Imperial College London

DrBethanDavies

Faculty of MedicineSchool of Public Health

Clinical Senior Lecturer in Epidemiology
 
 
 
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Contact

 

+44 (0)20 7594 3464bethan.davies06

 
 
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Location

 

Medical SchoolSt Mary's Campus

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Summary

 

Publications

Publication Type
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28 results found

Wilson J, Wallace H, Loftus-Keeling M, Ward H, Davies B, Vargas-Palacios A, Hulme C, Wilcox Met al., 2021, Swab-yourself trial with economic monitoring and testing for infections collectively (SYSTEMATIC): Part 1. A diagnostic accuracy, and cost-effectiveness, study comparing clinician-taken versus self-taken rectal and pharyngeal samples for the diagnosis of gonorrhoea and chlamydia, Clinical Infectious Diseases, Vol: 73, Pages: e3172-e3180, ISSN: 1058-4838

BackgroundUrogenital testing misses extragenital Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT). Extragenital self-sampling is frequently undertaken despite no robust RCT evidence of efficacy. We compared clinician-taken rectal and pharyngeal samples with self-taken samples for diagnostic accuracy and cost in MSM and females.MethodsProspective, convenience, sample in UK sexual health clinic. Randomised order of clinician and self-samples from pharynx and rectum, plus first catch urine (MSM) and vulvovaginal swabs (females), for NG/CT detection.ResultsOf 1793 participants (1284 females, 509 MSM), 116 had NG detected (75 urogenital site, 83 rectum, 72 pharynx); 9.4% infected females and 67.3% MSM were urogenital negative. 276 had CT detected (217 urogenital site, 249 rectum, 63 pharynx); 13.1% infected females and 71.8% MSM were urogenital negative. Sexual history did not identify those with rectal infections. Clinician-rectal and self-rectal positive percent agreements (PPA) for NG detection were 92.8% and 97.6%; clinician-rectal, and self-rectal PPA for CT detection were 95.6% and 97.2%. There was no difference in diagnostic accuracy between clinician and self-taken samples.Clinicians performed swabs quicker than participants so costs were lower. However, in asymptomatic people, non-qualified clinicians would oversee self-swabbing and these costs would be lower than clinician’s.ConclusionsThere was no difference in diagnostic accuracy of clinician compared with self-taken extragenital samples. Sexual history did not identify those with rectal infections so individuals should have extragenital clinician, or self-taken, samples. Clinician swabs cost less than self-swabs but in asymptomatic people, or doing home testing, their costs would be lower than clinician swabs.

Journal article

Rashid T, Bennett J, Paciorek C, Doyle Y, Pearson-Stuttard J, Flaxman S, Fecht D, Toledano M, Li G, Daby H, Johnson E, Davies B, Ezzati Met al., 2021, Life expectancy and risk of death in 6,791 English communities from 2002 to 2019: high-resolution spatiotemporal analysis of civil registration data, The Lancet Public Health, Vol: 6, Pages: e805-e816, ISSN: 2468-2667

Background: There is limited data with high spatial granularity on how mortality and longevity have changed in English communities. We estimated trends from 2002 to 2019 in life expectancy and probabilities of death at different ages for all 6,791 English middle-layer super output areas (MSOAs).Methods: We used de-identified data for all deaths in England from 2002 to 2019 with information on age, sex and MSOA of residence, and population counts by age, sex and MSOA. We used a Bayesian hierarchical model to obtain estimates of age-specific death rates by sharing information across age groups, MSOAs and years. We used life table methods to calculate life expectancy at birth and probabilities of death in different ages by sex and MSOA.Results: In 2002-2006 and 2006-2010, the vast majority of MSOAs experienced a life expectancy increase for both sexes. In 2010-2014, female life expectancy decreased in 351 (5%) of MSOAs. By 2014-2019, the number of MSOAs with declining life expectancy was 1,270 (19%) for women and 784 (12%) for men. The life expectancy increase from 2002 to 2019 was smaller where life expectancy had been lower in 2002, mostly northern urban MSOAs, and larger where life expectancy had been higher in 2002, mostly MSOAs in and around London. As a result of these trends, the gap between the 1st and 99th percentiles of MSOA life expectancy for women increased from 10.7 (95% credible interval 10.4-10.9) in 2002 to reach 14.2 (13.9-14.5) years in 2019, and from 11.5 (11.3-11.7) years to 13.6 (13.4-13.9) years for men. Interpretation: In many English communities, life expectancy declined in the years prior to the Covid-19 pandemic. To ensure that this trend does not continue there is a need for pro-equity economic and social policies, and greater investment on public health and healthcare.

