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Introduction: Acute uncomplicated urinary tract infection (UTI) is a common condition with potentially serious sequelae that is mostly diagnosed and managed in primary care settings. Around half of all women have a UTI in their lifetime, and a quarter experience an infection caused by organisms resistant to more than one antibiotic. Reducing inappropriate prescribing of antibiotics is a core tenet of antimicrobial stewardship. However, current diagnostics for UTI are unfit for purpose in acute (highest prescribing) settings, being too slow to inform the required immediate decision-making and often confounded by sample contamination.Rapid point-of-care diagnostic tests (POCTs) that facilitate timely decision-making are potential solutions to this problem. Several such tests have reached advanced stages of technology readiness, but their diagnostic performance has not been evaluated in primary care with clinical users. To progress novel tests towards implementation, a diagnostic field study is required, to allow for parallel and sequential evaluation of multiple tests in a primary care population., Methods and Analysis: We will recruit participants assigned female at birth from primary care clinics in England who contact their clinic with symptoms of acute uncomplicated UTI. Eligible participants will complete a short questionnaire to capture symptoms and symptom severity and will provide a urine sample. Samples will be split and initially tested using novel index tests (POCTs) and conventional urinalysis 'dipstick' at the primary care clinic. The second part of the sample will be processed at a National Health Service-based reference laboratory using a modified reference standard including microscopy, microbiological culture, pathogen speciation and antimicrobial susceptibility testing. The UTI reference standard culture, although based on the national methods, is modified to provide accurate bacterial counts, better to define a microbiological diagnosis of UTI. Susceptibility testing will be performed using 'gold-standard' methods, not usually performed in diagnostic laboratories. The primary outcome will be the diagnostic performance (sensitivity, specificity, positive and negative predictive values) of POCTs for detection of UTI and antimicrobial susceptibility for POCTs that include antimicrobial susceptibility testing. Secondary outcomes will include the symptom profile of patients presenting with uncomplicated UTI, a theoretical determination of how use of POCT results might change prescribing, an understanding of POCT failure rate and qualitative capture of the experiences of those using the POCT to deliver the study in primary care clinics., Ethics and Dissemination: Ethical approval was received from the London Central Research Ethics Committee (23/LO/0371) and the UK Health Research Authority. We will publish the findings of The plaTform fOr Urinary tract infection diagnostiC evAluatioN evaluations in peer-reviewed medical journals and more broadly following a dissemination plan formulated by a communications specialist in consultation with patients and the public., Trial Registration Number: ISRCTN80937472., Competing Interests: Competing interests: It is the intention that technology (POCT), associated consumables and training will be provided free of charge to the study under contractual arrangements that preserve the team’s unrestricted rights to publish results. CCB is a member of the Editorial Advisory Board of BMJ Open., (© Author(s) (or their employer(s)) 2025. Re-use permitted under CC BY. Published by BMJ Group.)

