Validation and application of an ensemble Kalman filter in the Selat Pauh of Singapore

The effectiveness of an ensemble Kalman filter (EnKF) is assessed in the Selat Pauh of Singapore using observing system simulation experiment. Perfect model experiments are first considered. The perfect model experiments examine the EnKF in reducing the initial perturbations with no further errors than those in the initial conditions. Current velocity at 15 observational sites from the true ocean is assimilated every hour into the false ocean. While EnKF reduces the initial velocity error during the first few hours, it fails after one tidal cycle (approximately 12 h) due to the rapid convergence of the ensemble members. Successively, errors are introduced in the surface wind forcing. A random perturbation ε [epsilon] is applied independently to each ensemble member to maintain the ensemble spread. The assimilation results showed that the success of EnKF depends critically on the presence of ε [epsilon], yet it is not sensitive to the magnitude of ε [epsilon], at least in the range of weak to moderate perturbations. Although all experiments were made with EnKF only, the results could be applicable in general to all other ensemble-based data assimilation methods.United States. Office of Naval ResearchSingapore. National Research FoundationSingapore-MIT Alliance for Research and Technology CenterSingapore-MIT Alliance. Center for Environmental Sensing and Monitorin

Imbibition in Disordered Media

The physics of liquids in porous media gives rise to many interesting phenomena, including imbibition where a viscous fluid displaces a less viscous one. Here we discuss the theoretical and experimental progress made in recent years in this field. The emphasis is on an interfacial description, akin to the focus of a statistical physics approach. Coarse-grained equations of motion have been recently presented in the literature. These contain terms that take into account the pertinent features of imbibition: non-locality and the quenched noise that arises from the random environment, fluctuations of the fluid flow and capillary forces. The theoretical progress has highlighted the presence of intrinsic length-scales that invalidate scale invariance often assumed to be present in kinetic roughening processes such as that of a two-phase boundary in liquid penetration. Another important fact is that the macroscopic fluid flow, the kinetic roughening properties, and the effective noise in the problem are all coupled. Many possible deviations from simple scaling behaviour exist, and we outline the experimental evidence. Finally, prospects for further work, both theoretical and experimental, are discussed.Comment: Review article, to appear in Advances in Physics, 53 pages LaTe

Change of initial oral antidiabetic therapy in type 2 diabetic patients

Objective To explore the 'real-life' therapy of type 2 diabetes mellitus with oral antidiabetic drugs (OADs). Methods From the PHARMO Record Linkage System comprising linked drug dispensing and clinical laboratory data from approximately 2.5 million individuals in the Netherlands, among others, new users of OADs were identified in the period 1999-2004. New users, aged 30 years and older, without insulin use before cohort entry date and with at least one year follow-up were included. We determined per initial therapy patient characteristics and first therapy change. Results Overall 35,514 patients were included. Metformin and sulfonylureas (SU) were the most frequent initial therapy. Patients on thiazolidinedione (TZD) monotherapy had lower percentages baseline HbA1c ≥ 7% compared to patients on metformin and SU. The proportion of patients still on initial therapy after one year ranged from 46% (TZDs) to around 60% (SU). Among patients starting on monotherapy, add-on (15-20%) and discontinuation (16-25%) of therapy occurred most frequently. In patients starting on combination therapy, a switch occurred in 30% of the patients. Conclusion In more than 40% of the patients a change in initial OAD-therapy is already observed in the first year of therapy. Maintaining patients on initial therapy remains a challenge

Clinical practice guidelines for the foot and ankle in rheumatoid arthritis: a critical appraisal