Journal article

Davies B, Araghi M, Moshe M, Gao H, Bennet K, Jenkins J, Atchison C, Darzi A, Ashby D, Riley S, Barclay W, Elliott P, Ward H, Cooke Get al., 2021, Acceptability, usability and performance of lateral flow immunoassay tests for SARS-CoV-2 antibodies: REACT-2 study of self-testing in non-healthcare key workers, Open Forum Infectious Diseases, ISSN: 2328-8957

Background Seroprevalence studies are essential to understand the epidemiology of SARS-CoV-2. Various technologies, including laboratory assays and point-of-care self-tests, are available for antibody testing. The interpretation of seroprevalence studies requires comparative data on the performance of antibody tests. Methods In June 2020, current and former members of the UK Police forces and Fire service performed a self-test lateral flow immunoassay (LFIA), had a nurse-performed LFIA and provided a venous blood sample for ELISA . We present the prevalence of antibodies to SARS-CoV-2; the acceptability and usability of self-test LFIAs; and determine the sensitivity and specificity of LFIAs compared to laboratory ELISA. Results In this cohort of 5189 current and former members of the Police service and 263 members of the Fire service, 7.4% (396/5,348; 95% CI, 6.7-8.1) were antibody positive. Seroprevalence was 8.9% (6.9-11.4) in those under 40 years, 11.5% (8.8-15.0) in those of non-white ethnicity and 7.8% (7.1-8.7) in those currently working. Self-test LFIA had an acceptability of 97.7% and a usability of 90.0%. There was substantial agreement between within-participant LFIA results (kappa 0.80; 0.77-0.83). The LFIAs had a similar performance: compared to ELISA, sensitivity was 82.1% (77.7-86.0) self-test and 76.4% (71.9-80.5) nurse-performed with specificity of 97.8% (97.3-98.2) and 98.5% (98.1-98.8) respectively. Conclusion A greater proportion of this non-healthcare key worker cohort showed evidence of previous infection with SARS-CoV-2 than the general population at 6.0% (5.8-6.1) following the first wave in England. The high acceptability and usability reported by participants and similar performance of self-test and nurse-performed LFIAs indicate that the self-test LFIA is fit for purpose for home-testing in occupational and community prevalence studies.

Journal article

Davies B, Araghi M, Moshe M, Gao H, Bennet K, Jenkins J, Atchison C, Darzi A, Ashby D, Riley S, Barclay W, Elliott P, Ward H, Cooke Get al., 2021, Acceptability, usability and performance of lateral flow immunoassay tests for SARSCoV-2 antibodies: REACT-2 study of self-testing in non-healthcare key workers, Publisher: Cold Spring Harbor Laboratory

BackgroundSeroprevalence studies in key worker populations are essential to understand the epidemiology of SARS-CoV-2. Various technologies, including laboratory assays and pointof-care self-tests, are available for antibody testing. The interpretation of seroprevalence studies requires comparative data on the performance of antibody tests.MethodsIn June 2020, current and former members of the UK Police forces and Fire service performed a self-test lateral flow immunoassay (LFIA) and provided a saliva sample, nasopharyngeal swab, venous blood samples for Abbott ELISA and had a nurse performed LFIA. We present the prevalence of PCR positivity and antibodies to SARS-CoV-2 in this cohort following the first wave of infection in England; the acceptability and usability of selftest LFIAs (defined as use of the LFIA kit and provision of a valid result, respectively); and determine the sensitivity and specificity of LFIAs compared to laboratory ELISAs.ResultsIn this cohort of non-healthcare key workers, 7.4% (396/5,348; 95% CI, 6.7-8.1) were antibody positive. Seroprevalence was 8.9% (6.9-11.4) in those under 40 years, 11.5% (8.8-15.0) in those of non-white British ethnicity and 7.8% (7.1-8.7) in those currently working.The self-test LFIA had an acceptability of 97.7% and a usability of 90.0%. There was substantial agreement between within-participant LFIA results (kappa 0.80; 0.77-0.83). The LFIAs (self-test and nurse-performed) had a similar performance: compared to ELISA, sensitivity was 82.1% (77.7-86.0) self-test and 76.4% (71.9-80.5) nurse-performed with specificity of 97.8% (97.3-98.2) and 98.5% (98.1-98.8) respectively.ConclusionA greater proportion of the non-healthcare key worker cohort showed evidence of previous infection with SARS-CoV-2 than the general population at 6.0% (5.8-6.1) following the first wave in England. The high acceptability and usability reported by participants and the similar performance of self-test and nurse-performed LFIAs indicate that t

Working paper

Davies B, Parkes B, Bennett J, Fecht D, Blangiardo M, Ezzati M, Elliott Pet al., 2021, Community factors and excess mortality in first wave of the COVID-19 pandemic in England, Nature Communications, ISSN: 2041-1723

