Exploring how space, time, and sampling impact our ability to measure genetic structure across Plasmodium falciparum populations

A primary use of malaria parasite genomics is identifying highly related infections to quantify epidemiological, spatial, or temporal factors associated with patterns of transmission. For example, spatial clustering of highly related parasites can indicate foci of transmission and temporal differences in relatedness can serve as evidence for changes in transmission over time. However, for infections in settings of moderate to high endemicity, understanding patterns of relatedness is compromised by complex infections, overall high forces of infection, and a highly diverse parasite population. It is not clear how much these factors limit the utility of using genomic data to better understand transmission in these settings. In particular, further investigation is required to determine which patterns of relatedness we expect to see with high quality, densely sampled genomic data in a high transmission setting and how these observations change under different study designs, missingness, and biases in sample collection. Here we investigate two identity-by-state measures of relatedness and apply them to amplicon deep sequencing data collected as part of a longitudinal cohort in Western Kenya that has previously been analysed to identify individual-factors associated with sharing parasites with infected mosquitoes. With these data we use permutation tests, to evaluate several hypotheses about spatiotemporal patterns of relatedness compared to a null distribution. We observe evidence of temporal structure, but not of fine-scale spatial structure in the cohort data. To explore factors associated with the lack of spatial structure in these data, we construct a series of simplified simulation scenarios using an agent based model calibrated to entomological, epidemiological and genomic data from this cohort study to investigate whether the lack of spatial structure observed in the cohort could be due to inherent power limitations of this analytical method. We further investigate how our hypothesis testing behaves under different sampling schemes, levels of completely random and systematic missingness, and different transmission intensities.

In a large dataset of primary care patients, use of CHA2DS2-VA score leads to almost universal recommendation for anticoagulation in those aged 65 years and over with atrial fibrillation

Background

Treatment with oral anticoagulants (OAC) for high-risk atrial fibrillation (AF) patients can reduce stroke risk by two-thirds. From 2012–14, the OAC treatment recommendation threshold in international guidelines moved from CHADS2 ≥2 to CHA2DS2-VASc ≥2 (men) or ≥3 (women), equivalent to a “sexless” CHA2DS2-VA≥2. This move aimed to identify truly low risk patients who did not need OAC treatment. General practitioners (GPs) report barriers about assessing patient suitability for OAC.

Objectives

To compare the proportion of AF patients for whom OAC treatment is recommended under CHADS2 ≥2 and CHA2DS2-VA ≥2, and to look at the drivers of any differences, using an existing dataset.

Methods

Analyses were conducted on a large Australian general practice dataset collated during previous studies (2011–2019), with deidentified data extracted from the clinical records system at a single timepoint for regularly-attending adult patients from 164 practices. CHADS2 and CHA2DS2-VA scores were calculated for AF patients with sufficient data available and the proportion with CHADS2 and CHA2DS2-VA ≥2 was compared using chi-square tests.

Results

There were records for 340,463 patients, of which 285,635 (8,294 with AF) had sufficient data to calculate CHADS2 and CHA2DS2-VA scores. Among AF patients of all ages, the CHA2DS2-VA ≥2 threshold captured a significantly higher proportion than CHADS2≥2 (85% vs 68%, p<0.0001). In AF patients aged ≥65 years, the CHA2DS2-VA ≥2 threshold also captured a significantly higher proportion than CHADS2 ≥2 (96% vs 76%, p<0.0001). Almost all older patients (≥65 years) who were captured by CHA2DS2-VA ≥2 but not CHADS2 ≥2 (n=1395) qualified on the basis of age, with only 1.4% eligible because of age 65–74 years and vascular disease history.

Conclusions

The change from CHAD2 to CHA2DS2-VA has resulted in a significantly higher proportion of patients with AF being recommended OAC treatment under the guidelines, driven almost entirely by the revised scoring for age. Among AF patients aged ≥65 years, almost all (96%) were recommended OAC treatment under CHA2DS2-VA, demonstrating that AF is strongly associated with other vascular pathology. These findings support the Canadian guidelines, which recommend OAC treatment for all AF cases aged ≥65 years. The findings also reinforce the argument that AF screening in those aged ≥65 years is justified, as almost all patients with prevalent AF in that age group are eligible for OAC treatment.

These results suggest could be an argument for simplifying the treatment message for GPs, which may reduce barriers and further improve treatment rates. High rates of associated vascular pathology in AF patients suggest that additional management strategies are also justified, including promotion of exercise, smoking cessation, and treatment of associated conditions such as hypertension and diabetes.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): RACGP Foundation / HCF Research Foundation GrantUniversity of Notre Dame Australia Research Grant

Monthly sulfadoxine/pyrimethamine-amodiaquine or dihydroartemisinin-piperaquine as malaria chemoprevention in young Kenyan children with sickle cell anemia: A randomized controlled trial

BACKGROUND

Children with sickle cell anemia (SCA) in areas of Africa with endemic malaria transmission are commonly prescribed malaria chemoprevention. Chemoprevention regimens vary between countries, and the comparative efficacy of prevention regimens is largely unknown.

