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Biomedical subjects

R A Fox

Publications and source records attributed to R A Fox.

At least 19 recordsLinked to original sources
PubMed2006

Rituximab for adolescents with haemophilia and high titre inhibitors.

Neutralizing alloantibodies (inhibitors) to factor VIII or factor IX develop in approximately 25% of patients with haemophilia A and <3% of patients with haemophilia B treated with factor concentrate. Patients with high titre inhibitors, in whom immune tolerance therapy fails, have few treatment options. Targeted anti-B-cell therapy with rituximab (chimeric anti-CD20) has been useful in several antibody-mediated autoimmune states. Case reports of rituximab treatment in small numbers of haemophilia patients with inhibitors have been inconclusive. We describe three adolescent patients with severe haemophilia and inhibitors treated with four weekly doses of rituximab, 375 mg m(-2). Treatment with rituximab was effective in reducing the inhibitor titre in two of three patients. Rituximab may be beneficial for patients with severe haemophilia and inhibitors in whom standard therapies have failed, but larger prospective studies are required to determine safety, efficacy and predictors of success.

Adolescent↗
PubMed2002

Intravascular brachytherapy of the coronary arteries.

This is a review of the relatively recently developed field of intravascular brachytherapy of coronary arteries. It presents a brief overview of the discipline of coronary angioplasty describing the problem of restenosis and discusses the potential for ionizing radiation to overcome this problem. It examines the various methods that have been used to irradiate the coronary arteries comparing their advantages and disadvantages. Special consideration is given to seeds and wires in the artery, radioactive liquids in the angioplasty balloon and radioactive stents. Passing reference is made to a number of other methods that have also been proposed, but which are not commonly used to irradiate the coronary arteries at present. The dosimetry of each of the major techniques is discussed and the data from different laboratories compared. Specific consideration is given to the need for centring of the radioactive source and the factors affecting the selection of a dose prescription. A brief review of recent clinical trials is followed by an examination of possible future directions in this field including the use of intravascular ultrasound to improve dosimetry, the use of gas-filled balloons to enhance the penetration of beta-emitting sources and the use of gamma-emitting stents to overcome the problems associated with edge restenosis.

Angioplasty, Balloon↗
PubMed2001

Neurological evidence in support of a specialized phonetic processing module.

Event-related potentials (ERPs) were utilized to study brain activity while subjects listened to speech and nonspeech stimuli. The effect of duplex perception was exploited, in which listeners perceive formant transitions that are isolated as nonspeech "chirps," but perceive formant transitions that are embedded in synthetic syllables as unique linguistic events with no chirp-like sounds heard at all (Mattingly et al., 1971). Brain ERPs were recorded while subjects listened to and silently identified plain speech-only tokens, duplex tokens, and tone glides (perceived as "chirps" by listeners). A highly controlled set of stimuli was developed that represented equivalent speech and nonspeech stimulus tokens such that the differences were limited to a single acoustic parameter: amplitude. The acoustic elements were matched in terms of number and frequency of components. Results indicated that the neural activity in response to the stimuli was different for different stimulus types. Duplex tokens had significantly longer latencies than the pure speech tokens. The data are consistent with the contention of separate modules for phonetic and auditory stimuli.

Adult↗
PubMed2001

Proposal for a gamma-emitting stent for the prevention and treatment of coronary artery restenosis.

Radioactive stents have failed to prevent restenosis despite the demonstrated success of other radionuclide therapies using beta- or gamma-emitting radionuclides in the coronary arteries. This may be due to the rapid dose reduction at the end of the stent that occurs with a stent coated with 32P, which is a pure beta-emitter. A gamma-emitter will give a greater dose beyond the end of the stent and would therefore be expected to produce better results. However, it is essential that the gamma-emitter is not contaminated with beta particles of either sign nor with conversion electrons. This requirement generally demands the use of a high energy gamma-emitter, preferably with an energy greater than 500 keV. High energy gammas have other advantages, including a high radiation dose delivered per decay which reduces the total activity required and reduced dose near to the source due to electron disequilibrium. The ideal dose distribution is one that provides a uniform dose to the proliferating tissues and a reduced dose elsewhere. Although the target tissues are not well defined it is believed that the adventitia is the source of the proliferating cells. Hence the target tissue is between 0.5 and 2 mm depth into the artery. It is shown that 96Tc is a very suitable radionuclide for the production of radioactive stents giving a significantly greater dose compared with 32P both at depth and beyond the end of the stent for the same dose at the surface of the stent. Furthermore, 96Tc should be able to be made with a standard medical cyclotron and may be coated on to a stainless steel stent by a simple process that takes approximately 30 minutes to perform. Its half-life of 4.3 days will allow radioactive stents to be transported over significant distances and will result in a treatment time with a mean value of approximately 1 week. This will allow the rapid reestablishment of the endothelial layer which may be a further advantage of this radioactive stent.