Risk factors for increased risk of death from Coronavirus Disease 19 (COVID-19) have been identified but less is known on characteristics that make communities resilient or vulnerable to the mortality impacts of the pandemic. We applied a two-stage Bayesian spatial model to quantify inequalities in excess mortality at the community level during the first wave of the pandemic in England. We used geocoded data on all deaths in people aged 40 years and older during March-May 2020 compared with 2015-2019 in 6,791 local communities. Here we show that communities with an increased risk of excess mortality had a high density of care homes, and/or high proportion of residents on income support, living in overcrowded homes and/or high percent of people with a non-White ethnicity (including Black, Asian and other minority ethnic groups). Conversely, after accounting for other community characteristics, we found no association between population density or air pollution and excess mortality. Overall, the social and environmental variables accounted for around 15% of the variation in mortality at community level. Effective and timely public health and healthcare measures that target the communities at greatest risk are urgently needed if England and other industrialised countries are to avoid further widening of inequalities in mortality patterns as the pandemic progresses.

Journal article

Konstantinoudis G, Padellini T, Bennett J, Davies B, Ezzati M, Blangiardo Met al., 2021, Response to "Re: Long-term exposure to air-pollution and COVID-19 mortality in England: A hierarchical spatial analysis", ENVIRONMENT INTERNATIONAL, Vol: 150, ISSN: 0160-4120

Journal article

Matthews NR, Davies B, Ward H, 2020, Global health education in UK medical schools: a review of undergraduate university curricula, BMJ Global Health, Vol: 5, Pages: 1-12, ISSN: 2059-7908

IntroductionIn recognition of our increasingly globalised world, global health is now arequired component of the medical school curriculum in the UK. We reviewthe current provision of global health education (GHE) in UK medical schoolsto identify gaps in compulsory teaching.MethodsWe conducted a review of the literature to inform a two-part electronic surveyof global health compulsory teaching, optional teaching and pre-electivetraining. Surveys were sent to all 33 UK medical schools for completion by thefaculty lead on global health and the nominated final year studentrepresentative.ResultsSurveys were returned by 29 (88%) medical school faculty and 15 (45%)medical student representatives; 24 (83%) faculty and 10 (67%) studentsreported including GHE in the core curriculum, however, there was widevariation in learning outcomes covered. On average 75% of faculty and 82%of students reported covering recommended global health themes ‘Globalburden of disease’, ‘Socioeconomic and environmental determinants ofhealth’, Human rights and ethics’, and ‘Cultural diversity and health’, whilstonly 48% of faculty and 33% of students reported teaching on ‘Healthsystems’ and ‘Global health governance’. Almost all institutions offeredoptional global health programmes and most offered some form of preelective training, although content and delivery were variable.ConclusionOver the last decade, the inclusion of global health in the core curriculum ofUK medical schools has increased dramatically. Yet, despite interest amongststudents, significant gaps are apparent in current GHE. Governing bodies inmedical education should establish a comprehensive national strategy to helpimprove access to fundamental GHE for all medical students.

Journal article

Konstantinoudis G, Padellini T, Bennett J, Davies B, Ezzati M, Blangiardo Met al., 2020, Long-term exposure to air-pollution and COVID-19 mortality in England: a hierarchical spatial analysis, Environment International, ISSN: 0160-4120

Journal article

Wilson JD, Wallace HE, Loftus-Keeling M, Ward H, Davies B, Vargas-Palacios A, Hulme C, Wilcox MHet al., 2020, Swab-yourself trial with economic monitoring and testing for infections collectively (SYSTEMATIC): Part 2. A diagnostic accuracy, and cost-effectiveness, study comparing rectal, pharyngeal and urogenital samples analysed individually, versus as a pooled specimen, for the diagnosis of gonorrhoea and chlamydia., Clin Infect Dis

BACKGROUND: Sexual history does not accurately identify those with extragenital Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) so universal extragenital sampling is recommended. Nucleic acid amplification tests (NAATs) are expensive. If urogenital, plus rectal and pharyngeal, samples are analysed the diagnostic cost is trebled. Pooling samples into one NAAT container would cost the same as urogenital samples alone. We compared clinician triple samples analysed individually with self-taken pooled samples for diagnostic accuracy, and cost, in MSM and females. METHODS: Prospective, convenience, sample in UK sexual health clinic. Randomised order of clinician and self-samples from pharynx, rectum, plus first catch urine (FCU) in MSM and vulvovaginal swabs (VVS) in females, for NG and CT detection. RESULTS: Of 1793 participants (1284 females, 509 MSM), 116 had NG detected (75 urogenital, 83 rectum, 72 pharynx). 276 had CT detected (217 urogenital, 249 rectum, 63 pharynx).There was no difference in sensitivities between clinician triple samples and self-pooled specimens for NG (99.1%, 98.3%) but clinician samples analysed individually identified 3% more chlamydia infections than pooled (99.3%, 96.0%; p=0.027). However, pooled specimens identified more infections than VVS/FCU alone. Pooled specimens missed 2 NG and 11 CT infections, whereas VVS/FCU missed 41 NG and 58 CT infections. Self-taken pooled specimens were the most cost-effective. CONCLUSIONS: Just FCU/VVS testing missed many infections. Self-taken pooled samples were as sensitive as clinician triple samples for identifying NG, but clinician samples analysed individually identified 3% more CT infections than pooled. The extragenital sampling was achievable at no additional diagnostic cost to the FCU/VVS. TRIAL REGISTRATION: ClinicalTrials.gov NCT02371109.