METHODS AND FINDINGS

We enrolled Kenyan children aged 1 to 10 years with homozygous hemoglobin S (HbSS) in a randomized, open-label trial conducted between January 23, 2018, and December 15, 2020, in Homa Bay, Kenya. Children were assigned 1:1:1 to daily Proguanil (the standard of care), monthly sulfadoxine/pyrimethamine-amodiaquine (SP-AQ), or monthly dihydroartemisinin-piperaquine (DP) and followed monthly for 12 months. The primary outcome was the cumulative incidence of clinical malaria at 12 months, and the main secondary outcome was the cumulative incidence of painful events by self-report. Secondary outcomes included other parasitologic, hematologic, and general events. Negative binomial models were used to estimate incidence rate ratios (IRRs) per patient-year (PPY) at risk relative to Proguanil. The primary analytic population was the As-Treated population. A total of 246 children were randomized to daily Proguanil (n = 81), monthly SP-AQ (n = 83), or monthly DP (n = 82). Overall, 53.3% (n = 131) were boys and the mean age was 4.6 ± 2.5 years. The clinical malaria incidence was 0.04 episodes/PPY; relative to the daily Proguanil group, incidence rates were not significantly different in the monthly SP-AQ (IRR: 3.05, 95% confidence interval [CI]: 0.36 to 26.14; p = 0.39) and DP (IRR: 1.36, 95% CI: 0.21 to 8.85; p = 0.90) groups. Among secondary outcomes, relative to the daily Proguanil group, the incidence of painful events was not significantly different in the monthly SP-AQ and DP groups, while monthly DP was associated with a reduced rate of dactylitis (IRR: 0.47; 95% CI: 0.23 to 0.96; p = 0.038). The incidence of Plasmodium falciparum infection relative to daily Proguanil was similar in the monthly SP-AQ group (IRR 0.46; 95% CI: 0.17 to 1.20; p = 0.13) but reduced with monthly DP (IRR 0.21; 95% CI: 0.08 to 0.56; p = 0.002). Serious adverse events were common and distributed between groups, although compared to daily Proguanil (n = 2), more children died receiving monthly SP-AQ (n = 7; hazard ratio [HR] 5.44; 95% CI: 0.92 to 32.11; p = 0.064) but not DP (n = 1; HR 0.61; 95% CI 0.04 to 9.22; p = 0.89), although differences did not reach statistical significance for either SP-AQ or DP. Study limitations include the unexpectedly limited transmission of P. falciparum in the study setting, the high use of hydroxyurea, and the enhanced supportive care for trial participants, which may limit generalizability to higher-transmission settings where routine sickle cell care is more limited.

CONCLUSIONS

In this study with limited malaria transmission, malaria chemoprevention in Kenyan children with SCA with monthly SP-AQ or DP did not reduce clinical malaria, but DP was associated with reduced dactylitis and P. falciparum parasitization. Pragmatic studies of chemoprevention in higher malaria transmission settings are warranted.

TRIAL REGISTRATION

clinicaltrials.gov (NCT03178643). Pan-African Clinical Trials Registry: PACTR201707002371165.

Effect of three years' seasonal malaria chemoprevention on molecular markers of resistance of Plasmodium falciparum to sulfadoxine-pyrimethamine and amodiaquine in Ouelessebougou, Mali

Background

In 2012, seasonal malaria chemoprevention (SMC) was recommended as policy for malaria control by the World Health Organization (WHO) in areas of highly seasonal malaria transmission across the Sahel sub-region in Africa along with monitoring of drug resistance. We assessed the long-term impact of SMC on Plasmodium falciparum resistance to sulfadoxine-pyrimethamine (SP) and amodiaquine (AQ) over a 3-year period of SMC implementation in the health district of Ouelessebougou, Mali.

Methods

In 8 randomly selected sub-districts of Ouelessebougou, Mali, children aged 0–5 years were randomly selected during cross-sectional surveys at baseline (August 2014) and 1, 2 and 3 years post-SMC, at the beginning and end of the malaria transmission season. Blood smears and blood spots on filter paper were obtained and frequencies of mutation in P. falciparum genes related to resistance to SP and AQ (Pfdhfr, Pfdhps, Pfmdr1, and Pfcrt) were assessed by PCR amplification on individual samples and PCR amplification followed by deep sequencing on pooled (by site and year) samples.

Results

At each survey, approximately 50–100 individual samples were analysed by PCR amplification and a total of 1,164 samples were analysed by deep sequencing with an average read depth of 18,018–36,918 after pooling by site and year. Most molecular markers of resistance did not increase in frequency over the period of study (2014–2016). After 3 years of SMC, the frequencies of Pfdhps 540E, Pfdhps 437G and Pfcrt K76T remained similar compared to baseline (4.0 vs 1.4%, p = 0.41; 74.5 vs 64.6%, p = 0.22; 71.3 vs 67.4%, p = 0.69). Nearly all samples tested carried Pfdhfr 59R, and this proportion remained similar 3 years after SMC implementation (98.8 vs 100%, p = 1). The frequency of Pfmdr1 N86Y increased significantly over time from 5.6% at baseline to 18.6% after 3 years of SMC (p = 0.016). Results of pooled analysis using deep sequencing were consistent with those by individual analysis with standard PCR, but also indicated for the first time the presence of mutations at the Pfdhps A581G allele at a frequency of 11.7% after 2 years of SMC, as well as the Pfdhps I431V allele at frequencies of 1.6–9.3% following 1 and 2 years of SMC, respectively.

Conclusion

Two and 3 years of SMC implementation were associated with increased frequency of the Pfmdr1 N86Y mutation but not Pfdhps 540E, Pfdhps 437G and Pfcrt K76T. The first-time detection of the Pfdhps haplotype bearing the I431V and A581G mutations in Mali, even at low frequency, warrants further long-term surveillance.

Atrial fibrillation self-screening, management and guideline recommended therapy (AF SELF SMART): improving AF screening in general practice by utilising self-screening stations in GP waiting rooms

Background

Opportunistic screening for silent atrial fibrillation (AF) is recommended to reduce stroke, but screening rates are sub-optimal in Australian general practice (<15%), with practitioners reporting time constraints being the main barrier. Previous AF screening interventions in general practice have not been able to exceed screening rates of ∼34% eligible patients which is sub-optimal for stroke prevention.

Purpose

To increase the proportion of patients screened for AF in general practice by implementing AF self-screening stations in waiting rooms.

Methods

We developed and tested an AF self-screening station using a single-lead ECG and app with automated ECG analysis. We also developed customised software which fully integrates the self-screening station with GP medical software and the practice workflow (Figure 1). The system: 1) automatically identifies eligible patients (aged ≥65 years, no AF diagnosis) from the practice appointment diary, and sends an SMS regarding self-screening prior to their appointment; 2) automatically creates individualised patient QR codes, which provided to the patient by the receptionist; 3) the patient then scans QR code and self-screens at station in waiting room; 4) the ECG and result are automatically imported into patient record before the GP consultation.