Angioplasty, Balloon, Coronary↗
PubMed2001

The use of 188Re to treat in-stent re-stenosis of coronary arteries.

A pilot study has been conducted in which coronary arteries subject to re-stenosis after angioplasty and stenting have been irradiated following further angioplasty. The method of irradiation has been to use radioactive 188Re in an angioplasty balloon. This paper considers all aspects of the procedure including elution of the rhenium from a tungsten/rhenium generator, its concentration, dispensing and safe delivery to the patient using specially designed equipment to reduce staff doses and radioactive spills. In the pilot study of 28 lesions in 26 patients only 1 was recorded as having angiographic re-stenosis in the treated region at 6 months although 4 other patients had edge re-stenosis. This represents less than 18% re-stenosis in a population that would have been expected to exhibit at least 50% re-stenosis at 6 months. A total of 72 patients have been treated either in the pilot study or a subsequent trial. In only one case has a minor spill of radioactivity occurred and in no case has the balloon burst. Radiation doses to staff are approximately 20 microSv per procedure and are therefore not of serious consequence. It is concluded that this procedure is safe, feasible and effective in reducing in-stent re-stenosis.

Angioplasty, Balloon, Coronary↗
PubMed2001

Detection and quantification of intraperitoneal fluid using electrical impedance tomography.

A prototype electrical impedance tomography system was evaluated prior to its use for the detection of intraperitoneal bleeding, with the assistance of patients undergoing continuous ambulatory peritoneal dialysis (CAPD). The system was sensitive enough to detect small amounts of dialysis fluid appearing in subtractive images over short time periods. Uniform sensitivity to blood appearing anywhere within the abdominal cavity was produced using a post-reconstructive filter that corrected for changes in apparent resistivity of anomalies with their radial position. The image parameter used as an indication of fluid quantity, the resistivity index, varied approximately linearly with the quantity of fluid added. A test of the system's response to the introduction of conductive fluid out of the electrode plane (when a blood-equivalent fluid was added to the stomach) found that the sensitivity of the system was about half that observed in the electrode plane. Breathing artifacts were found to upset quantitative monitoring of intraperitoneal bleeding, but only on time scales short compared with the fluid administration rate. Longer term breathing changes, such as those due to variations in the functional residual capacity of the lungs, should ultimately limit the sensitivity over long time periods.

Administration, Oral↗
PubMed2001

Environmental sensitivities: prevalence of major symptoms in a referral center: the Nova Scotia Environmental Sensitivities Research Center Study.

Although the phenomenon of environmental sensitivities (ES) has no clear etiology nor well-accepted pathophysiology, affected individuals experience symptoms that cause varying levels of dysfunction. Through a dedicated, government-funded research and treatment center, a detailed questionnaire covering 217 symptoms in 13 systems was mailed in 1997-1998 to 812 individuals referred to the center by physicians. A total of 385 (47%) questionnaires were returned, and data were analyzed on 351 individuals. Participants tended to be women (80%), middle-aged individuals (37% age 40-49 years), and those in higher educational groups (28% completed university), but there was wide variation in demographic variables. General symptoms such as difficulty concentrating, fatigue, forgetfulness, and irritability dominated the overall prevalence of symptoms since the start of their illness. Those related to irritation such as sneezing, itchy or burning eyes, and hoarseness or loss of voice were more common after exposure to environmental irritants. Ranking of symptoms using severity scores was consistent between men and women. Overall scores were higher in women, in participants who were separated or divorced, and in low-income groups. The type and consistency of symptoms experienced after exposure to triggering substances may not fit a purely psychogenic theory.

Adolescent↗
PubMed2001

The shortened Study Process Questionnaire: an investigation of its structure and longitudinal stability using confirmatory factor analysis.