Journal article

Bruton J, Jones K, Jenkins R, Davies B, Ward H, Toledano Met al., 2020, Enabling participation of Black and Minority Ethnic (BME) and seldom-heard communities in health research: A case study from the SCAMP adolescent cohort study, Research for All, Vol: 4, Pages: 207-219, ISSN: 2399-8121

Aim: To investigate barriers and facilitators to BME parental consent for children’s involvement in data-sharing aspects of study on mobile phone and wireless device use (SCAMP). To co-produce solutions to increase participation. Methods: Focus groups, telephone interviews, community event, PPI Café; symposium with public, participants and researchers. Results: Barriers were concerns about the research, practical constraints, poor communication. Facilitators were value of research, benefits to others. Solutions to increase participation were community support and clear, simple communication. Overall, trust in the research and the researchers was a key focus of enabling participation.Sharing recommendations: Symposium generated ideas about improving participation including tailoring participant information, engaging with local advocates, involving people in research design and delivery.Key words: Seldom heard, BME, research participation, co-production, PPI, parental consent

Journal article

Luna Puerta L, Kendall W, Davies B, Day S, Ward Het al., 2020, The reported impact of public involvement in biobanks: a scoping review, Health Expectations, Vol: 23, ISSN: 1369-6513

BackgroundBiobanks increasingly employ public involvement and engagement strategies, though few studies have explored their impact. This review aims to (a) investigate how the impact of public involvement in biobanks is reported and conceptualized by study authors; in order to (b) suggest how the research community might re‐conceptualize the impact of public involvement in biobanks.MethodsA systematic literature search of three electronic databases and the INVOLVE Evidence Library in January 2019. Studies commenting on the impact of public involvement in a biobank were included, and a narrative review was conducted.Results and discussionForty‐one studies covering thirty‐one biobanks were included, with varying degrees of public involvement. Impact was categorized according to where it was seen: ‘the biobank’, ‘people involved’ and ‘the wider research community’. Most studies reported involvement in a ‘functional’ way, in relation to improved rates of participation in the biobank. Broader forms of impact were reported but were vaguely defined and measured. This review highlights a lack of clarity of purpose and varied researcher conceptualizations of involvement. We pose three areas for further research and consideration by biobank researchers and public involvement practitioners.ConclusionsFunctional approaches to public involvement in biobanking limit impact. This conceptualization of involvement emerges from an entrenched technical understanding that ignores its political nature, complicated by long‐standing disagreement about the values of public involvement. This study urges a re‐imagination of impact, re‐conceptualized as a two‐way learning process. More support will help researchers and members of the public to undergo such reflective exercises.

Journal article

Ensor S, Davies B, Rai T, Ward Het al., 2019, The effectiveness of demand creation interventions for voluntary male medical circumcision for HIV prevention in Sub-Saharan Africa; a mixed methods systematic review, Journal of the International AIDS Society, Vol: 22, Pages: 40-53, ISSN: 1758-2652

IntroductionUNAIDS has recommended that in 14 countries across sub‐Saharan Africa (SSA), 90% of men aged 10 to 29 years should be circumcised by 2021 to help reduce transmission of HIV. To achieve this target demand creation programmes have been widely implemented to increase demand for Voluntary Medical Male Circumcision (VMMC). This review explores the effectiveness of demand creation interventions and factors affecting programme implementation.MethodsWe completed a mixed methods systematic review searching Medline, Embase, Global health, psycINFO and CINAHL databases in August 2018 with no time restrictions. Demand creation interventions conducted in SSA were categorized and quantitative data about VMMC uptake was used to compare relative and absolute effectiveness of interventions. Qualitative data were summarized into themes relevant to the delivery and impact of programmes.Results and discussionEighteen of the 904 titles were included in the review. Effective interventions were identified in each demand creation category: financial incentives, counselling or education, involvement of influencers and novel information delivery. Of the 11 randomized controlled trials (RCTs), the greatest absolute impact on VMMC prevalence was seen with a complex intervention including VMMC promotion training for religious leaders (compared to control: 23% (95% CI 22.8 to 23.8) absolute increase; odds ratio (OR) 3.2 (1.4 to 7.3)). Financial incentives generally produced the largest relative effects with men up to seven‐times more likely to undergo VMMC in the intervention arm compared to control (adjusted OR 7.1 (95% CI 2.4 to 20.8), 7.1% (3.7 to 10.5) absolute increase). Qualitative findings suggest that interventions are more impactful when they are judged appropriate and acceptable by the target population; delivered by people with relevant personal experience; and addressing broader social and cultural influences through partnership with and education of community leaders.Con

