Group designs in clinical research

Single-subject research designs, with their concentration on the individual subject over extended time durations, are similar in form to the design of therapy and have been represented as the best, if not the only, appropriate method for carrying out clinical research. Despite the similarity between single-subject research sessions and clinical sessions, it is argued that such designs are not intrinsically more appropriate than group designs for clinical research. Single-subject and group research strategies are alternative and often competing approaches to the same research question, and the choice resides as much in the predilections of the researcher as in any intrinsic advantage in one or the other research strategy.     

Tutorial: application of regression analysis concepts to retrospective research in speech pathology.

The underlying logic of retrospective research in speech pathology is examined critically. This research model focuses on differences among discrete groups. Regression analysis concepts are suggested as a tool to evaluate the practical or theoretical importance of statistically significant differences obtained in retrospective research. This type of analysis focuses on the degree to which a criterion measure can be predicted from knowledge of group classification, rather than on differences among means.     

Tutorials in clinical research: part IV: recognizing and controlling bias.

OBJECTIVE: This is the fourth of a series of Tutorials in Clinical Research (1-3). The objectives of this article are to heighten reader awareness of biases and of methods to reduce their impact and to provide an easy reference document for the reader during future journal reading. STUDY DESIGN: Tutorial. METHODS: The authors met weekly for 4 months discussing clinical research articles and biases for which they might be at risk. Liberal use of reference texts and specific articles on bias were reviewed. Like the example by Sackett, biases were catalogued to create an easily understood reference. Articles were chosen to demonstrate how understanding bias might facilitate assessment of the validity of medical publications. RESULTS: The article is organized into three main sections. The first section introduces specific biases. Two tables serve as rapid reference tools. The second section describes the most common biases linked to specific research approaches and reviews techniques to minimize them. The last section demonstrates the application of the information to an article in a manner that can be applied to any article. CONCLUSIONS: Assessing the validity of a medical publication requires an awareness of bias for which the research is inherently at risk. A review of the publication to determine what steps the authors did or did not undertake to minimize the impact of biases on their results and conclusions helps establish the validity. This article should be of assistance in this critical review task.     

Limitations of analysis of covariance designs in aging research

Control of peripheral hearing loss represents a significant design problem in research examining age-related changes in central auditory processing. Statistical control procedures (e.g., partial correlation or analysis of covariance) represent one means of achieving such experimental control. Although these techniques have been advocated for this purpose by some researchers, potential confounding of the data due to statistical dependence between age and peripheral hearing loss may introduce significant bias into the data distorting the reported results.     

Some issues in the statistical analysis of completely randomized and repeated measures designs for speech, language, and hearing research.

Contemporary investigators in the areas of speech, language, and hearing rely heavily on inferential statistical procedures to answer both basic and applied research questions. Such statistical procedures typically involve a number of assumptions that need to be fulfilled in order for the procedure to be appropriate for a specific data set. Unfortunately, a review of recent publications in the Journal of Speech, Language, and Hearing Research indicated that some pivotal issues related to those underlying assumptions, although widely discussed and emphasized in the statistical literature, often appear to be neglected in these fields of research. This tutorial therefore addresses two issues that are particularly important for an appropriate and accurate use of some of the most commonly used statistical procedures. The first issue concerns the importance of addressing the sphericity assumption in studies with a repeated measures design. The second issue concerns the definition of the experimental units in a statistical analysis and applies to both completely randomized and repeated measures designs. Theoretical aspects associated with each issue are discussed, and appropriate strategies for data entry and analysis are presented.     

Flexibility of single-subject experimental designs. Part I: Review of the basics of single-subject designs

The discussion in this article is directed at a brief review of the basic components of single-subject experimental designs. It sets out to present some of the technical and practical advantages in developing single-subject designs to evaluate potential treatment variables and treatments. The point is made that the designs are specifically structured for applied, intervention research. In addition to explaining how the basic AB components function to allow for a controlled evaluation, a short review is included of other factors important to the scientific method such as operational definitions, reliability, repeated measures, and internal and external validity. The article serves as a foundation for the following two articles that are directed at demonstrating the flexibility of single-subject experimental studies.     

Use of mean morphological units to assess language development.

The intent of this study was to determine what size language sample was needed in order to obtain a reliable index of mean morphological units. Shriner (1967) suggested that 50 sentences were necessary for obtaining a mean length of response and a length complexity index. Brown (1973) recommended using 100 sentences when determining mean morphological units. However, other investigators (Schneiderman, 1955; Griffith and Miner, 1969) said that as few as 15 sentences could serve to provide enough data for reliable estimates of mean length of response and a length complexity index. For a practitioner, knowing that the first 15 sentences produced would be a reliable estimate of overall language ability would be of substantial benefit. Obtaining, transcribing, and analyzing 15 sentences takes about 20 min. The results of this study show that as few as 15 sentences are adequate for determining a reliable index of mean morphological units.     

Augmentative communication systems taught to cerebral-palsied children--a longitudinal study. III. Teaching practices and exposure to sign and symbol use in schools and homes.

A longitudinal study of augmentative communication training with 40 language-impaired, cerebral-palsied children examined the teaching practices adopted in schools, and the extent to which teachers and parents used the augmentative systems with the children. The study found limited exposure to sign and symbol training in formal teaching sessions and in other school settings, and teachers made relatively few attempts to foster spontaneous use of the systems and generalisation outside of formal training settings. Exposure to augmentative communication in the children's homes was equally limited, and a significant number of parents expressed reservations about the value of the systems for their children. These findings may at least partly account for the children's limited progress in sign and symbol acquisition and use over an 18-month period, which was documented in two earlier reports.     

