On Reliability Assessment When a Software-based System Is Replaced by a Thought-to-be-Better One

The failure history of pre-existing systems can inform a reliability assessment of a new system. Such assessments – consisting of arguments based on evidence from older systems – are attractive and have been used for quite some time for, typically, mechanical/hardware-only systems. But their application to software-based systems brings some challenges. In this paper, we present a conservative, Bayesian approach to software reliability assessment – one that combines reliability evidence from an old system with an assessor’s confidence in a newer system being an improved replacement for the old one. We demonstrate, via different scenarios, what a thought-to-be-better replacement formally means in practice, and what it allows one to believe about actual reliability improvement. The results can be used directly in a reliability assessment, or to caution system stakeholders and industry regulators against using other models that give optimistic assessments. For instance, even if one is certain that some new software must be more reliable than an old product, using the reliability distribution for the old software as a prior distribution when assessing the new system gives optimistic, not conservative, predictions for the posterior reliability of the new system after seeing operational testing evidence

Estimating worst case failure dependency with partial knowledge of the difficulty function

For systems using software diversity, well-established theories show that the expected probability of failure on demand (pfd) for two diverse program versions failing together will generally differ from what it would be if they failed independently. This is explained in terms of a “difficulty function” that varies between demands on the system. This theory gives insight, but no specific prediction unless we have some means to quantify the difficulty function. This paper presents a theory leading to a worst case measure of “average failure dependency” between diverse software, given only partial knowledge of the difficulty function. It also discusses the possibility of estimating the model parameters, with one approach based on an empirical analysis of previous systems implemented as logic networks, to support pre-development estimates of expected gain from diversity. The approach is illustrated using a realistic safety system example

Blood pressure control and left ventricular hypertrophy in hypertensive Nigerians