Objectives: Cellulitis is often treated with antibiotics for longer than recommended by guidelines. Prolonged therapy may reduce recurrence in certain patients, but it is not known which patients are at greatest risk. Our objective was to develop and temporally validate a risk prediction score to identify patients attending hospital with cellulitis at highest risk of recurrence., Methods: We included UK adult patients with cellulitis attending hospital in an electronic health records (EHR) study to identify demographic, comorbid, physiological, and laboratory factors predicting recurrence (before death) within 90 days, using multivariable logistic regression with backwards elimination in complete cases. A points-based risk score integerised model coefficients for selected predictors. Performance was assessed using the C-index in development and temporal validation samples., Results: The final model included 4938 patients treated for median 8 days (IQR 6-11); 8.8% (n = 436) experienced hospitalisation-associated recurrence. A risk score using eight variables (age, heart rate, urea, platelets, albumin, previous cellulitis, venous insufficiency, and liver disease) ranged from 0-15, with C-index = 0.65 (95%CI: 0.63-0.68). Categorising as low (score 0-1), medium (2-5) and high (6-15) risk, recurrence increased fourfold; 3.2% (95%CI: 2.3-4.4%), 9.7% (8.7-10.8%), and 16.6% (13.3-20.4%). Performance was maintained in the validation sample (C-index = 0.63 (95%CI: 0.58-0.67)). Among patients at high risk, four distinct clinical phenotypes were identified using hierarchical clustering 1) young, acutely unwell with liver disease; 2) comorbid with previous cellulitis and venous insufficiency; 3) chronic renal disease with severe renal impairment; and 4) acute severe illness, with substantial inflammatory responses., Conclusions: Risk of cellulitis recurrence varies markedly according to individual patient factors captured in the Baseline Recurrence Risk in Cellulitis (BRRISC) score. Further work is needed to optimise the score, considering baseline and treatment response variables not captured in EHR data, and establish the utility of risk-based approaches to guide optimal antibiotic duration., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Background and Objective: Point-of-care lateral flow device antigen testing has been used extensively to identify individuals with active SARS-CoV-2 infection in the community. This study aimed to evaluate the diagnostic accuracy of two point-of-care tests (POCTs) for SARS-CoV-2 in routine community care., Methods: Adults and children with symptoms consistent with suspected current COVID-19 infection were prospectively recruited from 19 UK general practices and two COVID-19 testing centres between October 2020 and October 2021. Participants were tested by trained healthcare workers using at least one of two index POCTs (Roche-branded SD Biosensor Standard™ Q SARS-CoV-2 Rapid Antigen Test and/or BD Veritor™ System for Rapid Detection of SARS-CoV-2). The reference standard was laboratory triplex reverse transcription quantitative PCR (RT-PCR) using a combined nasal/oropharyngeal swab. Diagnostic accuracy parameters were estimated, with 95% confidence intervals (CIs), overall, in relation to RT-PCR cycle threshold and in pre-specified subgroups., Results: Of 663 participants included in the primary analysis, 39.2% (260/663, 95% CI 35.5% to 43.0%) had a positive RT-PCR result. The SD Biosensor POCT had sensitivity 84.0% (178/212, 78.3% to 88.6%) and specificity 98.5% (328/333, 96.5% to 99.5%), and the BD Veritor POCT had sensitivity 76.5% (127/166, 69.3% to 82.7%) and specificity 98.8% (249/252, 96.6% to 99.8%) compared with RT-PCR. Sensitivity of both devices dropped substantially at cycle thresholds ≥30 and in participants more than 7 days after onset of symptoms., Conclusions: Both POCTs assessed exceed the Medicines and Healthcare products Regulatory Agency target product profile's minimum acceptable specificity of 95%. Confidence intervals for both tests include the minimum acceptable sensitivity of 80%. In symptomatic patients, negative results on these two POCTs do not preclude the possibility of infection. Tests should not be expected to reliably detect disease more than a week after symptom onset, when viral load may be reduced., Registration: ISRCTN142269., Competing Interests: We have read the journal’s policy and the authors of this manuscript have the following competing interests: The authorship declares funding support for this study from the University of Oxford Medical Sciences Division Benefactors Urgent COVID-19 Fund, the National Institute for Health and Care (NIHR) School of Primary Care Research, and Urgent Public Health funding for the CONDOR Platform from the NIHR and Asthma+Lung UK. The RAPTOR-C19 study team received analysers and assays free of charge from Becton Dickinson for evaluation in this