Background: Clinical practice guidelines are recommendations systematically developed to assist clinical decision-making and inform healthcare. In current rheumatoid arthritis (RA) guidelines, management of the foot and ankle is under-represented and the quality of recommendation is uncertain. This study aimed to identify and critically appraise clinical practice guidelines for foot and ankle management in RA. Methods: Guidelines were identified electronically and through hand searching. Search terms 'rheumatoid arthritis', 'clinical practice guidelines' and related synonyms were used. Critical appraisal and quality rating were conducted using the Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument. Results: Twenty-four guidelines were included. Five guidelines were high quality and recommended for use. Five high quality and seven low quality guidelines were recommended for use with modifications. Seven guidelines were low quality and not recommended for use. Five early and twelve established RA guidelines were recommended for use. Only two guidelines were foot and ankle specific. Five recommendation domains were identified in both early and established RA guidelines. These were multidisciplinary team care, foot healthcare access, foot health assessment/review, orthoses/insoles/splints, and therapeutic footwear. Established RA guidelines also had an 'other foot care treatments' domain. Conclusions: Foot and ankle management for RA features in many clinical practice guidelines recommended for use. Unfortunately, supporting evidence in the guidelines is low quality. Agreement levels are predominantly 'expert opinion' or 'good clinical practice'. More research investigating foot and ankle management for RA is needed prior to inclusion in clinical practice guidelines

Collaborating with front-line healthcare professionals: the clinical and cost effectiveness of a theory based approach to the implementation of a national guideline

Background Clinical guidelines are an integral part of healthcare. Whilst much progress has been made in ensuring that guidelines are well developed and disseminated, the gap between routine clinical practice and current guidelines often remains wide. A key reason for this gap is that implementation of guidelines typically requires a change in the behaviour of healthcare professionals – but the behaviour change component is often overlooked. We adopted the Theoretical Domains Framework Implementation (TDFI) approach for supporting behaviour change required for the uptake of a national patient safety guideline to reduce the risk of feeding through misplaced nasogastric tubes. Methods The TDFI approach was used in a pre-post study in three NHS hospitals with a fourth acting as a control (with usual care and no TDFI). The target behavior identified for change was to increase the use of pH testing as the first line method for checking the position of a nasogastric tube. Repeat audits were undertaken in each hospital following intervention implementation. We used Zou’s modified Poisson regression approach with robust standard errors to estimate risk ratios for the use of pH testing. The projected return on investment (ROI) was also calculated. Results Following intervention implementation, the use of pH first line increased significantly across intervention hospitals [risk ratio (95% CI) ranged from 3.1 (1.14 to8.43) p < .05, to 8.14 (3.06 to21.67) p < .001] compared to the control hospital, which remained unchanged [risk ratio (CI) = .77 (.47-1.26) p = .296]. The estimated savings and costs in the first year were £2.56 million and £1.41 respectively, giving an ROI of 82%, and this was projected to increase to 270% over five years. Conclusion The TDFI approach improved the uptake of a patient safety guideline across three hospitals. The TDFI approach is clinically and cost effective in comparison to the usual practice

The systematic guideline review: method, rationale, and test on chronic heart failure

Background: Evidence-based guidelines have the potential to improve healthcare. However, their de-novo-development requires substantial resources-especially for complex conditions, and adaptation may be biased by contextually influenced recommendations in source guidelines. In this paper we describe a new approach to guideline development-the systematic guideline review method (SGR), and its application in the development of an evidence-based guideline for family physicians on chronic heart failure (CHF). Methods: A systematic search for guidelines was carried out. Evidence-based guidelines on CHF management in adults in ambulatory care published in English or German between the years 2000 and 2004 were included. Guidelines on acute or right heart failure were excluded. Eligibility was assessed by two reviewers, methodological quality of selected guidelines was appraised using the AGREE instrument, and a framework of relevant clinical questions for diagnostics and treatment was derived. Data were extracted into evidence tables, systematically compared by means of a consistency analysis and synthesized in a preliminary draft. Most relevant primary sources were re-assessed to verify the cited evidence. Evidence and recommendations were summarized in a draft guideline. Results: Of 16 included guidelines five were of good quality. A total of 35 recommendations were systematically compared: 25/35 were consistent, 9/35 inconsistent, and 1/35 un-rateable (derived from a single guideline). Of the 25 consistencies, 14 were based on consensus, seven on evidence and four differed in grading. Major inconsistencies were found in 3/9 of the inconsistent recommendations. We re-evaluated the evidence for 17 recommendations (evidence-based, differing evidence levels and minor inconsistencies) - the majority was congruent. Incongruity was found where the stated evidence could not be verified in the cited primary sources, or where the evaluation in the source guidelines focused on treatment benefits and underestimated the risks. The draft guideline was completed in 8.5 man-months. The main limitation to this study was the lack of a second reviewer. Conclusion: The systematic guideline review including framework development, consistency analysis and validation is an effective, valid, and resource saving-approach to the development of evidence-based guidelines