Journal article

Papageorgiou V, Crittendon E, Davies B, Ward Het al., 2019, Impact of pre-exposure prophylaxis on the risk of bacterial sexually transmitted infections among cisgender women: systematic review, AIDS Impact 2019

Conference paper

Ronn M, Mc Grath-Lone L, Davies B, Wilson J, Ward Het al., 2019, Evaluation of the performance of nucleic acid amplification tests (NAATs) in detection of chlamydia and gonorrhoea infection in vaginal specimens relative to patient infection status: a systematic review, BMJ Open, Vol: 9, ISSN: 2044-6055

OBJECTIVE: We aimed to assess the performance of NAATs using vaginal specimens in comparison to other urogenital specimens in their ability to detect chlamydia and gonorrhea infection in women.DESIGN: Systematic review.DATA SOURCES: EMBASE and Ovid MEDLINE databases through 3 October 2017.ELIGIBILITY CRITERIA FOR SELECTING STUDIES: We included studies that tested samples from the vagina and ≥1 other site (cervix and/or urine) with ≥2 NAATs for chlamydia and ≥2 NAATs or 1 NAAT and culture for gonorrhoea for each site.DATA EXTRACTION AND SYNTHESIS: We compared the performance of NAATs on specimens taken from the vagina to those from the cervix or urine in diagnosing chlamydia and gonorrhoea infection in women based on patient infection status (PIS). We analysed the performance using vaginal specimens compared to PIS. Performance is defined as the sensitivity of a NAAT using a specimen site and PIS status of the patient. We assessed risk of bias using modified QUADAS-2.RESULTS: Nine publications met the inclusion criteria (eight for chlamydia; six for gonorrhoea) and were narratively reviewed. Pooled summary estimates were not calculated due to the variable methodology and PIS definitions. Tests performed on vaginal specimens accomplished similar performance to cervical and urine specimens for chlamydia (range of performance estimates: vaginal 65-100%, cervical 59-97%, urine 57-100%) and gonorrhoea (vaginal 64-100%, cervical 85-100%, urine 67-94%). Vaginal specimens were estimated to have a performance >80% for chlamydia and gonorrhoea infections in all but one study.CONCLUSIONS: Performance of the NAATs for chlamydia and gonorrhea detection using vaginal specimens was similar to that of cervical and urine specimens relativeto PIS. As vaginal samples have a higher acceptability and lower cost, the study can support clinical testing guidelines by providing evidence that vaginal samples are a suitable alternative to traditional test sites.

Journal article

Beardon S, Patel K, Davies B, Ward Het al., 2018, Informal Carers' Perspectives on the Delivery of Acute Hospital Care for Patients with Dementia: A Systematic Review, BMC Geriatrics, Vol: 23, ISSN: 1471-2318

Background: Providing high quality acute hospital care for patients with dementia is an increasing challenge asthe prevalence of the disease rises. Informal carers of people with dementia are a critical resource for improvinginpatient care, due to their insights into patients’ needs and preferences. We summarise informal carers’ perspectives ofacute hospital care to inform best practice service delivery.Methods: We conducted a systematic search of bibliographic databases and sought relevant grey literature. We usedthematic synthesis analysis to assimilate results of the studies and describe components of care that influence perceivedquality.Results: Twenty papers met the inclusion criteria. Findings identified four overarching components of care thatinfluenced carer experience and their perceptions of care quality: ‘Patient care’, ‘Staff interactions’, ‘Carer’s situation’ and‘Hospital environment’. Need for improvement was identified in staff training, provision of help with personal careneeds, and dignified treatment of patients. Carers need to be informed, involved and supported during hospitaladmission in order to promote the most positive experience.Conclusion: This review identifies common perspectives of informal carers of people with dementia in the acutehospital setting and highlights important areas to address to improve the experience of an admission for both carerand patient.

Journal article

Davies B, Turner KME, Frolund M, Benfield T, Andersen B, Westh H, Ward Het al., 2018, Pelvic inflammatory disease risk following negative results from chlamydia nucleic acid amplification tests (NAATs) versus non-NAATs in Denmark: A retrospective cohort study, PLoS Medicine, Vol: 15, ISSN: 1549-1277