BACKGROUND: The Study Process Questionnaire (SPQ) is a widely used measure of learning approach and was proposed to have three orientations: surface, deep, and achieving, each with an underlying motive and strategy. AIMS: This study aimed to examine the factor structure and longitudinal stability over five to seven years of a modified shortened 18-item version of the SPQ. SAMPLES: A total of 1349 medical students completed the shortened SPQ at application and in their final year of medical school. Three additional cohorts of students completed the shortened SPQ during their third and fourth year of medical school (sample size: 194, 203, 174). METHOD: Confirmatory factor analysis was used to examine the dimensionality and longitudinal stability of the shortened SPQ. RESULTS: Like the full 42-item version, the shortened SPQ has six subscales and the data are best fit by three second order shared indicator factors (surface, deep and achieving) and a single higher order composite deep-achieving factor. The longitudinal analysis found 26.8%, 26.3%, and 18.7% of the non-attenuated variance of the surface, deep and achieving factor scores in the final year is predicted from the shortened SPQ completed at application to medical school. CONCLUSIONS: The shortened 18-item SPQ has the same six subscales as the full SPQ as well as three second order shared indicator factors (surface, deep, achieving) and one higher order deep-achieving factor similar to that suggested by Biggs (1987). The longitudinal analysis supports this hypothesis and suggests that these learning approaches are partly stable during medical school undergraduate training and partly modifiable under the influence of the educational environment.

Adult↗
PubMed2000

Defining the content for the objective structured clinical examination component of the professional and linguistic assessments board examination: development of a blueprint.

INTRODUCTION: We describe the steps taken to develop an appropriate list of 'clinical problems' used to define the content of the objective structured clinical examination (OSCE) component of the Professional and Linguistic Assessments Board (PLAB) examination. METHOD: A blueprint and list of 255 clinical problems was compiled by reviewing PLAB questions, published curricula of the UK Royal Colleges and other sources such as the General Medical Council's own guidelines. This list was sent to a random sample of 251 successful PLAB candidates who were asked to rate the clinical problems using a scale of 'seen frequently/seldom/never' and to 120 members of the accident and emergency (A&E) specialists' association who were asked to identify 'important' tasks. The list was further validated using activity data obtained for consecutive A&E attendances (934) and admissions (6130) at three hospitals. RESULTS: After two mailings, 131/251 (52%) former PLAB candidates and 89/120 (74%) A&E specialists replied. All of the 255 clinical problems were seen by some former candidates and were felt to be important by some A&E specialists. Of the 255 problems, 40 were neither rated as important nor as seen frequently/seldom by over 50% of respondents. The 255 clinical problems covered a mean 94% consecutive A&E attendances and 97.6% reasons for hospital admission. The correlation between clinical problems that were frequently encountered and those felt to be important was rho=0.38 (P<0.01). CONCLUSION: The clinical problems appear to be appropriate for defining the content of the PLAB OSCE. We suggest that our problem list is useful in that all the problems are seen by some senior house officers, are felt to be important by some A&E specialists and cover greater than or equal to 94% of the conditions for which patients both attend and are admitted from casualty. The correlation between clinical task importance and the frequency that they were seen was only moderate, partly reflecting the relative seriousness of some uncommon medical conditions, which should not be missed on clinical assessment. The content of the OSCE component of the PLAB examination is being reviewed in the light of the findings of this study. The limitations of the study are discussed.

Clinical Competence↗
PubMed2000

A study of pre-registration house officers' clinical skills.

BACKGROUND: Little is known about the ability of pre-registration house officers (PRHOs) to perform basic clinical skills just prior to entering the medical register. OBJECTIVES: To find out whether PRHOs have deficiencies in basic clinical skills and to determine if the PRHOs themselves or their consultants are aware of them. METHOD: All 40 PRHOs at the Chelsea and Westminster and Whittington Hospitals were invited to undertake a 17 station OSCE of basic clinical skills. Each station was marked by one examiner completing an overall global score after completing an itemised checklist. An adequate station performance was the acquisition of a pass/borderline pass grade. Prior to the OSCE, a questionnaire was given to each PRHO asking them to rate their own abilities (on a 5-point scale) in the skills tested. A similar questionnaire was sent to the educational supervisors of each PRHO asking them to rate their house officer's ability in each of the same skills. RESULTS: Twenty-two PRHOs participated. Each PRHO failed to perform adequately a mean of 2.4 OSCE stations (SD 1.8, range 1-8). There were no significant correlations between OSCE performance and either self- or educational supervisor ratings. The supervisor felt unable to give an opinion on PRHO abilities in 18% of the skills assessed. DISCUSSION: This study suggests that PRHOs may have deficiencies in basic clinical skills at the time they enter the medical register. Neither the PRHOs themselves nor their consultants identified these deficiencies. A large regional study with sufficient power is required to explore the generalizability of these concerns in more detail.

Adult↗
PubMed2000

Parenting among Hispanic and Anglo-American mothers with young children.