Background : Hypertension is a disease characterized by end-organ complications, leading to high morbidity and mortality in many cases. People with untreated or uncontrolled hypertension often run the risk of developing complications directly associated with the disease. Left ventricular hypertrophy (LVH) has been shown to be a significant risk factor for adverse outcomes both in patients with hypertension and in the general population. We investigated the prevalence and pattern of LVH in a treated hypertensive population at the University College Hospital, Ibadan, Nigeria, using non-hypertensive subjects as control. Design and Setting : A prospective observational study performed at the University College Hospital, Ibadan, Nigeria. Methods : Patients had 6 visits, when at least one blood pressure measurement was recorded for each hypertensive subject and average calculated for systolic blood pressure (SBP) and diastolic blood pressure (DBP) separately. The values obtained were used for stratification of the subjects into controlled and uncontrolled hypertension. Subjects also had echocardiograms to determine their left ventricular mass. Results : LVH was found in 14 (18.2%) of the normotensive group, 40 (20.8%) of the uncontrolled hypertensive group and 14 (24.1%) of the controlled hypertensive group when left ventricular mass (LVM) was indexed to body surface area (BSA). When LVM was indexed to height, left ventricular hypertrophy was found in none of the subjects of the normotensive group, while it was found present in 43 (22.4%) and 14 (24.1%) subjects of the uncontrolled and controlled hypertensive groups, respectively. Significant difference in the prevalence of LVH was detected only when LVM was indexed to height alone. Conclusion : Clinic blood pressure is an ineffective way of assessing BP control. Thus in apparently controlled hypertensive subjects, based on office blood pressure, cardiac structural changes do remain despite antihypertensive therapy. This population is still at risk of cardiovascular events.arri\ue8re-plan: l\u2019hypertension est une maladie caract\ue9ris\ue9e par l\u2019orgue de fi n complications menant \ue0 \ue9lev\ue9 de morbidit\ue9 et mortalit\ue9 dans de nombreux cas. Personnes avec l\u2019hypertension non trait\ue9e ou non contr\uf4l\ue9e souvent risquent de d\ue9velopper complications directement associ\ue9es \ue0 la maladie. Laiss\ue9 ventriculaire hypertrophie (LVH) a \ue9t\ue9 d\ue9montr\ue9 un facteur de risque signifi catif pour les effets n\ue9gatifs r\ue9sultats tant chez les patients atteints de l\u2019hypertension et de la population g\ue9n\ue9rale. Nous avons a enqu\ueat\ue9 sur la pr\ue9valence et le mod\ue8le de LVH dans un trait\ue9 hypertendues population au University College Hospital, \ue0 l\u2019aide Ibadan, Nigeria non-hypertendues des sujets comme contr\uf4le. conception et la confi guration: A \ue9ventuel \ue9tude d\u2019observation effectu\ue9e \ue0 la University College Hospital, Ibadan, Nigeria. m\ue9thodes: Patients avaient six visites o\uf9 au moins un sang mesure de pression a \ue9t\ue9 enregistr\ue9e pour chaque sujet hypertendues et moyenne calcul\ue9s s\ue9par\ue9ment pour SBP et DBP. Les valeurs obtenues ont \ue9t\ue9 utilis\ue9es pour stratifi cation des sujets dans l\u2019hypertension contr\uf4l\ue9e et incontr\uf4l\ue9e. Sujets ont \ue9galement echocardiograms pour d\ue9terminer leur masse ventriculaire gauche. r\ue9sultats: LVH a \ue9t\ue9 trouv\ue9 en 14(18.2%) de la groupe normotensive, 40(20.8%) de groupe de hypertendues non contr\uf4l\ue9es et 14(24.1%) de hypertendues contr\uf4l\ue9e groupe lorsque quitt\ue9 masse ventriculaire (LVM) a \ue9t\ue9 index\ue9e \ue0 corps surface (BSA). Lorsque LVM a \ue9t\ue9 index\ue9 \ue0 hauteur, laiss\ue9 ventriculaire hypertrophie a \ue9t\ue9 trouv\ue9 dans aucun du groupe normotensive, bien qu\u2019il a \ue9t\ue9 constat\ue9 pr\ue9sents dans les 43(22.4%) et 14(24.1%) de hypertendues non ma\ueetris\ue9e et contr\uf4l\ue9e groupes respectivement. \uc9tait de diff\ue9rence signifi cative dans la pr\ue9valence de la LVH d\ue9tect\ue9s uniquement lorsque LVM a \ue9t\ue9 index\ue9 \ue0 hauteur alone. conclusion: clinique art\ue9rielle est un moyen ineffi cace de mesurer le contr\uf4le de BP. Ainsi en sujet hypertendues apparemment contr\uf4l\ue9e bas\ue9e sur la pression art\ue9rielle de bureau, des changements structurels cardiaques restent malgr\ue9 th\ue9rapie antihypertensive. Cette population est toujours \ue0 risque de maladies cardiovasculaires \ue9v\ue9nements

Stakeholder perspectives and requirements to guide the development of digital technology for palliative cancer services: a multi-country, cross-sectional, qualitative study in Nigeria, Uganda and Zimbabwe

Introduction: Coverage of palliative care in low and middle-income countries is very limited, and global projections suggest large increases in need. Novel approaches are needed to achieve the palliative care goals of Universal Health Coverage. This study aimed to identify stakeholders’ data and information needs and the role of digital technologies to improve access to and delivery of palliative care for people with advanced cancer in Nigeria, Uganda and Zimbabwe. Methods: We conducted a multi-country cross-sectional qualitative study in sub-Saharan Africa. In-depth qualitative stakeholder interviews were conducted with N = 195 participants across Nigeria, Uganda and Zimbabwe (advanced cancer patients n = 62, informal caregivers n = 48, health care professionals n = 59, policymakers n = 26). Verbatim transcripts were subjected to deductive and inductive framework analysis to identify stakeholders needs and their preferences for digital technology in supporting the capture, transfer and use of patient-level data to improve delivery of palliative care. Results: Our coding framework identified four main themes: i) acceptability of digital technology; ii) current context of technology use; iii) current vision for digital technology to support health and palliative care, and; iv) digital technologies for the generation, reporting and receipt of data. Digital heath is an acceptable approach, stakeholders support the use of secure data systems, and patients welcome improved communication with providers. There are varying preferences for how and when digital technologies should be utilised as part of palliative cancer care provision, including for increasing timely patient access to trained palliative care providers and the triaging of contact from patients. Conclusion: We identified design and practical challenges to optimise potential for success in developing digital health approaches to improve access to and enhance the delivery of palliative cancer care in Nigeria, Uganda and Zimbabwe. Synthesis of findings identified 15 requirements to guide the development of digital health approaches that can support the attainment of global health palliative care policy goals