梅尼埃病的听-前庭功能诊断的Logistic回归分析

目的:采用多指标的Logistic回归分析方法探讨梅尼埃病临床特征及耳蜗与前庭功能损害的特征.方法:36例梅尼埃病患者和30例其他外周性眩晕对照组进行临床资料分析,完成纯音测听、Metz重振测试、耳蜗电图、甘油试验、ABR等听力学检查以及双温试验、摇头眼震试验、Fukuda踏步试验.对临床体征、耳蜗与前庭功能检查的各项指标进行单因素χ2 分析,然后进行多因素Logistic回归分析.结果:①波动性听力下降、四联征出现的个数、Tullio现象、耳蜗电图-SP/AP幅值比、Metz重振试验、甘油试验在梅尼埃组与非梅尼埃组间差异有统计学意义(P<0.05);②建立了以耳蜗电图(X1)、甘油试验(X2)、症状的个数(X3)、波动性听力下降(X4)为变量的梅尼埃病Logistic回归预测方程:Logit(p)=-9.443+3.110 X1 +5.015X2 +2.506 X3 +3.963 X4.Logistic模型预报正确率为95.5%,ROC曲线下面积为0.993.结论:梅尼埃病的临床表现特征性明显,配合耳蜗-前庭功能的客观检查,可与其他外周性眩晕相鉴别,相关因素的Logistic回归预测方程可对梅尼埃病进行辅助诊断.     

Solitary infantile myofibromatosis in the lateral orbit floor showing spontaneous regression.

Infantile myofibromatosis is a rare benign tumour usually occurring early in infancy. We describe the case of a 10-year-old boy with solitary infantile myofibromatosis in the left lateral orbit floor which regressed spontaneously. Although our patient was older than previously reported cases and showed bony destruction confirmed by computed tomography (CT), this tumour was diagnosed as infantile myofibromatosis based on immunohistochemical findings. The tumour disappeared spontaneously six months after incisional biopsy, that also indicated this tumour was an infantile myofibromatosis.     

Cranial base hemorrhage. A technique for controlling the uncontrollable

In the management of trauma, control of life-threatening hemorrhage must be accomplished expeditiously if morbidity is to be decreased and mortality prevented. Hemorrhage from the inaccessible cranial base, especially when transected vessel stumps are not available for direct control, can be the most demanding, life-threatening, surgical emergency. We present our experience in utilizing an autologous bone grafting technique to successfully control severe hemorrhage from the base of the skull. In our review of the literature to date, we have been unable to ascertain whether this modality has been previously used.     

Augmentative communication systems taught to cerebral-palsied children--a longitudinal study. II. Pragmatic features of sign and symbol use.

Pragmatic analysis of the sign and symbol utterances produced by 40 language-impaired, cerebral-palsied children in semi-structured conversational settings revealed severe restrictions in the range of communicative functions that were used. The children were able to communicate certain conversational acts effectively, but over 80% of all utterances expressed just four communicative functions. There were also some significant gaps, with certain functions not being used at all. The children's progress was followed up at 6-month intervals over a period of 1 1/2 years. Few changes were found in the range and relative frequencies of communicative functions expressed over time. There were few significant differences between the symbol and sign users on these measures, which suggests that overall neither augmentative mode facilitated greater communicative use than the other.     

Translational research in aphasia: from neuroscience to neurorehabilitation.

PURPOSE: In this article, the authors encapsulate discussions of the Language Work Group that took place as part of the Workshop in Plasticity/NeuroRehabilitation Research at the University of Florida in April 2005. METHOD: In this narrative review, they define neuroplasticity and review studies that demonstrate neural changes associated with aphasia recovery and treatment. The authors then summarize basic science evidence from animals, human cognition, and computational neuroscience that is relevant to aphasia treatment research. They then turn to the aphasia treatment literature in which evidence exists to support several of the neuroscience principles. CONCLUSION: Despite the extant aphasia treatment literature, many questions remain regarding how neuroscience principles can be manipulated to maximize aphasia recovery and treatment. They propose a framework, incorporating some of these principles, that may serve as a potential roadmap for future investigations of aphasia treatment and recovery. In addition to translational investigations from basic to clinical science, the authors propose several areas in which translation can occur from clinical to basic science to contribute to the fundamental knowledge base of neurorehabilitation. This article is intended to reinvigorate interest in delineating the factors influencing successful recovery from aphasia through basic, translational, and clinical research.     

Flexibility of single-subject experimental designs. Part III: Using flexibility to design or modify experiments

The purpose of this paper is to present clinical researchers with viable alternatives to basic, prototypical single-subject experimental designs. The availability of these alternatives is a product of the flexibility inherent in the application of these designs. Two general types of flexibility are discussed: a priori flexibility, as in combining designs in one study and ad hoc flexibility in which a design is modified during the course of a study. The flexibility afforded by the designs provides the opportunity to fashion individual experimental designs for specific research problems addressed. A review of the clinical research literature published during the last 10 years revealed that the flexibility of these designs has been underutilized. The benefits that can derive from using the potential flexibility of the designs are described, and specific suggestions are made for incorporating flexibility into clinical research.     

The prooxidant system. Approaches to the choice of research algorithm

The regulatory function of the processes involving free radicals known to maintain cellular vital activity and their role as an intermediate stage of many vitally important enzymatic reactions attract the attention of researchers interested in the mechanisms of production and inactivation of free radicals. Investigations into prooxidant and antioxidant systems along with evaluation of the intensity of free-radical oxidation make it possible to resolve many problems including elucidation of dynamic activity of pathological process, prognosis of various pathological conditions, and the choice of possible methods for the correction of prooxidant/antioxidant balance in patients with ENT diseases. The development of algorithms and methods for the assessment of parameters of activity of the prooxidant system allows for their stage by stage measurement and evaluation.