Results

Three general practices in New South Wales, Australia, were recruited. Each practice participated for approximately 3-months (between August 2020 and March 2021). During this period 825 patients completed AF self-screening, mean age 74.2 years and 45% male. When expressed as a proportion of the actual eligible patients attending the practice during the study period, the mean proportion screened in practices was 52% (range 38–65%). The device algorithm indicated “Possible AF” in 37/825 patients (4.5%); mean age 77.2 years 43% male.

Conclusion

An AF self-screening station placed in GP waiting rooms that is integrated with the practice software and workflow may achieve higher screening rates for AF in general practice than standard practice, and therefore contribute to greater reductions in stroke.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Investigator-lead grant from Bristol Myers Squibb and Pfizer

Patient self-screening stations for atrial fibrillation in general practice waiting rooms: process evaluation

Background

Our previous work has identified factors relevant to general practitioner (GP)-led screening for atrial fibrillation (AF) in Australian general practices, with GPs indicating significant time constraints. AF SELF SMART (Atrial fibrillation self-screening, management and guideline recommended therapy) allows for opportunistic patient self-screening using purpose-built screening stations located in GP waiting rooms (figure 1). It utilises a single-lead ECG, with results automatically imported into the patient medical record for review during the GP consultation. AF SELF SMART may increase screening rates, but acceptability by practice staff is unknown.

Purpose

Determine staff perspectives on opportunistic self-screening in practice waiting rooms, utilising AF SELF SMART.

Method

14 semi-structured interviews have been conducted with practice staff (GPs, receptionists and practice managers) across 3 practices participating in the AF SELF SMART pilot, with thematic analysis of results.

Results

Several themes were identified.

All staff acknowledged the importance of increasing screening for AF in the practice. GPs in particular placed a high value on AF screening for stroke prevention. GPs valued the increased information and accuracy provided by AF SELF SMART, as previously they checked patients for AF using manual methods, either routinely or as clinically indicated. There were differential impacts on workflow. GPs reported some small increase in workload but these were seen as being acceptable given the benefits of the program. Receptionists and Practice Managers reported significant interruptions to normal workflow associated with assisting patients. Receptionists routinely offered patients help with screening instead of patients screening independently. Staff perceived that patients were either unable to negotiate the self-screening process by themselves, or did not want to try. Given the increase in workload associated with assisting patients, and as screening was not receptionists' main priority, not all patients were offered self-screening during busy periods. Patient refusal was also identified as a factor limiting uptake.

Conclusion

While AF self-screening may increase screening rates, further process improvements are required to reduce impact on reception staff, and enhance the usability of the self-screening station for patients. Such improvements may increase acceptability and ongoing sustainability at a practice level.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Investigator initiated research grant from Bristol-Myers Squibb/Pfizer Alliance Figure 1. Self-screening station

Atrial fibrillation screening: feasible approaches and implementation challenges across Europe

Background

Atrial fibrillation (AF) screening has the potential to increase early detection and possibly reduce complications of AF. Guidelines recommend screening, but the most appropriate approaches are unknown.

Purpose

We aimed to explore the views of stakeholders across Europe about the opportunities and challenges of implementing four different AF screening scenarios.

Method

This qualitative study included 21 semi-structured interviews with healthcare professionals and regulators potentially involved in AF screening implementation in nine European countries. Data were analysed using thematic analysis.

Results

Three themes evolved. 1) Current approaches to screening: there are no national AF screening programmes, with most AF detected in symptomatic patients. Patient-led screening exists via personal devices, creating screening inequity by the reach of screening programmes being limited to those who access healthcare services. 2) Feasibility of screening approaches: single time point opportunistic screening in primary care using single lead ECG devices was considered the most feasible approach and AF screening may be possible in previously unexplored settings such as dentists and podiatrists. Software algorithms may aid identification of patients suitable for screening and telehealth services have the potential to support diagnosis. However, there is a need for advocacy to encourage the use of telehealth to aid AF diagnosis, and training for screening familiarisation and troubleshooting.

3) Implementation requirements: sufficient evidence of benefit is required. National rather than pan-European screening processes must be developed due to different payment mechanisms and health service regulations.

There is concern that the rapid spread of wearable devices for heart rate monitoring may increase workload due to false positives in low risk populations for AF. Data security and inclusivity for those without access to primary care or personal devices must be addressed.

Conclusions

There is an overall awareness of AF screening. Opportunistic screening appears to be most feasible across Europe. Challenges that need to be addressed concern health inequalities, identification of best target groups for screening, streamlined processes, the need for evidence of benefit, and a tailored approach adapted to national realities.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): H2020 Screening ScenariosGraphical abstract

One size does not fit all – a realist review of screening for asymptomatic atrial fibrillation in Indigenous communities in Australia, Canada, New Zealand and United States

Background/Introduction

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and it is increasing in prevalence and incidence globally. True prevalence is underestimated because silent/asymptomatic AF is frequent and under-detected, but can cause stroke. Guidelines recommend opportunistic screening for AF in patients aged ≥65 years old. A growing body of evidence from hospital and community-based studies in Australia, New Zealand, Canada and United States indicates this age limit is lower for Indigenous people. Screening for AF meets the World Health Organisation (WHO) criteria for successful routine screening, yet little is known about successful implementation of AF screening in Indigenous communities in developed countries.

Purpose

The aim of this study is to use a realist approach to identify what works, how, for whom and under what circumstances for AF screening of Indigenous communities in Australia, Canada, New Zealand and United States.

Methods

In the realist review, eight databases were searched for studies targeted at AF screening in Indigenous communities. Realist analysis was used to identify context-mechanism-outcome configurations across 11 included records (reporting on 5 studies). Snowball referencing and grey literature were used to iteratively incorporate evidence to enhance the refined programme theory that was the product of the realist analysis.

Results

The realist review included studies using multiple screening strategies such as using tools to increase screening, using different screening environments and training screeners to provide culturally centred care. The realist analysis identified a number of mechanisms that can improve AF screening in Indigenous communities. The contextual factors enabling AF screening programs in Indigenous communities include wider community engagement, opportunistic non-clinical settings, using portable and easy to use devices, increasing knowledge, motivation and confidence in screening amongst Indigenous healthcare workers as well as improving follow-up protocols for abnormal results tailored to screen setting. Barriers to effective AF screening include time-poor working environments, conflicting cultural issues, navigating communication of abnormal results and logistical issues with device use (Figure 1).

