Identifying studies for systematic reviews - An example from medical imaging

Objectives: To determine if published figures on the proportion of articles included in systematic reviews and identified in electronic databases are applicable to an example from medical imaging. Methods: A systematic review was performed. Additionally, sensitivity and precision of a MEDLINE search were compared with values from three published searches, each customized for a specific field. Results: All articles included in the systematic review were in electronic databases. The MEDLINE search had low precision compared with searches in other fields. Conclusions: in a specific area of medical imaging, electronic databases, including MEDLINE, are reliable sources of articles

Thyroxine treatment in patients with symptoms of hypothyroidism but thyroid function tests within the reference range: randomised double blind placebo controlled crossover trial

OBJECTIVES: To determine whether thyroxine treatment is effective in patients with symptoms of hypothyroidism but with thyroid function tests within the reference range, and to investigate the effect of thyroxine treatment on psychological and physical wellbeing in healthy participants. DESIGN: Randomised double blind placebo controlled crossover trial. SETTING: Outpatient clinic in a general hospital. Participants: 25 patients with symptoms of hypothyroidism who had thyroid function tests within the reference range, and 19 controls. Methods: Participants were given thyroxine 100 microgram or placebo to take once a day for 12 weeks. Washout period was six weeks. They were then given the other to take once a day for 12 weeks. All participants were assessed physiologically and psychologically at baseline and on completion of each phase. MAIN OUTCOME MEASURES: Thyroid function tests, measures of cognitive function and of psychological and physical wellbeing. RESULTS: 22 patients and 19 healthy controls completed the study. At baseline, patients' scores on 9 out of 15 psychological measures were impaired when compared with controls. Patients showed a significantly greater response to placebo than controls in 3 out of 15 psychological measures. Healthy participants had significantly lower scores for vitality when taking thyroxine compared to placebo (mean (SD) 60 (17) v 73 (16), P<0.01). However, patients' scores from psychological tests when taking thyroxine were no different from those when taking placebo except for a poorer performance on one visual reproduction test when taking thyroxine. Serum concentrations of free thyroxine increased and those of thyroid stimulating hormone decreased in patients and controls while they were taking thyroxine, confirming compliance with treatment. Although serum concentrations of free triiodothyronine increased in patients and controls taking thyroxine, the difference between the response to placebo and to thyroxine was significant only in the controls. CONCLUSIONS: Thyroxine was no more effective than placebo in improving cognitive function and psychological wellbeing in patients with symptoms of hypothyroidism but thyroid function tests within the reference range. Thyroxine did not improve cognitive function and psychological wellbeing in healthy participants

How to Undertake a Clinically Relevant Systematic Review in a Rapidly Evolving Field: Magnetic Resonance Angiography

Objectives: The aim was to determine which generations of the evolving technology of magnetic resonance angiography (MRA) are currently of clinical relevance in two clinical applications. Our purpose was to plan a systematic review that would be valuable both to purchasers driven by cost-effectiveness and to practicing clinicians. Methods: Information was gathered from a search of major bibliographic databases, from a short questionnaire sent to 500 U.K. vascular radiologists and vascular surgeons, and from local clinical The authors thank A. Jackson and all those who completed a questionnaire. This work was carried out with the financial support of the Secretary of State for Health under the NHS Health Technology Assessment Programme, project 97/13/04. The views and opinions expressed do not necessarily reflect those of the Secretary of State for Health. In part, this work was undertaken by the Leeds Teaching Hospitals NHS Trust, which received funding from the NHS Executive. The views expressed in this publication are those of the authors and not necessarily those of the NHS Executive.experts. We asked which of the MRA techniques were currently used and, assuming availability, what would be their technique of choice. Results: There were 206 published articles that satisfied preliminary inclusion criteria: 69 discussed 2D time of flight (TOF); 47, 3D TOF; and 38, contrast-enhanced techniques. There were 162 questionnaires returned (60 radiologists, 102 surgeons). Of the total respondents, 77/162 (48%) used MRA in the assessment of carotid artery stenosis; 47/77 (61%) used 2D TOF; 32/77 (42%), 3D TOF; and 26/77 (34%), contrast-enhanced techniques. Thirty-five of 162 (22%) respondents used MRA in the assessment of peripheral vascular disease (PVD); 15/35 (43%) used 2D TOF, 4/35 (11%) used 3D TOF, and 22/35 (63%) used contrast-enhanced techniques. For those wishing to use MRA, contrast-enhanced techniques were the method of choice. Conclusions: The TOF methods that represent earlier generations of the technology remain clinically relevant, and will therefore be included in our systematic review. To ensure complete and relevant coverage in reviews of other evolving technologies, it would be advisable to obtain data for guidance in a similar way

Use of magnetic resonance angiography to select candidates with recently symptomatic carotid stenosis for surgery: systematic review