study. GNH declares funding from the National Institute for Health and Care Research (NIHR) paid to the University of Oxford. KD declares grant funding from Alere Inc and Cepheid Inc paid to her institution for unrelated research. TRF declares NIHR support from the NIHR Community Healthcare MIC for diagnostic evaluation research. AJW declares grant funding received by the University of Oxford through a Wellcome Trust Enriching Engagement grant which has supported unrelated patient participation work carried out by the Royal College of General Practitioners Research Surveillance Centre (based at the University of Oxford) for surveillance work. GE declares funding support from the NIHR Community Healthcare MIC recieved by the University of Oxford. AM declares the support of a Wellcome Trust Doctoral Research Fellowship and an NIHR In-practice Fellowship unrelated to this research. PJT declares support from the NIHR Community Healthcare MIC for diagnostic evaluation research. PJT has provided expert support to the Longitude Prize AMR competition administration which is unrelated to this project and for which the University of Oxford received an honorarium. RB declares grant funding for this project from the NIHR and Asthma+Lung UK, with additional funding from the Department of Health and Social Care paid to his host institution. RB declares grants from Siemens Healthineers, Abbott Point-of-Care and Ancon, all paid to his institution for unrelated research. He declares consulting fees received by his institution from Roche, Siemens, Aptamer Group, LumiraDx, Beckman Coulter and Radiometer, with personal fees received from Psyros Diagnostics. RB has received support for attending meetings / travel from Roche and EMCREG International. RB has participated on data safety monitoring boards or advisory boards for the unrelated FORCE Trial, REWIRE Trial, TARGET-CTA, and Magnetocardiography study (MAGNETIC - sponsored by Creavo). RB is the Deputy National Specialty Lead for Trauma & Emergency Care, National Institute for Health and Care Research Clinical Research Network. RB declares receipt of donated reagents for research not detailed in this paper from Roche, LumiraDx, BD, iXensor, Abbott Point-of-Care, Randox, Avacta, Menarini, loan of analysers from Randox and Menarini, and assays run free of charge for research purposes by Chronomics, My110, and Ancon. JJL declares funding from an NIHR Doctoral Research Fellowship which is unrelated to this research. LM declares support from the NIHR Community Healthcare MIC and other NIHR grants to the University of Oxford in support of this work. EL declares unrelated project funding received by the UKHSA Vaccine Evaluation Unit for contract research from GSK, Pfizer and Sanofi. MZ declares her unpaid activities as the Chair of the charitable organisation ISIRV and her membership of the UK SAGE, NERVTAG and JCVI groups. This does not alter our adherence to PLOS ONE policies on sharing data and materials., (Copyright: © 2023 Nicholson et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Microscopy is the gold standard for malaria diagnosis but is dependent on trained personnel. Rapid diagnostic tests (RDTs) form the mainstay of diagnosis in endemic areas without access to high-quality microscopy. We aimed to evaluate whether RDT alone could rule out imported malaria in children presenting to UK emergency departments (EDs)., Methods: UK-based, multi-center, retrospective, diagnostic accuracy study. Included: any child <16 years presenting to ED with history of fever and travel to a malaria-endemic country, between 01/01/2016 and 31/12/2017. Diagnosis: microscopy for malarial parasites (clinical reference standard) and RDT (index test). UK Health Research Authority approval: 20/HRA/1341., Results: There were 47 cases of malaria out of 1,414 eligible cases (prevalence 3.3%) in a cohort of children whose median age was 4 years (IQR 2-9), of whom 43% were female. Cases of Plasmodium falciparum totaled 36 (77%, prevalence 2.5%). The sensitivity of RDT alone to detect malaria infection due to any Plasmodium species was 93.6% (95% CI 82.5-98.7%), specificity 99.4% (95% CI 98.9-99.7%), positive predictive value 84.6% (95% CI 71.9-93.1%) and negative predictive value 99.8% (95% CI 99.4-100.0%). Sensitivity of RDT to detect P. falciparum infection was 100% (90.3-100%), specificity 98.8% (98.1-99.3%), positive predictive value 69.2% (54.9-81.2%, n = 46/52) and negative predictive value 100% (99.7-100%, n = 1,362/1,362)., Conclusions: RDTs were 100% sensitive in detecting P. falciparum malaria. However, lower sensitivity for other malaria species and the rise of pfhrp2 and pfhrp3 (pfhrp2/3) gene deletions in the P. falciparum parasite mandate the continued use of microscopy for diagnosing malaria., (© The Author(s) 2023. Published by Oxford University Press on behalf of The Journal of the Pediatric Infectious Diseases Society.)

