptions and the specialist interests of medical students on recruitment. If psychiatry is to improve its ‘attractiveness’ as a career option, identified image problems need to be corrected and medical student selection processes re‐considered.
A follow‐up study of juvenile obsessive–compulsive disorder from India
Authors: Janardhan Reddy Y. C. , Srinath S. , Prakash H. M. , Girimaji S. C. , Sheshadri S. P. , Khanna S. , Subbakrishna D. K. 
Published: May 2003

Objective:  To study the long‐term course and outcome of juvenile obsessive–compulsive disorder (OCD).Method:  Two to 9‐year follow‐up of largely self‐referred, drug‐naïve subjects (n = 58) by employing catch‐up longitudinal design.Results:  The mean follow‐up period was 5 years. Nearly three‐fourth of the sample was adequately treated with medications. Only 21% of the subjects had clinical OCD at follow‐up and 48% were in true remission (no OCD and not on treatment). Earlier age‐at‐onset was associated with better course and outcome.Conclusion:  Juvenile OCD has favorable outcome. Our findings are applicable to psychiatric hospital settings in India and perhaps to the general psychiatric settings in the Western countries. Whether the better outcome in this sample is the result of differing clinical characteristics or because of true cross‐cultural variation in the course needs further exploration. It is speculated that early onset OCD could be a subtype of juvenile OCD with better outcome.
A case study of an extremely violent serial rapist with borderline personality disorder in remission
Authors: Martens W. H. J. 
Published: May 2003

Objective:  To provide evidence that some borderline patients with poor prognosis can obtain complete remission.Method:  Case of a violent rapist with borderline personality disorder in remission is reported. An attempt was made to reveal the mechanism of recovery in this forensic patient who initially was assessed as psychotherapeutically untreatable.Results:  Psychotherapeutic effects and favourable psychosocial factors such as successful college graduation, increased social–emotional capacities and valuable new relationships did also play a very important role in this remission process.Conclusion:  Controlled studies are necessary to elucidate the mechanism of recovery among criminal patients with borderline personality disorder in order to provide adequate treatment programmes and to construct more reliable prediction methods for prognosis and reoffending.
Shared decision making in psychiatry
Authors: Hamann J. , Leucht S. , Kissling W. 
Published: May 2003

Objective: In other medical fields, ‘shared decision making’ (a strategy for including patients in therapeutic decision processes) has been studied for several years now. This survey presents the potential of shared decision making for psychiatry.Method: Literature search.Results: Research in other medical fields shows that shared decision making positively influences patients’ satisfaction as well as health outcomes. The application of shared decision making to psychiatry is still in the initial stage.Conclusion: Evidence that shared decision making can be successfully practiced in psychiatry would contribute to an improved inclusion of psychiatric patients in therapeutic decisions and thereby help to implement basic rights of a group of patients who have not sufficiently benefited from consumer empowerment in other medical fields.
Can presence or absence of periodontal pathogens distinguish between subjects with chronic and aggressive periodontitis? A systematic review
Authors: Mombelli Andrea , Casagni Federico , Madianos Phoebus N. 
Published: May 2003

AbstractObjectives:  The purpose of this study was to determine to what extent the presence or absence of periodontal pathogens can distinguish between subjects with chronic and aggressive periodontitis.Material and Methods:  A systematic review of cross sectional and longitudinal studies providing microbiological data both from patients with chronic periodontitis (ChP) and aggressive periodontitis (AgP) at a subject level. Strict inclusion criteria were applied. The presence or absence of five microorganisms was selected as primary study parameters: Actinobacillus actinomycetemcomitans (AA), Porphyromonas gingivalis (PG), Prevotella intermedia (PI), Bacteroides forsythus (BF), and Campylobacter rectus (CR).Results:  The presence or absence of AA could be evaluated in 11 papers. In seven papers the presence or absence of PG could be analysed. Subject specific data on PI were available from six studies. Two studies could be used regarding the presence or absence of BF, and two regarding CR. Sensitivity and specificity of every microbiological test were individually calculated for each selected study, assuming that the clinical diagnosis of AgP or ChP was the true status the tests attempted to detect. AgP was considered to be the condition of interest and ChP was considered equivalent to ‘non‐AgP’. Receiver Operator Characteristic (ROC) diagrams were constructed using these data. ROC diagrams indicated the limited discriminatory ability of all of the test parameters to identify subjects with AgP. An additional assessment showed that the highly leukotoxic variant of AA was uniquely associated with patients suffering from aggressive periodontitis. However, in a high proportion of patients diagnosed with AgP the presence of this variant could not be detected.Conclusion:  The presence or absence of AA, PG, PI, BF or CR could not discriminate between subjects with AgP from those with ChP.
A systematic review of the effect of anti‐infective therapy in the treatment of peri‐implantitis
Authors: Klinge Björn , Gustafsson Anders , Berglundh Tord 
Published: May 2003