Conclusion(s)

Since the life-course risk for AF in Indigenous population is different, a modified screening strategy needs to be put in place. This realist review provides lessons learned for successful implementation of AF screening programs for Indigenous communities. In order to tackle the gap in cardiovascular burden in Indigenous people, this study calls for action to develop AF screening guidelines for Indigenous populations and provides a guide for policy makers about timely and effective AF screening programs for Indigenous communities.

Funding Acknowledgement

Type of funding sources: None.

Epidemiology of Plasmodium falciparum Infections in a Semi-Arid Rural African Setting: Evidence from Reactive Case Detection in Northwestern Kenya

In northwestern Kenya, Turkana County has been historically considered unsuitable for stable malaria transmission because of its unfavorable climate and predominantly semi-nomadic population; consequently, it is overlooked during malaria control planning. However, the area is changing, with substantial development, an upsurge in travel associated with resource extraction, and more populated settlements forming. Recently, numerous malaria outbreaks have highlighted the need to characterize malaria transmission and its associated risk factors in the region to inform control strategies. Reactive case detection of confirmed malaria cases at six health facilities across central Turkana was conducted from 2018 to 2019. Infections in household members of index cases were detected by malaria rapid diagnostic tests (RDTs) and PCR tests, and they were grouped according household and individual characteristics. The relationships between putative risk factors and infection were quantified by multilevel logistic regression models. Of the 3,189 household members analyzed, 33.6% had positive RDT results and/or PCR test results. RDT-detected infections were more prevalent in children; however, PCR-detected infections were similarly prevalent across age groups. Recent travel was rarely reported and not significantly associated with infection. Bed net coverage was low and net crowding was associated with increased risks of household infections. Infections were present year-round, and fluctuations in prevalence were not associated with rainfall. These findings indicate year-round, endemic transmission with moderate population immunity. This is in stark contrast to recent estimates in this area. Therefore, further investigations to design effective intervention approaches to address malaria in this rapidly changing region and other similar settings across the Horn of Africa are warranted.

Performance of automated single-lead ECG atrial fibrillation screening is associated with patient characteristics

Funding Acknowledgements

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): The investigators received and unrestricted research grant by Pfizer/BMS. Pfizer/BMS was not involved in the planning, conduction, analysis, or interpretation of the data.

Introduction

Screening for atrial fibrillation (AF) with a single-lead electrocardiogram device is on the rise. However, little is known about influence of automated AF screening performance related to patient characteristics.

Aim

We tested the accuracy of automated AF detection of a single-lead ECG device and identified factors associated with diagnostic performance.

Methods

In 6482 subjects of community-pharmacies a single-time point AF screening was performed. All ECGs were analyzed by blinded human overread and compared to the automated results in context of patient characteristics.

Results

Automated screening showed good prediction of AF with an area under the receiver operating curve of 0.89; sensitivity 80%; specificity 98%; positive predictive value 71%; negative predictive value 99%. Good ECG signal quality was highly associated with correct measurement, while low signal quality leads to incorrect measurements. In a multivariate model we determined factors associated with excellent signal quality and as counterexample incorrect automatic AF identification. The Odds’ ratio (OR) for excellent signal quality was strongly associated with female sex, lower age, lower height, and higher body weight index (table).

Conclusion

The performance of automated AF screening is influenced by sex, age, height and body mass index. Potential target population groups, with high AF prevalence, have a higher chance of incorrect automatic measurement. We recommend an expert over-read, at least for all AF positive ECG recordings. Table 1 Excellent signal quality Incorrect measurement Univariate analysis Multivariate analysis Univariate analysis Multivariate analysis Parameter OR 95% CI P OR 95% CI P OR 95% CI P OR 95% CI P Sex [Female] 2.33 1.97-2.75 <0.001 1.92 1.53-2.41 <0.001 0.64 0.49-0.84 0.001 0.57 0.43-0.76 <0.001 Age [years] 0.97 0.96-0.98 <0.001 0.97 0.96-0.98 <0.001 1.07 1.04-1.09 <0.001 1.06 1.04-1.09 <0.001 Height [cm] 0.96 0.95-0.97 <0.001 0.98 0.97-0.99 0.003 1.01 0.99-1.03 0.068 Weight [kg] 0.99 0.99-1.00 0.418 0.99 0.98-0.99 0.003 BMI [kg/cm2] 1.04 1.03-1.06 <0.001 1.04 1.03-1.06 <0.001 0.91 0.88-0.95 <0.001 0.91 0.87-0.94 <0.001 CHADSVASC 1 0.95-1.06 0.912 1.06 0.97-1.17 0.205 Heart failure 0.62 0.41-0.93 0.022 1.86 1.13-3.05 0.015 Hypertension 0.96 0.83-1.11 0.58 1.06 0.80-1.39 0.689 Diabetes mellitus 0.85 0.68-1.07 0.159 0.82 0.54-1.25 0.359 Stroke / TIA 0.82 0.66-1.01 0.066 1.19 0.83-1.69 0.341 Vascular disease 0.89 0.75-1.07 0.213 1.31 0.98-1.77 0.70 OR – odd’s ratio, CI – confidence interval

Interactions Between Antenatal Sulfadoxine-Pyrimethamine, Drug-Resistant Plasmodium falciparum Parasites, and Delivery Outcomes in Malawi

BACKGROUND

Sulfadoxine-pyrimethamine (SP) is used as intermittent preventive therapy in pregnancy (IPTp) for malaria in sub-Saharan Africa. The resistance marker dhps A581G has been associated with reduced IPTp-SP efficacy and enhanced morbidity in SP recipients.

METHODS

We measured SP-resistance allele frequencies in Malawian women participating in a trial comparing IPTp with SP against intermittent screening by rapid diagnostic tests (ISTp). We genotyped polymerase chain reaction-detected parasites using deep sequencing of SP-resistance alleles.

