Dawn Coleby

Analysis of techniques to compare complex data sets.

This paper analyses a number of techniques that can be used to compare complex data sets, such as those arising from electromagnetic simulation and experimentation. The techniques assessed are: correlation, several reliability factors and feature selective validation. The study examines the performance of each technique for data comparison. The paper provides a comprehensive summary of the techniques and compares their performance and comments on their use in the validation of numerical modelling codes and model designs.

The integrated error against log frequency (IELF) method for CEM validation

Data with a high feature density is common within EMC measurements and modeling, particularly in the complex and substantially overmoded environments found in aerospace EMC environments. Comparison of experimental and modeled data based on visual assessment of the graphical representation of the data is common and requires both extensive experience and detailed system knowledge in order to be able to interpret the comparisons with confidence. However, in circumstances where a quantification of this comparison is called for, such as when sharing results across partner organizations, obtaining a single representative figure of merit is challenging. The integrated error against log frequency (IELF) method was developed to provide this quantification. It is based on the view that the most significant aspect of the data to be compared is a function of the difference between the two traces being compared, particularly when the individual features are difficult to discriminate. This paper presents the IELF method and demonstrates its potential.

Progress in quantifying validation data

There are a number of reasons why a numerical value is a desirable outcome for the validation of numerical models: these include the desire to report objectively and succinctly on the comparison with a benchmark result, and the need to rank order implementations of a canonical problem. The key challenge is to develop techniques which provide a numerical output that do not challenge excessively the interpretations of experienced engineers and which presents both sufficient discrimination between comparisons and consistency across the various sub-disciplines of EMC. While this paper concentrates on the subject of numerical code generation, the rationale and associated concepts are just as relevant to other aspects of EMC such as quantifying experimental repeatability. The purpose of this paper is to present some of the work done to date on generating a numerical value representing the overall quality of comparison for two sets of data. This paper reviews and contrasts various techniques currently available to produce this numerical overview. The techniques include correlograms, feature selective validation (FSV), integrated error against log frequency (IELF) and reliability factors. The paper concludes that the most taxing aspect of the work required to develop such techniques is benchmarking against human interpretation, a rating scale is discussed which can assist in obtaining this information.

Delay between symptom onset and clinic attendance following TIA and minor stroke: the BEATS study

BACKGROUND rapid specialist assessment of patients with transient ischaemic attack (TIA) reduces the risk of recurrent stroke. National guidelines advise that high-risk patients are assessed within 24 h and low-risk patients within 7 days. AIM to quantify delay and map pathways taken by patients from symptom onset to specialist assessment. DESIGN retrospective cohort study. SETTING rapid access TIA clinic. METHODS structured interviews with 278 patients newly diagnosed with TIA (222) or minor stroke (56), and examination of medical records. RESULTS of the 133 high-risk TIA patients, 11 (8%) attended the clinic within 24 h of symptom onset; of the 89 low-risk TIA patients, 47 (53%) attended within 7 days. Median delay between symptom onset and seeking help from a healthcare professional (HCP) was 4.0 h (IQR 0.5, 41.3). Delay was less if symptoms were correctly interpreted but not reduced by a publicity campaign (FAST) to encourage an urgent response. Most patients (156, 56%) first contacted a general practitioner (GP) and 46 (17%) called an ambulance or attended the emergency department. Over a third (36%) had a second consultation with an HCP before attending the clinic, and this was more likely in those presenting to paramedics, out of hours GP services or optometry. Time to clinic attendance was less if an emergency pathway was used and greater if patients were seen by a second HCP. CONCLUSIONS factors contributing to delay include incorrect interpretation of symptoms and failure to invoke emergency services. Delays after presentation could be addressed by direct referral by out of hours services, paramedics and optometrists.

A visual interpretation rating scale for validation of numerical models

Purpose – The comparison of large volumes of complex data resulting from numerical modelling in computational electromagnetics is a demanding task, especially when validating the performance of numerical models against experimental results and testing experimental repeatability. “By‐eye” comparisons can lead to inconsistencies and inherent subjectivity. This paper establishes a “visual” benchmark by which comparisons can be made and therefore used to assist in the development of an algorithmic approach to data comparison.Design/methodology/approach – This new method presented here is based on the Cooper‐Harper Rating Scale, which is a test pilots evaluation‐rating instrument. This has been modified through qualitative research. The assertion that the rating scale will leave the group mean response unaltered but will reduce the variance has been statistically tested.Findings – The proposed rating scale provides a calibration technique by which to benchmark comparisons. The scale also reduces subjectivity ...