BackgroundNucleic Acid Amplification Tests (NAATs) are the recommended test type for diagnosing Chlamydia trachomatis (chlamydia). However, less sensitive diagnostic methods—including direct immunofluorescence (IF) and enzyme-linked immunoassay (ELISA)—remain in use in lower resourced settings. We estimate the risk of pelvic inflammatory disease (PID) following undiagnosed infection in women tested with non-NAATs and estimate the health gain from using accurate diagnostic tests.Methods and findingsWe used Denmark’s national Chlamydia Study dataset to extract all chlamydia tests performed in women aged 15–34 years (1998–2001). Tests were categorised as non-NAAT (IF/ELISA) or NAAT and limited to each woman’s first test in the study period. We linked test data to hospital presentations for PID within 12 months from the Danish National Patient Register. The study included 272,105 women with a chlamydia test, just under half (44.78%, n = 121,857) were tested using NAATs. Overall, 6.38% (n = 17,353) tested positive for chlamydia and 0.64% (n = 1,732) were diagnosed with PID within 12 months. The risk of PID following a positive chlamydia test did not differ by test type (NAAT 0.81% [95% CI 0.61–1.00], non-NAAT 0.78% [0.59–0.96]). The risk of PID following a negative test was significantly lower in women tested with NAATs compared to non-NAATs (0.55% [0.51–0.59] compared to 0.69% [0.64–0.73]; adjusted odds ratio (AOR) 0.83 [0.75–0.93]). We estimate that 18% of chlamydia infections in women tested with a non-NAAT were undiagnosed and that the risk of progression from undiagnosed chlamydia infection to PID within 12 months was 9.52% (9.30–9.68). Using non-NAATs could lead to an excess 120 cases of PID per 100,000 women tested compared to using NAATs. The key limitations of this study are under ascertainment of PID cases, misclassification bias in chlamydia and PID exposure status, bias to the association

Journal article

Davies B, turner KME, Leung S, Yu BN, Frolund M, Benfield T, Blanchard J, Westh H, Ward Het al., 2017, Comparison of the population excess fraction of chlamydia trachomatis infection on pelvic inflammatory disease at 12-months in the presence and absence of chlamydia testing and treatment: systematic review and retrospective cohort analysis, PLOS One, Vol: 12, ISSN: 1932-6203

Background: The impact of Chlamydia trachomatis (chlamydia) control on the incidence of pelvic inflammatory disease (PID) is theoretically limited by the proportion of PID caused by chlamydia. We estimate the population excess fraction (PEF) of treated chlamydia infection on PID at 12-months in settings with widespread chlamydia control (testing and treatment) and compare this to the estimated PEF of untreated chlamydia. Methods: We used two large retrospective population-based cohorts of women of reproductive age from settings with widespread chlamydia control to calculate the PEF of treated chlamydia on PID at 12-months. We undertook a systematic review to identify further studies that reported the risk of PID in women who were tested for chlamydia (infected and uninfected). We used the same method to calculate the PEF in eligible studies then compared all estimates of PEF. Results: The systematic review identified a single study, a randomised controlled trial of chlamydia screening (POPI-RCT). In the presence of testing and treatment <10% of PID at 12-months was attributable to treated (baseline) chlamydia infections (Manitoba: 8.86%(95%CI 7.15-10.75); Denmark: 3.84%(3.26-4.45); screened-arm POPI-RCT: 0.99%(0.00-29.06)). In the absence of active chlamydia treatment 26.44% (11.57-46.32) of PID at 12-months was attributable to untreated (baseline) chlamydia infections (deferred-arm POPI-RCT). The PEFs suggest that eradicating baseline chlamydia infections could prevent 484 cases of PID at 12-months per 100,000 women in the untreated setting and 13-184 cases of PID per 100,000 tested women in the presence of testing and treatment. Conclusion: Testing and treating chlamydia reduced the PEF of chlamydia on PID by 65% compared to the untreated setting. But in the presence of testing and treatment over 90% of PID could not be attributed to a baseline chlamydia infection. More information is needed about the aetiology of PID to develop effective strategies for impro

Journal article

Chandrasekaran L, Davies B, Eaton J, Ward Het al., 2016, Chlamydia diagnosis rate in England in 2012: an ecological study of local authorities, Sexually Transmitted Infections, Vol: 93, Pages: 226-228, ISSN: 1472-3263

Objectives Local authorities (LAs) in England commission chlamydia screening as part of the National Chlamydia Screening Programme. It is recommended that LAs achieve a chlamydia diagnosis rate of ≥2300 cases per 100 000 population aged 15–24. We describe national patterns in attainment of the chlamydia diagnosis rate recommendation and possible implications of using it to measure LA-level performance.Methods We used publicly available data sets from England (2012) to explore the association between LAs attaining the recommended chlamydia diagnosis rate and population size, socioeconomic deprivation, test setting and sex.Results We used data from 1 197 121 recorded chlamydia tests in females and 564 117 in males. The chlamydia diagnosis rate recommendation was achieved by 22% (72/324) of LAs overall (43% female population; 8% male population). LAs in the highest deprivation quintile were more likely to reach the recommendation than those in the least-deprived quintile for both sexes (women: unadjusted prevalence ratio (UPR) 7.43, 95% CI 3.65 to 15.11; men: UPR 7.00, 95% CI 1.66 to 29.58). The proportion of tests performed in genitourinary medicine clinics was negatively associated with attainment of the recommended diagnosis rate (UPR 0.95, 0.93 to 0.97).Conclusions Chlamydia diagnosis rate recommendations that reflect local area deprivation (as a proxy for disease burden) may be more appropriate than a single national target if the aim is to reduce health inequalities nationally. We suggest LAs monitor their chlamydia diagnosis rate, test coverage and test positivity across a range of measures (including setting and sex) and pre/post changes to commissioned services. Critical evaluation of performance against the recommendation should be reflected in local commissioning decisions.