RESULTS

Among 125 placental infections, A581G-bearing parasites were associated with reduced birth weight (mean difference [MD], 252 g; 95% confidence interval [CI], 46-457; P = .017). Relative to ISTp, IPTp-SP was associated with higher birth weights in women with wild-type parasites (MD, 116 g; 95% CI, -40 to 272; P = .142) and lower birth weights in women with A581G-bearing parasites (MD, 192 g; 95% CI, -264 to 648; P = .385) (Pinteraction = .033). Similar associations were noted on gestational age (Pinteraction = .075). Amongst only IPTp-SP recipients, relative to women who last received SP > 4 weeks before delivery, recent SP receipt was associated with lower birth weight in women with wild-type parasites (MD, 118 g; 95% CI, -376 to 139; P = .361) and higher birth weight in women with A581G-bearing parasites (MD, 783 g; 95% CI, -20 to 1586; P = .054) (Pinteraction = .005).

CONCLUSIONS

The effectiveness in birth weight of IPTp-SP is compromised by A581G-bearing parasites, but there was no evidence that the adverse effects of these parasites are exacerbated by antenatal SP.

ISRCTN REGISTRY

www.isrctn.com/ISRCTN69800930.

Mosquito Exposure and Malaria Morbidity: A Microlevel Analysis of Household Mosquito Populations and Malaria in a Population-Based Longitudinal Cohort in Western Kenya

BACKGROUND

Malaria morbidity is highly overdispersed in the population. Fine-scale differences in mosquito exposure may partially explain this heterogeneity in individual malaria outcomes.

METHODS

In 38 households we explored the effect of household-level mosquito exposure and individual insecticide-treated net (ITN) use on relative risk (RR) of confirmed malaria. We conducted monthly active surveillance (n = 254; 2624 person-months) and weekly mosquito collection (2092 household-days of collection), and used molecular techniques to confirm human blood feeding and exposure to infectious mosquitoes.

RESULTS

Of 1494 female Anopheles (89.8% Anopheles gambiae sensu lato), 88.3% were fed, 51.9% had a human blood meal, and 9.2% were sporozoite infected. In total, 168 laboratory-confirmed malaria episodes were reported (incidence rate 0.064 episodes per person-month at risk; 95% confidence interval [CI], .055-.074). Malaria risk was directly associated with exposure to sporozoite-infected mosquitoes (RR, 1.24; 95% CI, 1.11-1.38). No direct effect was measured between ITN use and malaria morbidity; however, ITN use did moderate the effect of mosquito exposure on morbidity.

CONCLUSIONS

Malaria risk increases linearly with vector density and feeding success for persons with low ITN use. In contrast, malaria risk among high ITN users is consistently low and insensitive to variation in mosquito exposure.

Comparable risk of ischemic stroke in patients with screen-detected atrial fibrillation on single timepoint handheld ECG screening to patients with known AF

Aims

To determine risk of ischemic stroke in patients with single timepoint screen-detected atrial fibrillation (AF).

Methods

Cohort of 11,972 consecutive patients aged ≥65 years attending medical outpatient clinics in Hong Kong underwent AF screening using a handheld single-lead ECG (AliveCor) from Dec 2014 to Dec 2017 (NCT02409654). Repeated screening was performed in patients who had >1 clinic visit during the study period. Cohort was divided into 4 exposure groups: (i) new AF detected by initial screening (S1-AF); (ii) new AF detected by subsequent screening or clinically diagnosed during follow up (FU-AF); (iii) known AF and (iv) no initial or subsequent FU-AF (no AF). Exposure in the FU-AF group was handled as a time-dependent variable. All AF exposure groups were further stratified by oral anticoagulant (OAC) use at the end of FU. Cumulative incidence of ischemic stroke was compared between groups during a median FU period of 2.3 (IQR=1.7–3.3) years, using Fine and Gray regression accounting for death as competing risk and using no AF as reference.

Results

Of 11,972 subjects enrolled, 2,236 (18.7%) had known AF and 9,736 (81.3%) underwent 13,571 screening events during the study period. The yield of newly diagnosed AF on initial screening was 2.3% (n=223/9,736), with 71 new AF detected by subsequent screening. During FU, 2.3% (221/9,442) screen-negative patients were diagnosed with AF clinically. Compared to no AF, S1-AF without OAC had the highest ischemic stroke risk (subdistribution hazard ratio (SHR)=2.79; 1.47–5.27), then FU-AF without OAC (SHR=2.66; 1.21–5.82) and known AF without OAC (SHR=1.97; 1.50–2.57). All AF groups taking OAC had similar risk of ischemic stroke as no AF.

Conclusion

This is the first study to report the prognosis of AF detected by single timepoint screening. The prognosis is not benign. Both risks of stroke and benefits from anticoagulation therapy were similar between screen-detected and known AF.

Funding Acknowledgement

Type of funding source: None

223Atrial fibrillation screen, management and guideline recommended therapy (AF SMART II) in the rural primary care setting: eHealth tools to support all stages of screening

Funding Acknowledgements

National Heart Foundation of Australia: CVRN Grant and Vanguard Grant; investigator-initiated grant from Pfizer-BMS; AliveCor provided free devices

BACKGROUND

Internationally, most atrial fibrillation (AF) management guidelines recommend screening for AF in people aged ≥65 years, as well as treatment with oral anticoagulants (OAC) for those at high stroke risk ( CHA2DS2-VA ≥2). However, in practice, gaps remain in both screening and treatment. In Australian general practice in 2017, the estimated rate of AF screening was 11%, and only about 60% of diagnosed AF patients received guideline-based OAC. Our 2018 screening study using eHealth tools in metropolitan general practices increased screening to 16% of eligible patients, leading to further refinement of the eHealth tools.

PURPOSE

To investigate the impact of an AF screening program in rural general practices, using a suite of custom-designed eHealth tools designed to increase the proportion screened and treated for AF in accordance with guidelines.