Objective To determine if sufficient evidence exists to support the use of magnetic resonance angiography as a means of selecting patients with recently symptomatic high grade carotid stenosis for surgery. Design Systematic review of published research on the diagnostic performance of magnetic resonance angiography, 1990-9. Main outcome measures Performance characteristics of diagnostic test. Results 126 potentially relevant articles were identified, but many articles failed to examine die performance of magnetic resonance angiography as a diagnostic test at the surgical decision thresholds used in major clinical trials on endarterectomy. 26 articles were included in a meta-analysis that showed a maximal joint sensitivity and specificity of 99% (95% confidence interval 98% to 100%) for identifying 70-99% stenosis and 90% (81% to 99%) for identifying 50-99% stenosis. Only four articles evaluated contrast enhanced magnetic resonance angiography. Conclusions Magnetic resonance angiography is accurate for selecting patients for carotid endarterectomy at the surgical decision thresholds established in the major endarterectomy trials, but the evidence is not very robust because of the heterogeneity of the studies included. Research is to determine the diagnostic performance of the most recent developments in magnetic resonance angiography, including contrast enhanced techniques, as well as to assess the impact of magnetic resonance angiography on surgical decision making and outcomes

Hypersensitive transport in a phase model with multiplicative stimulus

In a simple system with periodic symmetric potential, the phase model under effect of strong multiplicative noise or periodic square wave, we found a giant response, in the form of directed flux, to an ultrasmall dc signal. The resulting flux demonstrates a bell-shaped dependence on multiplicative noise correlation time and occurs even in the case of large (compared to the signal) additive noise.Comment: 3 EPS figures, submitted to Phys.Lett.

Microscopic Structure of the Calcium Isotopes

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Cognitive development following ART: effect of choice of comparison group, confounding and mediating factors

BACKGROUND: Epidemiological studies have examined the health of children born after assisted reproductive technology (ART), with contradictory results. In this article, we address the question 'Do singletons born after ART have a poorer cognitive developmental outcome at 3 years of age?' We assess the implications of using different comparison groups, and discuss appropriate analytical approaches for the control of confounding and mediating variables. METHODS: Data were drawn from the Millennium Cohort Study. Interviews captured sociodemographic, behavioural and pregnancy information. Developmental assessments conducted at age three included the British Ability Scales II Naming Vocabulary (BAS-NV) instrument. We compared ART infants (born after IVF or ICSI) to four comparison groups: a 'matched' group; a 'subfertile' group (time to conception >12 months); a 'fertile' group (time to conception <12 months); and an 'any spontaneous conceptions' group. Linear regression provided estimates of the difference in mean BAS-NV scores in the ART and comparison groups; both unadjusted estimates and those adjusted for confounding and mediating factors are presented. RESULTS: In the unadjusted analyses, ART children gained significantly better BAS-NV test results than did the comparison group children. When converted to an estimate of developmental age gap, ART children were 2.5, 2.7, 3.6 and 4.5 months ahead of the 'matched', 'subfertile', 'fertile' and 'spontaneous conception' children, respectively. After adjusting for confounding and mediating factors, the differences were reduced, and were not statistically significant. CONCLUSIONS: ART is not associated with poorer cognitive development at 3 years. We have highlighted methodological considerations for researchers planning to study the effect of infertility and ART on childhood outcomes

A model structure for coloured operads in symmetric spectra

We describe a model structure for coloured operads with values in the category of symmetric spectra (with the positive model structure), in which fibrations and weak equivalences are defined at the level of the underlying collections. This allows us to treat R-module spectra (where R is a cofibrant ring spectrum) as algebras over a cofibrant spectrum-valued operad with R as its first term. Using this model structure, we give suficient conditions for homotopical localizations in the category of symmetric spectra to preserve module structures.Comment: 16 page

The effective bandwidth problem revisited

The paper studies a single-server queueing system with autonomous service and $\ell$ priority classes. Arrival and departure processes are governed by marked point processes. There are $\ell$ buffers corresponding to priority classes, and upon arrival a unit of the $k$th priority class occupies a place in the $k$th buffer. Let $N^{(k)}$, $k=1,2,...,\ell$ denote the quota for the total $k$th buffer content. The values $N^{(k)}$ are assumed to be large, and queueing systems both with finite and infinite buffers are studied. In the case of a system with finite buffers, the values $N^{(k)}$ characterize buffer capacities. The paper discusses a circle of problems related to optimization of performance measures associated with overflowing the quota of buffer contents in particular buffers models. Our approach to this problem is new, and the presentation of our results is simple and clear for real applications.Comment: 29 pages, 11pt, Final version, that will be published as is in Stochastic Model

Parents, children and the porous boundaries of the sexual family in law and popular culture

This article focuses on a perceived ideological overlap between popular cultural and judicial treatments of sex and conjugality that contributes to a discursive construction of parenthood and parenting. The author perceives that in both legal and popular cultural texts, there is a sense in which notions of ‘natural’ childhood are discursively constituted as being put at risk by those who reproduce outside of dominant sexual norms, and that signs of normative sexuality (typically in the form of heterosexual coupling) may be treated as a sign of safety. These ideas are rooted in ancient associations between fertility, sexuality and femininity that can also be traced in the historical development of the English language. With the help of commentators such as Martha Fineman, the article situates parents and children within a discourse of family which prioritises conjugality, with consequences for the ways in which the internal and external boundaries of families are delineated