Journal article

Davies B, Turner K, Frolund M, Ward H, May M, Rasmussen S, Benfield T, Westh H, Danish Chlamydia Study Groupet al., 2016, Risk of reproductive complications following chlamydia testing: a population-based retrospective cohort study in Denmark, Lancet Infectious Diseases, Vol: 16, Pages: 1057-1064, ISSN: 1473-3099

Background: Uncertainty in the risk of reproductive complications (pelvic inflammatory disease (PID), ectopic pregnancy (EP) and tubal factor infertility (TFI)) following chlamydia infection and repeat infection hampers the design of evidence-based chlamydia control programmes. We estimate the association between diagnosed chlamydia and episodes of hospital healthcare (in-patient, out-patient and emergency department) for a reproductive complication.Methods: We constructed and analysed a retrospective population-based cohort of women aged 15-44 years from administrative records in Denmark (1995-2012). Findings: The 516,720 women (103,344 positive, 182,879 negative, 230,497 never-tested) had a mean follow-up of 7.96 years. Compared to women with only negative tests, the risk of each complication was 30% higher in women with ≥1 positive test (adjusted hazard ratios (AHRs) PID 1·50(1·43-1·57); EP 1·31(1·25-1·38); TFI 1·37(1·24-1·52)) and 60% lower in women who were never-tested (AHRs PID 0·33(0·31-0·35); EP 0·42(0·39-0·44); TFI 0·29(0·25-0·33)). A positive test had a minor absolute impact on health as the difference in the lifetime incidence of complications was small between women who tested positive and those who tested negative (PID 0.6%; EP 0.2%; TFI 0·1%). Repeat infections increased the risk of PID by a further 20% (AHR 1·20(1·11-1·31)). Interpretation: A single diagnosed chlamydia infection increased the risk of all complications and a repeat diagnosed infection further increased the risk of PID. Therefore control programmes must prevent first and repeat infections to improve women’s reproductive health.

Journal article

Davies B, Ward H, 2016, A pathway to chlamydia control: updated ECDC guidance, Sexually Transmitted Infections, Vol: 92, Pages: 483-484, ISSN: 1472-3263

In 2009, the European Centre for Disease Prevention and Control (ECDC) published guidance on chlamydia (Chlamydia trachomatis) control in Europe.1 In it we recommended that EU/EEA member states ensure the provision of basic resources and systems (for diagnosis, case and partner management) before embarking on any expanded screening programme. This guidance was based on evidence first that there was a huge variation in availability of clinical services for chlamydia across member states, and second that the evidence for population level programmes was missing.1 ,2 This month ECDC has released updated guidance that we developed with the support of ECDC experts following a programme of work to update the evidence, including an extensive review of the epidemiology and natural history of chlamydia and the clinical and cost-effectiveness of screening programmes.3 The team also repeated the survey of member states, and assessed the impact of the original guidance.4 ,5The survey showed that more countries had established essential diagnostic and management facilities and guidelines;6 it was hard to attribute this …

Journal article

Davies B, Ward H, 2016, Guidance on chlamydia control in Europe 2015, Stockholm, Sweden, Publisher: European Centre for Disease Prevention and Control, TQ-01-16-029-EN-N

Executive summaryThis evidence-based guidance updates the 2009 ECDC Chlamydia control in Europe guidance [5]. It was developed by a technical expert group using evidence gathered by the Chlamydia control in Europe programme of work, which ECDC commissioned in 2011 and presented in three accompanying technical reports in 2014 and 2015. The work included a critical review and update of the scientific evidence on the epidemiology and natural history of chlamydia and the clinical and cost-effectiveness of screening programmes, an update of information aboutchlamydia prevention and control activities in EU/EEA Member States, and a review of the impact of the 2009 ECDC chlamydia control guidance. In 2014, an expert consultation provided in-depth information about the use of the 2009 guidance within countries and made suggestions for the revision of the guidance.The aim of this guidance is to support Member States to develop, implement or improve national or local strategies for chlamydia control. This guidance sets out the current evidence base behind the proposed options, highlights key gaps in knowledge, and suggests effective options for national chlamydia control strategies. It is directedprimarily at policy advisors but should be useful for programme managers and experts in sexual health, especially those at the European or national levels.The evidence-based options presented here should be interpreted and applied according to clinical, epidemiological, healthcare and resource environments: there is marked variation in current chlamydia controlstrategies across EU/EEA Member States which reflects differences in available resources, health priorities and uncertainties in the evidence-base for chlamydia control interventions. The evidence base for primary prevention activities is still deficient but expert opinion is that it is prudent to offer these interventions to all at-risk individuals.Diagnosing and treating cases of chlamydia can improve the health of the affect

