Modified Larsen scoring of digitized radiographs in rheumatoid arthritis

OBJECTIVE: To facilitate storage, retrieval, and analysis of radiographic images we assessed the validity of a film digitizer and computer based system. METHODS: A total of 101 sets of radiographs of hands and feet from patients with early rheumatoid arthritis were digitized according to standards defined by the American College of Radiology. Two blinded observers applied the modified Larsen score to the digitized images and the original radiographs. RESULTS: There was good concordance between the scoring of digitized images and radiographic films; intraclass correlation coefficient was 0.89. Regression analysis of a Bland-Altman plot revealed that there was no significant systematic bias. It was noted that scoring the digital images took more than twice as long as scoring the radiographic films. CONCLUSION: Our results indicate that modified Larsen scoring of adequately digitized films on standard computer displays is valid and shows good agreement with conventional techniques. Scoring digitized images appears to require more time, but this may be outweighed by the considerable advantages of computer storage and retrieval of radiographic images.     

Pragmatic controlled clinical trials in primary care: the struggle between external and internal validity

Background  

Controlled clinical trials of health care interventions are either explanatory or pragmatic. Explanatory trials test whether an intervention is efficacious; that is, whether it can have a beneficial effect in an ideal situation. Pragmatic trials measure effectiveness; they measure the degree of beneficial effect in real clinical practice. In pragmatic trials, a balance between external validity (generalizability of the results) and internal validity (reliability or accuracy of the results) needs to be achieved. The explanatory trial seeks to maximize the internal validity by assuring rigorous control of all variables other than the intervention. The pragmatic trial seeks to maximize external validity to ensure that the results can be generalized. However the danger of pragmatic trials is that internal validity may be overly compromised in the effort to ensure generalizability. We are conducting two pragmatic randomized controlled trials on interventions in the management of hypertension in primary care. We describe the design of the trials and the steps taken to deal with the competing demands of external and internal validity.     

In vitro fatigue behavior of human dentin with implications for life prediction

Although human dentin is known to be susceptible to failure under repetitive cyclic fatigue loading, there are few reports in the literature that reliably quantify this phenomenon. This study seeks to address the paucity of fatigue data through a systematic investigation of the effects of prolonged cyclical loading on human dentin in an environment of ambient temperature Hank's balanced salt solution (HBSS) at cyclic frequencies of 2 and 20 Hz. The "stress-life" (S/N) data thus obtained are discussed in the context of possible mechanisms of fatigue damage and failure in this material. In addition, stiffness loss data collected in situ during the S/N tests are used to deduce crack velocities and the thresholds for such cracking. These results are presented in a fracture mechanics context as plots of fatigue-crack propagation rates (da/dN) as a function of the stress-intensity range (Delta K). Such S/N and da/dN-Delta K data are discussed in light of the development of a framework for a fracture-mechanics-based methodology for the prediction of the fatigue life of teeth. It is concluded that the presence of small (on the order of 250 microm) incipient flaws in human teeth will not radically affect their useful life.     

Review of economic evaluations of radiofrequency catheter ablation for cardiac arrhythmias

A systematic review of current studies on the cost effectiveness of catheter ablation for treatment of tachycardia in adults was undertaken. The results are summarized based on a predefined framework of principles for economic evaluation. Of 192 abstracts identified, only three cost effectiveness studies were identified. Each focused on a different and specific patient group with selected target disorders, and used decision analysis modelling to estimate cost effectiveness. Radiofrequency catheter ablation is likely to be economically attractive compared with drug therapy in adult patients with frequently symptomatic paroxysmal supraventricular tachycardia (radiofrequency catheter ablation dominates drug therapy options) or in ventricular tachycardia patients with pre-existing ischemic coronary disease (cost effectiveness ratio of about US $21,000 per quality adjusted life year), but not in the treatment of asymptomatic Wolff-Parkinson-White syndrome patients. However, these studies evaluated different types of tachycardias in differing patient populations and all are based on United States data, so decision-makers must be cautious when applying these results to a general population with tachycardia in the Canadian context.     

Transitions in health status in older patients with heart failure

BACKGROUND: We aimed to determine transitions in health perception and functional status in older Medicare patients with heart failure. METHODS: We used 1991 to 1994 data from the Medicare Current Beneficiary Survey, a database that combines Medicare claims with yearly longitudinal surveys. We identified 872 patients 65 years or older in 1991 with a diagnostic code of heart failure. RESULTS: At baseline, 58% of the patients rated their general health perception as "fair" or "poor." Over 1 year, 18% of the patients died. Transition matrices revealed that health perception, activities of daily living, and instrumental activities of daily living were strong correlates of mortality; that dramatic changes in health status were relatively uncommon over 1 year among survivors; and that decline was common in patients with "excellent" or "very good" health perception. The prior year's health status and comorbidity were powerful predictors of the subsequent year's health status. CONCLUSION: Many older patients with heart failure have worsening health status over time. Measures of prior health status can help predict chances of functional recovery.     

Molecular cloning of a vaccine antigen against infection with the larval stage of Echinococcus multilocularis

Alveolar and cystic hydatidosis are caused by infection with the larval stages of Echinococcus multilocularis and Echinococcus granulosus, respectively. A host-protective antigen has been identified in E. granulosus. Here we identify the presence of a closely related protein in E. multilocularis, characterize and express a cDNA encoding the antigen (designated EM95), determine the structure of the em95 gene, and demonstrate that the EM95 recombinant protein can be used to induce significant levels of protection against challenge infection with E. multilocularis eggs in mice.     

A risk-factor model of epistatic interaction,focusing on autism

Research to date on the genetics of autism has not uncovered a major susceptibility locus and indications are that a number of genes, perhaps as many as 15-20, may play detectable but minor roles in the etiology of the condition. To cope with this situation, a risk-factor model based on standard epidemiologic designs is proposed. The model supposes that adding a factor to a fixed set of existing factors always increases the total risk. Thus, according to the model genetic contributions cumulate but are not necessarily additive. A threshold, hence, epistasis is required. The model is applied to several conditions in which the risk of autism is elevated, some genetic (fragile X, tuberous sclerosis) and some exogenous (rubella and thalidomide embryopathies). Male gender is discussed as a risk factor. This approach is contrasted primarily with Gillberg and Coleman's view of autism as "a syndrome or series of syndromes caused by many different separate individual diseases." The principal point of difference is whether the effects of different causes cumulate or do not cumulate. In the present approach they do, in Gillberg and Coleman's they do not.     

Providing a healthcare input to children in special schools

The education of children with special educational needs is often accompanied by a requirement for medical or healthcare provision. If this cannot be done safely then the child's access to education is limited. No standardized template for the delivery of a healthcare input to children in special schools is apparent. This study sought to explore, through the use of an indepth needs assessment exercise and focus group interviews, what the most appropriate healthcare role was for delivering health care in a special school catering for children with a broad range of severe learning disabilities. While an overwhelming viewpoint of participants in focus groups perceived that a nurse was the only suitable person to undertake the role, the evidence gathered prompted the research steering group to suggest to the contrary, i.e. that the role of a healthcare worker with a national vocational qualification (NVQ) level 3 in care was the more appropriate person to maximize both the role of the nurse and the quality of care provided to these children.     

Measurement of endotoxin activity in critically ill patients using whole blood neutrophil dependent chemiluminescence

Background  

Lipopolysaccharide (endotoxin) from the cell wall of Gram-negative bacteria is a potent trigger for the release of host-derived inflammatory mediators. The relationship between endotoxaemia, Gram-negative infection and the clinical syndrome of sepsis has been difficult to establish, in part because of the limitations of available endotoxin assays.