Mapping midwifery and obstetric units in England

OBJECTIVE to describe the configuration of midwifery units, both alongside&free-standing, and obstetric units in England. DESIGN national survey amongst Heads of Midwifery in English Maternity Services SETTING: National Health Service (NHS) in England PARTICIPANTS: English Maternity Services Measurements descriptive statistics of Alongside Midwifery Units and Free-standing Midwifery Units and Obstetric Units and their annual births/year in English Maternity Services FINDINGS: alongside midwifery units have nearly doubled since 2010 (n = 53-97); free-standing midwifery units have increased slightly (n = 58-61). There has been a significant reduction in maternity services without either an alongside or free-standing midwifery unit (75-32). The percentage of all births in midwifery units has trebled, now representing 14% of all births in England. This masks significant differences in percentage of all births in midwifery units between different maternity services with a spread of 4% to 31%. KEY CONCLUSIONS In some areas of England, women have no access to a local midwifery unit, despite the National Institute for Health&Clinical Excellence (NICE) recommending them as an important place of birth option for low risk women. The numbers of midwifery units have increased significantly in England since 2010 but this growth is almost exclusively in alongside midwifery units. The percentage of women giving birth in midwifery units varies significantly between maternity services suggesting that many midwifery units are underutilised. IMPLICATIONS FOR PRACTICE Both the availability and utilisation of midwifery units in England could be improved.

Service factors causing delay in specialist assessment for TIA and minor stroke: a qualitative study of GP and patient perspectives.

Objective To understand how service factors contribute to delays to specialist assessment following transient ischaemic attack (TIA) or minor stroke. Design Qualitative study using semistructured interviews, analysis by constant comparison. Setting Leicester, UK. Participants Patients diagnosed with TIA or minor stroke, at hospital admission or in a rapid-access TIA clinic (n=42), general practitioners (GPs) of participating patients if they had been involved in the patients’ care (n=18). Data Accounts from patients and GPs of factors contributing to delay following action to seek help from a healthcare professional (HCP). Results The following categories of delay were identified. First, delay in assessment in general practice following contact with the service; this related to availability of same day appointments, and the role of the receptionist in identifying urgent cases. Second, delays in diagnosis by the HCP first consulted, including GPs, optometrists, out-of-hours services, walk-in centres and the emergency department. Third, delays in referral after a suspected diagnosis; these included variable use of the ABCD2 (Age, Blood pressure, Clinical features, Duration, Diabetes) risk stratification score and referral templates in general practice, and referral back to the patients’ GP in cases where he/she was not the first HCP consulted. Conclusions Primary and emergency care providers need to review how they can best handle patients presenting with symptoms that could be due to stroke or TIA. In general practice, this may include receptionist training and/or triage by a nurse or doctor. Mechanisms need to be established to enable direct referral to the TIA clinic when patients whose symptoms have resolved present to other agencies. Further work is needed to improve diagnostic accuracy by non-specialists.

Long term follow-up of a randomised controlled trial of services for urinary symptoms

BackgroundGiven the extent and priority of urinary symptoms there is little evidence available to inform service provision in relation to the long term effects of interventions. This study aims to determine the long term (6 year) clinical effectiveness and costs of a new continence nurse led service compared to standard care for urinary symptoms.MethodsA long term follow-up study of a 2-arm, non-blinded randomised controlled trial that recruited from a community based population between 1998-2000 in Leicestershire and Rutland UK was undertaken. 3746 men and women aged 40 years and over were followed up from the original trial. The continence nurse practitioner (CNP) intervention comprised a continence service provided by specially trained nurses delivering evidence-based interventions using pre-determined care pathways. The standard care (SC) arm comprised access to existing primary care including General Practitioner and continence advisory services in the area. Primary outcome: Improvement in one or more symptom. Secondary outcomes included: a) Leicester Impact scale; b) patient perception of problem; c) number of symptoms alleviated and cost-effectiveness; all were recorded at long term follow-up (average 6 years) post-randomisation.ResultsOverall at long-term follow-up (average 6 years) significantly more individuals in the CNP group (72%) had improved (i.e had fewer symptoms) compared to those in the SC group (67%) (difference of 5% 95% (CI = 0.6 to 9;p = 0.02)).ConclusionThe differences in outcome between the two randomised groups shown immediately post treatment had decreased by half in terms of symptom improvement at long term follow-up. Although the difference was statistically significant, the clinical significance may not be, although the direction of the difference favoured the new CNP service.

Measuring similarity for validation of computational electromagnetic modelling

Computational electromagnetics has been widely used since the ascendancy of computing. Validation of the resulting models has been a constant theme for developers, vendors and users, each wanting to be as confident as possible that the technique, code or model they are working with provides acceptable results in the situation in which it is being applied. However, no standardized procedure has been accepted to support this activity. A current IEEE activity aims to address this need, particularly with reference to applications in electromagnetic compatibility. One substantial question is how can confidence be quantified, allowing models to be compared with measurements to determine accuracy, or to compare models against other models to determine the level of difference. This paper addresses the issue of quantifying confidence setting this topic firmly in the progress of the standard activity to date.

Can site performance be predicted? Results of an evaluation of the performance of a site selection questionnaire in five multicentre trials

Background Site Selection Questionnaires (SSQs) have evolved to become “best” practice for commercial and non-commercial clinical trials. There has been limited evaluation of such questionnaires, however, and there is no generally accepted tool or methodology for selecting suitable sites for inclusion in a trial. Nottingham Clinical Trials Unit introduced a site selection questionnaire in 2010, this paper will present evaluation of the questionnaire’s performance in five trials.