METHODS

General practices (n = 8) in rural New South Wales, Australia participated in the study between September 2018 – June 2019. General practitioners (GPs) and practice nurses conducted opportunistic screening of eligible patients (i.e. aged ≥65 years without existing AF diagnosis) using a smartphone electrocardiogram during practice visits. Practices were also provided with 1) an electronic screening prompt (which appeared when an eligible patient’s file was opened); 2) electronic decision support based on ESC/Australian treatment guidelines; and 3) regular customised data reports aimed at quality improvement (Figure 1). A clinical audit tool was used to extract deidentified data from practices.

RESULTS

A total of 3,103 eligible patients (mean age 75.1 ± 6.8 years, 47% male) who attended the 8 practices during the study period were screened (median screening period 4.6 months). Practices screened a median of 35% of eligible patients (range 9-51% per practice), with 4/8 practices screening >40% of eligible patients. 36 (1.2%) new cases of AF were confirmed (mean age 77.0 years, 64% male, mean CHA2DS2-VA = 2.9). GPs (n = 22) screened 30% (range 1-182 per GP) of patients and nurses (n = 40) screened 70% (range 1-192 per nurse). OAC treatment rates of patients with AF with CHA2DS2-VA≥2 were 82% (screen-detected), 78% (clinically-detected during study period) and 75% (pre-existing AF), with no significant differences between groups.

CONCLUSIONS

In the rural general practice setting, an AF screening program supported by eHealth tools resulted in 35% of eligible people screened, which is substantially higher than the 16% achieved in our previous study. Half the practices screened 40-50% of eligible patients, suggesting this may represent a ‘ceiling’ of patients captured by opportunistic AF screening programs. OAC treatment rates were higher than previous studies at baseline and were trending upwards during the study. eHealth tools, particularly including customised data reports as part of an audit and feedback system, may be a valuable addition to future screening programs.

Abstract Figure 1 - screening process

Direct Estimation of Sensitivity of Plasmodium falciparum Rapid Diagnostic Test for Active Case Detection in a High-Transmission Community Setting

Community-based active case detection of malaria parasites with conventional rapid diagnostic tests (cRDTs) is a strategy used most commonly in low-transmission settings. We estimated the sensitivity of this approach in a high-transmission setting in Western Kenya. We tested 3,547 members of 912 households identified in 2013-2014 by index children with (case) and without (control) cRDT-positive malaria. All were tested for Plasmodium falciparum with both a cRDT targeting histidine-rich protein 2 and with an ultrasensitive real-time polymerase chain reaction (PCR). We computed cRDT sensitivity against PCR as the referent, compared prevalence between participant types, and estimated cRDT detectability as a function of PCR-estimated parasite density. Parasite prevalence was 22.9% by cRDTs and 61.5% by PCR. Compared with children aged < 5 years or adults aged > 15 years, geometric mean parasite densities (95% CI) were highest in school-age children aged 5-15 years (8.4 p/uL; 6.6-10.6). The overall sensitivity of cRDT was 36%; among asymptomatic household members, cRDT sensitivity was 25.5% and lowest in adults aged > 15 years (15.8%). When modeled as a function of parasite density, relative to school-age children, the probability of cRDT positivity was reduced in both children aged < 5 years (odds ratio [OR] 0.48; 95% CI: 0.34-0.69) and in adults aged > 15 years (OR: 0.35; 95% CI: 0.27-0.47). An HRP2-detecting cRDT had poor sensitivity for active P. falciparum case detection in asymptomatic community members, and sensitivity was lowest in highly prevalent low-density infections and in adults. Future studies can model the incremental effects of high-sensitivity rapid diagnostic tests and the impacts on transmission.

Association between beta-blocker use and obesity in Hong Kong Chinese elders: a post-hoc analysis

INTRODUCTION

Studies of Caucasian populations have shown that beta-blockers may exacerbate weight gain, a risk factor for many chronic diseases. Still, beta-blockers are the most prescribed antihypertensives in the Chinese population in Hong Kong. We aimed to explore the association between beta-blocker use, hypertension, and weight status of this population.

METHODS

A post-hoc analysis regarding body mass index (BMI) and the use of beta-blockers was performed based on the medication profile of community-dwelling older adults. Participants' BMI, hypertension diagnosis, name, dose, frequency, route of administration of beta-blockers, and other drugs that may alter body weight were recorded.

RESULTS

Of 1053 Chinese individuals aged ≥65 years (mean age 76.9±7.2 years, 80% female) from 32 elderly centres in Hong Kong, 18% (185/1053) of them consumed beta-blockers. That group also had a significantly larger proportion of obese individuals (45.9% vs 32.1%, P=0.002). After adjusting for other weight-altering drugs, beta-blockers remained a significant predictor of overweight and obesity (P=0.001). As the hypertensive population had significantly higher BMI than the normotensive population (24.3±3.6 vs 22.9±3.5, P<0.001), a sub-analysis on those with hypertension diagnosis confirmed that only the hypertensive population taking atenolol had a significantly larger population of obese individuals (BMI ≥25) compared with those who took metoprolol (58.9% vs 38.5%, P=0.03) and those who did not take any beta-blockers (58.9% vs 38.4%, P=0.007).

CONCLUSIONS

Our findings taken together with other guideline reservations cast doubt on whether beta-blockers, particularly atenolol, should be the major drug prescribed to older adults with hypertension.

845. Children with Clinical Plasmodium falciparum Infection Have Increased Sharing of Haplotypes with Household Members as well as Temporally Proximal, Symptomatic Peers

Background

Methods

Results

Conclusion

Disclosures

P3760Temporal trends in stroke prevalence and its associations with changing patterns of antithrombotic regimens in patients with atrial fibrillation and a wide spectrum of coronary artery disease

Introduction

Much of the morbidity and mortality associated with atrial fibrillation (AF) is due to cerebrovascular thrombo-embolic complications such as ischemic stroke. Antithrombotic therapy is the fundamental treatment for many cardiovascular conditions, e.g. coronary artery disease (CAD), AF, and stroke to prevent thrombotic complications and death, but many patients have both CAD and AF. Dual antiplatelet therapy (DAPT) with acetylsalicylic acid (ASA) and a P2Y12 inhibitor has proven most effective in patients with recent myocardial infarction (MI) or after percutaneous coronary intervention (PCI), whereas for AF, oral anticoagulation (OAC) is most effective, with lesser efficacy but similar bleeding using DAPT. We investigated temporal trends in stroke prevalence and its associations with changing patterns of antithrombotic regimens in patients with non-valvular AF and a wide spectrum of co-incident CAD.