The authors examined parenting practices and developmental expectations among 38 Hispanic and 38 Anglo-American mothers living in the United States. Mothers of children 3 to 5 years of age completed the Parent Behavior Checklist (R. A. Fox, 1994), a 100-item measure of parents' developmental expectations, discipline, and nurturing practices. In addition, the authors appraised the Hispanic mothers' acculturation and selected them for participation if their scores on an acculturation scale indicated (a) that their lifestyle was predominantly Hispanic and (b) that they had not been assimilated into the dominant culture. The 2 ethnic groups were also divided by socioeconomic status (SES). There were significant main effects for ethnicity and SES on the discipline and nurturing scores but not on the expectations scores. The Hispanic and higher SES mothers reported higher discipline and lower nurturing scores than did the Anglo-American and lower SES mothers. An unexpected finding was the tendency for higher SES Hispanic mothers to report more frequent use of discipline than the other 3 groups.

Adult↗
PubMed2000

The dosimetry for a coronary artery stent coated with radioactive 188Re and 32P.

Radiation dose distributions have been calculated for 188Re and 32P activity on a coronary artery stent. The doses have been calculated both as a function of position along the stent and of depth into the artery wall. Comparisons of the dose from identical activities of 188Re and 32P on the stent show that the major differences arise from the different half-lives of the two activities. Coating the activity onto three surfaces of the stent rather than just the outside surface is found to reduce the dose by approximately 8 to 9%. Similarly, the effect of ignoring the attenuation in the stainless steel of the stent is to increase doses by 11 to 17%. Consideration is also given to the effect of the prolonged treatment times associated with a radioactive stent compared with the more common treatment over several minutes. It is shown that extended treatment may require between two and eight times the single dose to achieve the same effect depending on factors such as the radionuclide used, the dose required and the assumed cell survival curve. On the assumption that an instantaneous dose of 18 Gy at a depth of 1 mm into the artery would be required for successful prevention of neointimal hyperplasia, activities required for a stent coated with 188Re and 32P are tabulated.

Coronary Vessels↗
PubMed2000

Impact on medical students of incorporating GALS screen teaching into the medical school curriculum.

OBJECTIVE: To assess the impact of GALS locomotor screen teaching to all 3rd year medical students, at a British medical school. METHOD: In 1998, during their 3rd year, all students were taught the GALS screen in a one hour small group session. At the end of this year, 242 medical students undertook a 16 station Objective Structured Clinical Examination (OSCE). One station assessed the locomotor screening examination, while six stations assessed the examination of other systems. The students completed a five point likert scale, self rating their confidence in each of the skills assessed at this time. Pre-registration house officers (PRHOs) at two London hospitals were invited to undertake the same OSCE and self rating. RESULTS: The students performed the locomotor screen well (mean station score 80%). Three body systems were examined better and one significantly worse (p<0.05). 22/40 PRHOs undertook the assessment. Compared with the students they examined the locomotor system (mean score 20%, p<0.001), but not other systems, less well. The PRHOs felt less confident (p<0.05) examining the locomotor system (mean rating 3.6/5) than the other systems (mean rating 4.6/5), while no significant difference in confidence ratings was seen for the students. CONCLUSION: Students who are taught the GALS screen as part of the curriculum, perform it well in an end of year OSCE, as confidently as other systems, and to a higher standard than PRHOs. Further study is required to determine whether this benefit persists, overcoming the poor skills and confidence in locomotor examination of existing PRHOs, not previously taught a GALS screen.

Clinical Competence↗
PubMed1999

Intradermal testing for food and chemical sensitivities: a double-blind controlled study.