A high performance liquid chromatographic assay of Mefloquine in saliva after a single oral dose in healthy adult Africans

<p>Abstract</p> <p>Background</p> <p>Mefloquine-artesunate is a formulation of artemisinin based combination therapy (ACT) recommended by the World Health Organization and historically the first ACT used clinically. The use of ACT demands constant monitoring of therapeutic efficacies and drug levels, in order to ensure that optimum drug exposure is achieved and detect reduced susceptibility to these drugs. Quantification of anti-malarial drugs in biological fluids other than blood would provide a more readily applicable method of therapeutic drug monitoring in developing endemic countries. Efforts in this study were devoted to the development of a simple, field applicable, non-invasive method for assay of mefloquine in saliva.</p> <p>Methods</p> <p>A high performance liquid chromatographic method with UV detection at 220 nm for assaying mefloquine in saliva was developed and validated by comparing mefloquine concentrations in saliva and plasma samples from four healthy volunteers who received single oral dose of mefloquine. Verapamil was used as internal standard. Chromatographic separation was achieved using a Hypersil ODS column.</p> <p>Results</p> <p>Extraction recoveries of mefloquine in plasma or saliva were 76-86% or 83-93% respectively. Limit of quantification of mefloquine was 20 ng/ml. Agreement between salivary and plasma mefloquine concentrations was satisfactory (r = 0.88, <it>p </it>< 0.001). Saliva:plasma concentrations ratio was 0.42.</p> <p>Conclusion</p> <p>Disposition of mefloquine in saliva paralleled that in plasma, making salivary quantification of mefloquine potentially useful in therapeutic drug monitoring.</p

Understanding data and information needs for palliative cancer care to inform digital health intervention development in Nigeria, Uganda and Zimbabwe: protocol for a multicountry qualitative study

Introduction: Palliative care is a clinically and cost‐effective component of cancer services in sub-Saharan Africa (SSA). Despite the significant need for palliative cancer care in SSA, coverage remains inadequate. The exploration of digital health approaches could support increases in the quality and reach of palliative cancer care services in SSA. However, there is currently a lack of any theoretical underpinning or data to understand stakeholder drivers for digital health components in this context. This project addresses this gap through engaging with key stakeholders to determine data and information needs that could be supported through digital health interventions. Methods and analysis: This is a multicountry, cross-sectional, qualitative study conducted in Nigeria, Uganda and Zimbabwe. In-depth interviews will be conducted in patients with advanced cancer (n=20), caregivers (n=15), health professionals (n=20) and policy-makers (n=10) in each of the three participating countries. Data from a total of 195 interviews will transcribed verbatim and translated into English before being imported into NVivo software for deductive framework analysis. The analysis will seek to understand the acceptability and define mechanisms of patient-level data capture and usage via digital technologies. Ethics and dissemination: Ethics approvals have been obtained from the Institutional Review Boards of University of Leeds (Ref: MREC 18–032), Research Council of Zimbabwe (Ref: 03507), Medical Research Council of Zimbabwe (Ref: MRCZ/A/2421), Uganda Cancer Institute (Ref: 19–2018), Uganda National Council of Science and Technology (Ref: HS325ES) and College of Medicine University of Lagos (Ref: HREC/15/04/2015). The project seeks to determine optimal mechanisms for the design and development of subsequent digital health interventions to support development, access to, and delivery of palliative cancer care in SSA. Dissemination of these findings will occur through newsletters and press releases, conference presentations, peer-reviewed journals and social media. Trial registration number: ISRCTN1572771