Improving prescribing antibiotics appropriately for respiratory infections in primary care is an antimicrobial stewardship priority. There is limited evidence to support interventions to reduce prescribing antibiotics in out-of-hours (OOH) primary care. Herein, we report a service innovation where point-of-care C-Reactive Protein (CRP) machines were introduced to three out-of-hours primary care clinical bases in England from August 2018-December 2019, which were compared with four control bases that did not have point-of-care CRP testing. We undertook a mixed-method evaluation, including a comparative interrupted time series analysis to compare monthly antibiotic prescription rates between bases with CRP machines and those without, an analysis of the number of and reasons for the tests performed, and qualitative interviews with clinicians. Antibiotic prescription rates declined during follow-up, but with no clear difference between the two groups of out-of-hours practices. A single base contributed 217 of the 248 CRP tests performed. Clinicians reported that the tests supported decision making and communication about not prescribing antibiotics, where having 'objective' numbers were helpful in navigating non-prescribing decisions and highlighted the challenges of training a fluctuant staff group and practical concerns about using the CRP machine. Service improvements to reduce prescribing antibiotics in out-of-hours primary care need to be developed with an understanding of the needs and context of this service.

Background: In diagnostic evaluation, it is necessary to assess the clinical impact of a new diagnostic as well as its diagnostic accuracy. The comparative interrupted time series design has been proposed as a quasi-experimental approach to evaluating interventions. We show how it can be used in the design of a study to evaluate a point-of-care diagnostic test for C-reactive protein in out-of-hours primary care services, to guide antibiotic prescribing among patients presenting with possible respiratory tract infection. This study consisted of a retrospective phase that used routinely collected monthly antibiotic prescribing data from different study sites, and a prospective phase in which antibiotic prescribing rates were monitored after the C-reactive protein diagnostic was introduced at some of the sites., Methods: Of 8 study sites, 3 were assigned to receive the diagnostic and 5 were assigned as controls. We obtained retrospective monthly time series of respiratory tract targeted antibiotic prescriptions at each site. Separate ARIMA models at each site were used these to forecast monthly prescription counts that would be expected in the prospective phase, using simulation to obtain a set of 1-year predictions alongside their standard errors. We show how these forecasts can be combined to test for a change in prescription rates after introduction of the diagnostic and estimate power to detect this change., Results: Fitted time series models at each site were stationary and showed second-order annual seasonality, with a clear December peak in prescriptions, although the timing and extent of the peak varied between sites and between years. Mean one-year predictions of antibiotic prescribing rates based on the retrospective time series analysis differed between sites assigned to receive the diagnostic and those assigned to control. Adjusting for the trend in the retrospective time series at each site removed these differences., Conclusions: Quasi-experimental designs such as comparative interrupted time series can be used in diagnostic evaluation to estimate effect sizes before conducting a full randomised controlled trial or if a randomised trial is infeasible. In multi-site studies, existing retrospective data should be used to adjust for underlying differences between sites to make outcome data from different sites comparable, when possible., (© 2022. The Author(s).)