AbstractThe aim of this systematic review was to assess the treatment of peri‐implantitis with special emphasis on the role of anti‐infective therapy. No randomized controlled clinical trial was available for analysis. Of 145 peri‐implant studies initially screened, 21 studies (six human and 15 animal studies) were analysed regarding the outcome of treatment of peri‐implantitis. A multitude of treatment regimens, including anti‐infective therapy, was reported. The antibiotic regimens varied between studies. No standardized medication protocol was used. Type of antibiotic, dosage, duration and time for initiation of antibiotic treatment were different for all studies, but details were not always reported. A non‐medicated control group was reported in one animal experiment only. The outcomes following anti‐infective treatment of peri‐implantitis are highly variable. The evidence for a consistent and clinically relevant advantage using antibiotics can be questioned in this context. There are to date no data available to support specific treatment protocols. It is suggested that randomized human controlled clinical trials for the treatment of peri‐implantitis be initiated.
A systematic review of the survival of implants in bone sites augmented with barrier membranes (guided bone regeneration) in partially edentulous patients
Authors: Hämmerle Christoph H. F. , Jung Ronald E. , Feloutzis Andreas 
Published: May 2003

AbstractThe aim of the present systematic review was to assess the survival of implants in regenerated bone applying the method of guided bone regeneration (GBR) compared with the survival of implants in non‐regenerated bone. Studies to be included in this review needed to provide at least 12‐month results following prosthetic reconstruction of titanium implants in bone regenerated by GBR with or without membrane supporting materials. The outcome measures were implant survival described as presence of implant, implant success (according to the criteria in the respective study), absence of clinical implant mobility, absence of implant fracture, absence of progressive peri‐implant crestal bone loss as assessed on radiographs without clinical signs of peri‐implant infection, absence of peri‐implant infection with suppuration. A MEDLINE search and a hand search of relevant scientific journals were conducted including studies from the year 1990 to May 2001. A total of 11 studies could be identified fulfilling the inclusion criteria. All studies except two had the characteristics of case series or cross‐sectional surveys. The two different studies had both test and control implants included in their analysis and qualified as controlled clinical trials. Cumulative success or survival rates, respectively, for implants in regenerated bone ranged from 100% after 5 years to 79.4% after 5 years of function. Regarding survival data, no significant differences were found in the controlled clinical trials between implants in regenerated compared to implants in non‐regenerated bone. Within the limits of this systematic review characterized by second and third levels of evidence, the following conclusions can be drawn: The survival rate of implants placed into sites with regenerated/augmented bone using barrier membranes varied between 79% and 100% with the majority of studies indicating more than 90% after at least one year of function. The survival rates obtained in the present systematic review are similar to those generally reported for implants placed conventionally into sites without the need for bone augmentation.
A guide to systematic reviews
Authors: Needleman Ian G. 
Published: May 2003

AbstractSystematic reviews have become widely used for evaluating evidence across all fields of biomedicine. The objective of a systematic review is to provide a comprehensive and contemporary appraisal of research using transparent methods whilst aiming to minimize bias. In essence, research methodology is employed in the conduct of the review. Such reviews are therefore fundamentally different from traditional ‘narrative’ review articles in their purpose and in their potential to aid clinical decision‐making. This paper is a guide to the rationale and nature of systematic reviews and will provide a background to understanding their use in clinical practice.