Methods

The Silesian TRiplE Antithrombotic Therapy (TREAT) Registry enrolled 14,873 patients with CAD from 2006 to 2014: 9,379 with stable CAD (SCAD), 1,460 with unstable angina (UA), 1,760 with NSTEMI and 2,328 with STEMI. We compared temporal trends in clinical features, an incidence of clinical events and patterns of antithrombotic regimens.

Results

2,194 of 14,873 patients (14.6%) had AF, including 74.1% with SCAD, 7.7% with UA, 10.1% with NSTEMI and 8.1% with STEMI. The AF prevalence increased from 11.2% in 2006 to 17.2% in 2014 which may be attributed to increasing age from 62.7 in 2006 to 67.8 in 2014. Overall, there was an increasing use of OAC therapy alone or with SAPT or DAPT from 46–50% in 2006–7 to 77–86%% in 2013–14. There was a steady increase in utilization of TREAT, and OAC ± SAPT throughout the study period (Panel A): after PCI there was a substantial increase in TREAT with a steady decline in DAPT (Panel B). The stroke rates declined throughout the study period from 3.3% in 2004 through a peak of 4.9% in 2011 to 1.1% in 2014. Conversely, bleeding rates increased from 6.0% to 10.5%.

Conclusions

There has been an increase followed by a progressive decline in stroke rate despite increasing age and AF prevalence in patients with both CAD and AF. This phenomenon is associated with a significant increase in the proportion of AF patients receiving guideline-recommended OAC therapy, driven by a steady increase in the utilization of triple antithrombotic therapy in patients following ACS or stent implantation and increase in OAC monotherapy in patients without ACS or stent implantation. This positive effect on stroke incidence is offset by increased bleeding risk, necessitating a closer look at the duration of triple therapy for ACS or PCI, and the long-term requirement for additional antiplatelet treatment in uncomplicated CAD.

P3769Rapid referral to a one-stop AF clinic following possible AF detection by community pharmacists leads to early diagnosis and appropriate anticoagulant treatment

Background

Atrial fibrillation is the most common cardiac arrhythmia globally, responsible for one third of ischaemic strokes, often resulting in death or incapacity. This condition, frequently asymptomatic is estimated to be up to 50% undiagnosed. Reducing this risk with appropriate detection and management strategies offers substantial economic and patient benefits. Community pharmacists have been shown to be an accessible healthcare professional capable of detecting atrial fibrillation. Concerns raised utilising community pharmacists is the additional workload for primary care physicians, and lack of a clear pathway to ensure patients are adequate followed with assurance of initiation of anticoagulation therapy.

Purpose

To assess the feasibility of screening by community pharmacists with onward referral to an innovative one-stop AF clinic to enable identification of new cases of AF and subsequent initiation of anticoagulation within 2 weeks.

Methods

21 pharmacies were recruited and trained on pathophysiology of AF and demonstration of pulse taking using pulse check and Kardia mobile device. Any person walking into a community pharmacy aged ≥65 years was offered a free pulse check. For any irregularity detected, individualised counselling was offered with a referral made to a one-stop AF clinic for confirmation and initiation of anticoagulation. Written patient consent was obtained.

Results

672 people were recruited with an average age of 69±3.5 years and 58% female (n=389). There was a history of hypertension in 618 (92%) and diabetes in 242 (36%), the most common co-morbidities. 45 people were referred following an irregular pulse or abnormal ECG rhythm strip, of whom 11 (1.6% of total population) had a confirmed AF diagnosis within 30 day follow up. An additional 8 cases with known AF not receiving anticoagulation termed (actionable AF) were also referred. All 19 cases of new or untreated AF were prescribed anticoagulation by the one stop clinic in accordance with guideline recommendations

Conclusions

ESC guidance recommends opportunistic screening for AF by pulse taking or ECG rhythm strip in patients ≥65 years of age. The 1.6% incidence of new AF was in accordance with meta-analyses identifying 1.4% of those aged ≥65 on a single time point check for presence of AF. Our model utilises the un-tapped skills of community pharmacy to deliver pulse checks of ECG rhythm recordings in an accessible primary care location with a clear referral pathway that is effective in early review and ensuring suitable patients receive anticoagulation. The innovative pathway could provide remote triage at scale and help address the missing people with undiagnosed and actionable AF by opening new channels for identification by healthcare professionals managing long term conditions who like pharmacists have not been considered suitable healthcare professionals due to lack of an established pathway for confirming the potential diagnosis of AF.

Acknowledgement/Funding

NHS England Test Bed Programme

P6537Screening for Atrial Fibrillation in Native Americans using iPhone ECG

Background

Atrial fibrillation (AF) is a major risk factor for stroke. Screening for silent AF, with subsequent initiation of anticoagulation in at-risk individuals, may decrease the risk of stroke. Native Americans (NA) have a high prevalence of diabetes and higher incidence of stroke than whites and blacks. Indigenous Australians, and Maori in New Zealand develop AF on average 10–20 years earlier than Europeans and Asians living in the same country. We hypothesized that screening for AF using a single time point, 30-second iPhone-based ECG recording will result in identification of silent AF in a significant number of NA compared to routine care, and that the age profile of those detected may be younger than non-NA.

Purpose

To determine the prevalence of AF, and incidence of unknown AF in NA seen at a tribal clinic using opportunistic screening with a single-lead iPhone-based ECG device (Kardia Mobile).

Methods

A database study was carried out in NA patients aged ≥50 followed to determine the prevalence of AF. Consecutive patients aged ≥50 with no prior history of AF were approached when attending the AST clinic for a primary care visit for opportunistic screening. Following consent, a 30-second ECG was recorded. A cardiologist overread all tracings to confirm the diagnosis of AF. Those confirmed to have AF were referred to a cardiologist for further management.