Introduction: Point of care blood testing to aid diagnosis is becoming increasingly common in acute ambulatory settings and enables timely investigation of a range of diagnostic markers. However, this testing allows scope for errors in the pre-analytical phase, which depends on the operator handling and transferring specimens correctly. The extent and nature of these pre-analytical errors in clinical settings has not been widely reported., Methods: We carried out a convergent parallel mixed-methods service evaluation to investigate pre-analytical errors leading to a machine error reports in a large acute hospital trust in the UK. The quantitative component comprised a retrospective analysis of all recorded error codes from Abbott Point of Care i-STAT 1, i-STAT Alinity and Abbott Rapid Diagnostics Afinion devices to summarise the error frequencies and reasons for error, focusing on those attributable to the operator. The qualitative component included a prospective ethnographic study and a secondary analysis of an existing ethnographic dataset, based in hospital-based ambulatory care and community ambulatory care respectively., Results: The i-STAT had the highest usage (113,266 tests, January 2016-December 2018). As a percentage of all tests attempted, its device-recorded overall error rate was 6.8% (95% confidence interval 6.6% to 6.9%), and in the period when reliable data could be obtained, the operator-attributable error rate was 2.3% (2.2% to 2.4%). Staff identified that the most difficult step was the filling of cartridges, but that this could be improved through practice, with a perception that cartridge wastage through errors was rare., Conclusions: In the observed settings, the rate of errors attributable to operators of the primary point of care device was less than 1 in 40. In some cases, errors may lead to a small increase in resource use or time required so adequate staff training is necessary to prevent adverse impact on patient care., Competing Interests: The project was supported by a grant from a commercial source (Becton, Dickinson and Company). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. This does not alter our adherence to PLOS One policies on sharing data and materials.

Background: Serious infections in older people are associated with unplanned hospital admissions and high mortality. Recognising the presence of a serious infection and making an accurate diagnosis are important challenges for General Practice. This study aimed to explore the issues UK GPs face when diagnosing serious infections in older patients., Methods: Qualitative study using semi-structured interviews. 28 GPs from 27 practices were purposively sampled from across the UK to achieve maximum variation in terms of GP role, experience and practice population. Interviews began by asking participants to describe recent or memorable cases where they had assessed older patients with suspected serious infections. Additional questions from the topic guide were used to explore the challenges further. Interview transcripts were coded and analysed using a modified framework approach., Results: Diagnosing serious infection in older adults was perceived to be challenging by participating GPs and the diagnosis was often uncertain. Contributing factors included patient complexity, atypical presentations, as well as a lack of knowledge of patients due to a loss in continuity. Diagnostic challenges were present at each stage of the patient assessment. Scoring systems were mainly used as communication tools. Investigations were sometimes used to resolve diagnostic uncertainty, but availability and speed of result limited their practical use. Clear safety-net plans shared with patients and their families helped GPs manage ongoing uncertainty., Conclusions: Diagnostic challenges are present throughout the assessment of an older adult with a serious infection in primary care. Supporting GPs to provide continuity of care may improve the recognition and developing point of care testing for use in community settings may reduce diagnostic uncertainty.

Background: Accurate assessment of the need for admission is challenging in out-of-hours (OOH) primary care. Understanding more about patient contacts where the decision to continue care in the community may have been incorrect could assist clinicians in assessing clinical risk., Aim: To define the population contacting OOH primary care who are at higher risk of re-presenting to this service and requiring urgent transfer to secondary care within 3 days of their initial contact., Design and Setting: Retrospective service evaluation of 4 years of patient contacts with Oxfordshire OOH primary care., Method: Multivariable logistic regression was used to evaluate demographic and service delivery factors associated with increased risk of delayed escalation to secondary care., Results: Almost 1% of 496 931 patients contacting OOH primary care required escalation to secondary care within 3 days. Of these, 68.5% were initially discharged with no follow-up or advice to contact their GP; 14.7% were initially referred to secondary care. The odds of requiring escalation were increased with age (odds ratio [OR] 1.010; 95% confidence interval [CI] = 1.009 to 1.011; P<0.001), more frequent prior use of the OOH service (OR 1.016; 95% CI = 1.010 to 1.021; P<0.001), and presenting during periods of low call volume (OR 0.880; 95% CI = 0.857 to 0.904; P<0.001)., Conclusion: Older, prior users of the service, presenting at less busy times, are at greater risk of requiring secondary care referral from the OOH service within 3 days of their initial contact. These higher-risk patient groups might benefit from active follow-up by the OOH service., (© British Journal of General Practice 2017.)