BACKGROUND: Confirming adverse reactions to foods and chemicals is fundamental in providing a basis for diagnosis and treatment of patients with reported environmental sensitivities. Provocation-neutralization testing is widely used in this respect but has not been thoroughly evaluated, therefore remaining a controversial and unproven technique. OBJECTIVE: This study investigated the validity of intradermal testing for evaluation of reported adverse reactions to a variety of incidents within the patient population at the Nova Scotia Environmental Health Centre. METHODS: A total of 132 people who were referred to the Nova Scotia Environmental Health Centre, a dedicated government-funded research and treatment facility for suspected environmental sensitivities, were tested by the technique of provocation-neutralization by the guidelines set out by the American Academy of Environmental Medicine. A panel of 13 foods, 9 chemicals, and 4 placebos (normal saline solution) was evaluated in a double-blind, randomized study. Symptoms and skin reactions were recorded, and response rates were determined for all substances, including saline solution injections. RESULTS: Seventy percent of the patients reported symptoms to 1 or more of the 4 saline solution injections. In comparison, 15% of patients experienced a skin reaction (wheal) to 1 or more injections of saline solution. Only 5% of individuals experienced a wheal to more than 1 saline solution injection, although 40% of the patients reported symptoms to more than 1 saline injection. Patients who experienced 1 or more reactions (wheal or symptoms) to saline solution were more reactive to injected allergens, on average reacting to 67% of active substances. Patients who experienced no reaction to the saline solution did experience a reaction to 48% of injected substances on average. Reaction by symptoms to foods, chemicals, and normal saline solution showed a random pattern, although wheal reactions showed a distinct pattern. Subsequent observations have indicated that experiencing no reaction to previous saline solution injections does not accurately predict response to saline solution in later testing. Some individuals who did not experience a reaction to saline solution in an initial screening later experienced a reaction to saline solution during further testing. CONCLUSIONS: Provocation of symptoms in usual testing conditions is not a useful tool for discriminating between reactions to saline solution and reactions to specific chemicals or foods. Skin response alone may be a more reliable indicator and will require cross-validation with other tests, such as oral and inhalation challenges and comparison with a control population. Heightened sensitivity and chaotic responses may be a feature of chemical sensitivity. Meanwhile, the results of provocation-neutralization testing, using symptoms alone as an indicator of neutralization, should not be used as a basis for clinical intervention.

Adolescent↗
PubMed1999

Characterizing knowledge deficits in phonological disorders.

To aid the development of finer-grained measures of phonological competence within a representation-based approach to phonology, two aspects of nonsymbolic phonological knowledge (knowledge of the acoustic/perceptual space and of the articulatory/production space) were examined in 6 preschool-age children with phonological disorders and 6 typically developing age peers. To evaluate perceptual knowledge, gating and noise-center tasks were used. Children with phonological disorders recognized significantly fewer words than age peers on both tasks. To evaluate production knowledge, spectral and temporal measures were obtained for CV sequences involving both lingual and labial stop consonants. Group differences on this task (such as larger transition slope values from lingual consonants to vowels for children with phonological disorders) were also observed. These differerences were interpreted as indicating that the children with phonological disorders were less able to maneuver jaw and tongue body separately or that they used "ballistic" (i.e., less controlled) gestures from lingual consonants to vowels than their age peers. These results suggest that phonological knowledge is multifaceted, and that seemingly categorical deficits at one level can be linked to less robust representations at other levels.

Articulation Disorders↗
PubMed1999

The use of GAFchromic film to determine the absolute activity of beta emitters.

A method of using GAFchromic film to determine the absolute activity of beta emitters by immersing the film in a bath of activity is described. This includes calculations of the effect of part of the radioactive solution being displaced by the film that is performing the measurement. Calculations have been performed for 90Y, 32P and 188Re. It is shown that for the film used in this study, this effect will cause a correction of the order of 15-20% for the three radionuclides studied. The results of the GAFchromic film measurement are compared with results obtained from liquid scintillation counting and from a commercial dose calibrator. It is shown that for 32P all methods were in reasonable agreement, but for 188Re, although the GAFchromic film and the liquid scintillation counting methods give similar results, the dose calibrator measurement differed by more than 20%. The GAFchromic film was also used to perform a direct measurement of the radiation dose at a distance of 0.5 mm from the surface of a cylindrical source of 188Re activity. This gave good agreement with the value of the dose predicted from theoretical calculations.

Beta Particles↗
PubMed1999

The effect of contrast medium and balloon shape on dosimetry for arterial irradiation with 188Re.

The radiation dosimetry associated with the use of the beta particle emitter 188Re in an angioplasty balloon is investigated for the case when the balloon has an elliptical rather than circular cross section and when iodinated x-ray contrast medium is included inside the balloon. It is found that the elliptical cross section introduces significant dose corrections when the eccentricity of the ellipse is equal to or greater than 0.7. However, for cases where the artery is nearly circular in cross section, the corrections are likely to be small. As expected, the dose is reduced along the major axis of the ellipse and increased along the minor axis. The corrections are greatest at larger distances from the surface of the balloon. The effect on dose of contrast in the balloon is significant for 33% Omnipaque in saline. Since this is a typical concentration of contrast that is used for imaging the radiation-filled balloon, correction for the effects of contrast medium in the balloon should in general be applied. To enable corrections to be readily applied for other types and concentrations of contrast media, formulas have been derived that allow the dose correction to be calculated for a range of balloon diameters and at various distances from the surface of the balloon. To undertake this calculation, the elemental composition and density of the material in the balloon needs to be known.

Angioplasty, Balloon↗