Results

The AF prevalence in 2952 NA patients aged ≥50 (1256 male, 1696 female), was 2.2%. Prevalence increased significantly with age (age 50–59, 0.9%; age 60–69, 2.6%; age 70–79, 3.6%; age ≥80, 7.8%; p for trend <0.0001). There were significant sex differences in AF prevalence (males 3.6% vs. females 1.2% p<0.0001). The mean age of those with AF was significantly older than for those without AF (69±10 vs, 63±6 respectively, p<0.0001). In the first month following study commencement in Jan 2019, 157 eligible patients without AF were approached and 142 (90%) agreed to receive screening for AF. The mean age of those enrolled was 62±8 years (66% women), and mean CHA2DS2-VASc score was 2.3±1.4.The age and sex distribution of those screened was similar to the overall clinic population without AF. Two of 142 patients (1.4%; age 59 and 61, respectively) screened were diagnosed with AF and were referred to a cardiologist. Enrollment is planned to reach 1500 patients by August 2019.

Conclusions

Opportunistic screening for AF using iPhone ECG in NA is feasible and well accepted by the patients when attending a tribal clinic. Our preliminary data suggest that NA, like other first nation peoples, may develop AF at a younger age compared to non-NA populations and would be likely to benefit from AF screening. In light of the high prevalence of risk factors for development of AF in NA, this novel approach for AF screening in tribal clinics has the potential to improve health outcomes among a large number of individuals.

Continual near-infrared spectroscopy monitoring in the injured lower limb and acute compartment syndrome: an FDA-IDE trial

Aims

The aim of this study was to evaluate near-infrared spectroscopy (NIRS) as a continuous, non-invasive monitor for acute compartment syndrome (ACS).

Patients and Methods

NIRS sensors were placed on 86 patients with, and 23 without (controls), severe leg injury. NIRS values were recorded for up to 48 hours. Longitudinal data were analyzed using summary and graphical methods, bivariate comparisons, and multivariable multilevel modelling.

Results

Mean NIRS values in the anterior, lateral, superficial posterior, and deep posterior compartments were between 72% and 78% in injured legs, between 69% and 72% in uninjured legs, and between 71% and 73% in bilaterally uninjured legs. In patients without ACS, the values were typically > 3% higher in injured compartments. All seven limbs with ACS had at least one compartment where NIRS values were 3% or more below a reference uninjured control compartment. Missing data were encountered in many instances.

Conclusion

NIRS oximetry might be used to aid the assessment and management of patients with ACS. Sustained hyperaemia is consistent with the absence of ACS in injured legs. Loss of the hyperaemic differential warrants heightened surveillance. NIRS values in at least one injured compartment(s) were > 3% below the uninjured contralateral compartment(s) in all seven patients with ACS. Additional interventional studies are required to validate the use of NIRS for ACS monitoring. Cite this article: Bone Joint J 2018;100-B:787-97.

Pleiotropic, heart rate-independent cardioprotection by ivabradine

BACKGROUND AND PURPOSE

In pigs, ivabradine reduces infarct size even when given only at reperfusion and in the absence of heart rate reduction. The mechanism of this non-heart rate-related cardioprotection is unknown. Hence, in the present study we assessed the pleiotropic action of ivabradine in more detail.

EXPERIMENTAL APPROACH

Anaesthetized mice were pretreated with ivabradine (1.7 mg · kg(-1) i.v.) or placebo (control) before a cycle of coronary occlusion/reperfusion (30/120 min ± left atrial pacing). Infarct size was determined. Isolated ventricular cardiomyocytes were exposed to simulated ischaemia/reperfusion (60/5 min) in the absence and presence of ivabradine, viability was then quantified and intra- and extracellular reactive oxygen species (ROS) formation was detected. Mitochondria were isolated from mouse hearts and exposed to simulated ischaemia/reperfusion (6/3 min) in glutamate/malate- and ADP-containing buffer in the absence and presence of ivabradine respectively. Mitochondrial respiration, extramitochondrial ROS, mitochondrial ATP production and calcium retention capacity (CRC) were assessed.

KEY RESULTS

Ivabradine decreased infarct size even with atrial pacing. Cardiomyocyte viability after simulated ischaemia/reperfusion was better preserved with ivabradine, the accumulation of intra- and extracellular ROS decreased in parallel. Mitochondrial complex I respiration was not different without/with ivabradine, but ivabradine significantly inhibited the accumulation of extramitochondrial ROS, increased mitochondrial ATP production and increased CRC.

CONCLUSION AND IMPLICATIONS

Ivabradine reduces infarct size independently of a reduction in heart rate and improves ventricular cardiomyocyte viability, possibly by reducing mitochondrial ROS formation, increasing ATP production and CRC.

Methodological considerations when assessing restricted and repetitive behaviors and aggression

Methodological issues impacting the relationship between aggression and restricted, repetitive, and stereotyped behaviors and interests (RRSBI) were examined in 2648 children and adolescents with autism spectrum disorders (ASD) using a multi-method, multi-informant analysis model to assess the effects of informant, assessment method, and aggression phenotype. Overall, a significant, but small relationship was found between RRSBI and aggression (p < .05). There was significant heterogeneity of estimates with large effect sizes observed when utilizing teacher report and a broad phenotype of aggression. Variance in estimates was attributed to differences in informant and assessment method with two times greater effect attributed to informant. Results suggest strategies to optimize future investigations of the relationship between RRSBI and aggression. Findings also provide the opportunity for the development of targeted interventions for aggression in youth with ASD.

Changes in sexual behaviour between 1986 and 1988 in matched samples of homosexually active men

Matched samples of homosexually active men were obtained using identical sampling methods in a city of one million people in 1986 and 1988. Data indicated that reported sexual behaviours had significantly changed in the direction of safer sex, particularly oral sex without ejaculation, anal sex with a condom (both insertive and receptive), which increased in frequency, and analingual and digitoanal receptive practices, wet kissing, and anal receptive intercourse generally, which decreased. Reported sources of education for both samples were primarily gay media and gay organisations. These data, with some caveats concerning design and comparability of samples, suggest that behavioural change in the appropriate direction has occurred in homosexually active men, and that gay organisations and media have been perceived as the most common source of information on safer sex in this population.