Practical examination of bystanders performing Basic Life Support in Germany: a prospective manikin study

<p>Abstract</p> <p>Background</p> <p>In an out-of-hospital emergency situation bystander intervention is essential for a sufficient functioning of the chain of rescue. The basic measures of cardiopulmonary resuscitation (Basic Life Support – BLS) by lay people are therefore definitely part of an effective emergency service of a patient needing resuscitation. Relevant knowledge is provided to the public by various course conceptions. The learning success concerning a one day first aid course ("LSM" course in Germany) has not been much investigated in the past. We investigated to what extent lay people could perform BLS correctly in a standardised manikin scenario. An aim of this study was to show how course repetitions affected success in performing BLS.</p> <p>Methods</p> <p>The "LSM course" was carried out in a standardised manner. We tested prospectively 100 participants in two groups (<b>Group 1: </b>Participants with previous attendance of a BLS course; <b>Group 2: </b>Participants with no previous attendance of a BLS course) in their practical abilities in BLS after the course. Success parameter was the correct performance of BLS in accordance with the current ERC guidelines.</p> <p>Results</p> <p>Twenty-two (22%) of the 100 investigated participants obtained satisfactory results in the practical performance of BLS. Participants with repeated participation in BLS obtained significantly better results (<b>Group 1: </b>32.7% vs. <b>Group 2: </b>10.4%; p < 0.01) than course participants with no relevant previous knowledge.</p> <p>Conclusion</p> <p>Only 22% of the investigated participants at the end of a "LSM course" were able to perform BLS satisfactorily according to the ERC guidelines. Participants who had previously attended comparable courses obtained significantly better results in the practical test. Through regular repetitions it seems to be possible to achieve, at least on the manikin, an improvement of the results in bystander resuscitation and, consequently, a better patient outcome. To validate this hypothesis further investigations are recommended by specialised societies.</p

Why caretakers bypass Primary Health Care facilities for child care - a case from rural Tanzania

<p>Abstract</p> <p>Background</p> <p>Research on health care utilization in low income countries suggests that patients frequently bypass PHC facilities in favour of higher-level hospitals - despite substantial additional time and financial costs. There are limited number of studies focusing on user's experiences at such facilities and reasons for bypassing them. This study aimed to identify factors associated with bypassing PHC facilities among caretakers seeking care for their underfive children and to explore experiences at such facilities among those who utilize them.</p> <p>Methods</p> <p>The study employed a mixed-method approach consisting of an interviewer administered questionnaires and in-depth interviews among selected care-takers seeking care for their underfive children at Korogwe and Muheza district hospitals in north-eastern Tanzania.</p> <p>Results</p> <p>The questionnaire survey included 560 caretakers. Of these 30 in-depth interviews were conducted. Fifty nine percent (206/348) of caretakers had not utilized their nearer PHC facilities during the index child's sickness episode. The reasons given for bypassing PHC facilities were lack of possibilities for diagnostic facilities (42.2%), lack of drugs (15.5%), closed health facility (10.2%), poor services (9.7%) and lack of skilled health workers (3.4%). In a regression model, the frequency of bypassing a PHC facility for child care increased significantly with decreasing travel time to the district hospital, shorter duration of symptoms and low disease severity.</p> <p>Findings from the in-depth interviews revealed how the lack of quality services at PHC facilities caused delays in accessing appropriate care and how the experiences of inadequate care caused users to lose trust in them.</p> <p>Conclusion</p> <p>The observation that people are willing to travel long distances to get better quality services calls for health policies that prioritize quality of care before quantity. In a situation with limited resources, utilizing available resources to improve quality of care at available facilities could be more appropriate for improving access to health care than increasing the number of facilities. This would also improve equity in health care access since the poor who can not afford travelling costs will then get access to quality services at their nearer PHC facilities.</p