Report

Ward H, Davies B, Ronn M, 2015, Chlamydia control in Europe: Qualitative evaluation of the impact of the2009 ECDC guidance document Chlamydia control in Europe, Stockholm, Sweden, Publisher: European Centre for Disease Prevention and Control, TQ-02-15-038-EN-N

In 2011, the European Centre for Disease Prevention and Control (ECDC) commissioned a programme of work to improve knowledge about the impact of chlamydia and chlamydia control in Europe. The aim of this project was to critically review and update the scientific evidence on the epidemiology and natural history of chlamydia and the clinical and cost-effectiveness of screening, update information about chlamydia prevention and control activities in EU/EEA Member States, and review the impact of the 2009 ECDC chlamydia control guidance. This technical report describes the evaluation of the impact of the 2009 guidance document on policymaking in Member States and presents recommendations for a revised version of the guidance. It includes an overview of the responses collected during the 2012 survey on chlamydia control activities in EU/EEA Member States. Different user types – with regard to the guideline document – were identified and described in this report. In addition, a qualitative analysis of the discussions at the March 2014 meeting was conducted. The meeting had brought together experts from Member States who discussed their experiences with the guidance document.This report concludes with evidence-based recommendations for the revision of the 2009 guidance document.

Report

Davies B, 2014, The association between Chlamydia trachomatis and pelvic inflammatory disease: findings from observational studies

Thesis dissertation

Davies B, Ward H, Leung S, Turner KME, Garnett GP, Blanchard JF, Yu BNet al., 2014, Heterogeneity in Risk of Pelvic Inflammatory Diseases After Chlamydia Infection: A Population-Based Study in Manitoba, Canada, Journal of Infectious Diseases, Vol: 210, Pages: S549-S555, ISSN: 1537-6613

Background. The association between chlamydia infection and pelvic inflammatory disease (PID) is a key parameterfor models evaluating the impact of chlamydia control programs. We quantified this association using aretrospective population-based cohort.Methods. We used administrative health data sets to construct a retrospective population-based cohort ofwomen and girls aged 12–24 years who were resident in Manitoba, Canada, between 1992 and 1996. We performedsurvival analysis on a subcohort of individuals who were tested for chlamydia to estimate the risk of PID diagnosed ina primary care, outpatient, or inpatient setting after ≥1 positive chlamydia test.Results. A total of 73 883 individuals contributed 625 621 person years of follow-up. Those with a diagnosis ofchlamydia had an increased risk of PID over their reproductive lifetime compared with those who tested negative(adjusted hazard ratio [AHR], 1.55; 95% confidence interval [CI], 1.43–1.70). This risk increased with each subsequentinfection: the AHR was 1.17 for first reinfection (95% CI, 1.06–1.30) and 1.35 for the second (95% CI,1.04–1.75). The increased risk of PID from reinfection was highest in younger individuals (AHR, 4.55 (95% CI,3.59–5.78) in individuals aged 12–15 years at the time of their second reinfection, compared with individualsolder than 30 years).Conclusions. There is heterogeneity in the risk of PID after a chlamydia infection. Describing the progression toPID in mathematical models as an average rate may be an oversimplification; more accurate estimates of the costeffectivenessof screening may be obtained by using an individual-based measure of risk. Health inequalities may bereduced by targeting health promotion interventions at sexually active girls younger than 16 years and those with ahistory of chlamydia.

Journal article

Davies B, Anderson S-J, Turner KME, Ward Het al., 2014, How robust are the natural history parameters used in chlamydia transmission dynamic models? A systematic review, THEORETICAL BIOLOGY AND MEDICAL MODELLING, Vol: 11

Journal article

Davies B, Turner K, Ward H, 2013, Risk of Pelvic Inflammatory Disease After Chlamydia Infection in a Prospective Cohort of Sex Workers, SEXUALLY TRANSMITTED DISEASES, Vol: 40, Pages: 230-234, ISSN: 0148-5717

Journal article

Saikat S, Kreis I, Davies B, Bridgman S, Kamanyire Ret al., 2013, The impact of PFOS on health in the general population: a review, ENVIRONMENTAL SCIENCE-PROCESSES & IMPACTS, Vol: 15, Pages: 329-335, ISSN: 2050-7887

Journal article

Ward H, Toledano MB, Shaddick G, Davies Bet al., 2012, Oxford Handbook of Epidemiology for Clinicians 978-0-19-852988-0, Oxford UK, Publisher: Oxford University Press, ISBN: 978-0-19-852988-0

Book

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