Reliability and validity of the AGREE instrument used by physical therapists in assessment of clinical practice guidelines

BACKGROUND: The AGREE instrument has been validated for evaluating Clinical Practice Guidelines (CPG) pertaining to medical care. This study evaluated the reliability and validity of physical therapists using the AGREE to assess quality of CPGs relevant to physical therapy practice. METHODS: A total of 69 physical therapists participated and were classified as generalists, specialist or researchers. Pairs of appraisers within each category evaluated independently, a set of 6 CPG selected at random from a pool of 55 CPGs. RESULTS: Reliability between pairs of appraisers indicated low to high reliability depending on the domain and number of appraisers (0.17–0.81 for single appraiser; 0.30–0.96 when score averaged across a pair of appraisers). The highest reliability was achieved for Rigour of Development, which exceeded ICC> 0.79, if scores from pairs of appraisers were pooled. Adding more than 3 appraisers did not consistently improve reliability. Appraiser type did not determine reliability scores. End-users, including study participants and a separate sample of 102 physical therapy students, found the AGREE useful to guide critical appraisal. The construct validity of the AGREE was supported in that expected differences on Rigour of Development domains were observed between expert panels versus those with no/uncertain expertise (differences of 10–21% p = 0.09–0.001). Factor analysis with varimax rotation, produced a 4-factor solution that was similar, although not in exact agreement with the AGREE Domains. Validity was also supported by the correlation observed (Kendall-tao = 0.69) between Overall Assessment and the Rigour of Development domain. CONCLUSION: These findings suggest that the AGREE instrument is reliable and valid when used by physiotherapists to assess the quality of CPG pertaining to physical therapy health services

STORIES Statement: publication standards for healthcare education evidence synthesis

Fully copy of the STORIES statement - a checklist of reporting guidance for health education evidence synthesis Structured approach for Reporting In health education of Evidence Synthesis Background Evidence synthesis techniques in healthcare education have been enhanced through the activities of experts in the field and the Best Evidence Medical Education (BEME) collaborative. Despite this, significant heterogeneity in techniques and reporting of healthcare education systematic review still exist and limit the usefulness of such reports. The aim of this project was to produce the STORIES (STructured apprOach to the Reporting In healthcare education of Evidence Synthesis) statement to offer a guide for reporting evidence synthesis in health education for use by authors and journal editors. Methods A review of existing published evidence synthesis consensus statements was undertaken. A modified Delphi process was used. In stage one, expert participants were asked to state whether common existing items identified were relevant, to suggest relevant texts and specify any items they feel should be included. The results were analysed and a second stage commenced where all synthesised items were presented and participants asked to state whether they should be included or amend as needed. After further analysis, the full statement was sent for final review and comment. Results Nineteen experts participated in the panel from 35 invitations. Thirteen text sources were proposed, six existing items amended and twelve new items synthesised. After stage two, 25 amended consensus items were proposed for inclusion. The final statement contains several items unique to this context, including description of relevant conceptual frameworks or theoretical constructs, description of qualitative methodologies with rationale for their choice and presenting the implications for educators in practice of the results obtained. Conclusions An international expert panel has agreed upon a consensus statement of 25 items for the reporting of evidence synthesis within healthcare education. This unique set of items is focused on context, rather than a specific methodology. This statement can be used for those writing for publication and reviewing such manuscripts to ensure reporting supports and best informs the wider healthcare education community

Inflammation in the male genital tract: implications for HIV acquisition and transmission

Elevated plasma levels of pro-inflammatory mediators such as TNFα, IL-1β, IL-6 and IL-8, MIP-1α, MIP-1β and RANTES have been demonstrated in HIV-infected individuals and HIV induces higher levels of pro-inflammatory cytokines in the female genital tract. We characterized levels of inflammation in semen, to gain an understanding of factors influencing transmission and acquisition in the male genital tract. Our hypothesis was that infected men would exhibit higher levels of inflammation in semen than uninfected men