Paths and timings of the peopling of Polynesia inferred from genomic networks.

Polynesia was settled in a series of extraordinary voyages across an ocean spanning one third of the Earth1, but the sequences of islands settled remain unknown and their timings disputed. Currently, several centuries separate the dates suggested by different archaeological surveys2-4. Here, using genome-wide data from merely 430 modern individuals from 21 key Pacific island populations and novel ancestry-specific computational analyses, we unravel the detailed genetic history of this vast, dispersed island network. Our reconstruction of the branching Polynesian migration sequence reveals a serial founder expansion, characterized by directional loss of variants, that originated in Samoa and spread first through the Cook Islands (Rarotonga), then to the Society (Totaiete ma) Islands (11th century), the western Austral (Tuha'a Pae) Islands and Tuamotu Archipelago (12th century), and finally to the widely separated, but genetically connected, megalithic statue-building cultures of the Marquesas (Te Henua 'Enana) Islands in the north, Raivavae in the south, and Easter Island (Rapa Nui), the easternmost of the Polynesian islands, settled in approximately AD 1200 via Mangareva.

Variation in ERAP2 has opposing effects on severe respiratory infection and autoimmune disease.

ERAP2 is an aminopeptidase involved in immunological antigen presentation. Genotype data in human samples from before and after the Black Death, an epidemic due to Yersinia pestis, have marked changes in allele frequency of the single-nucleotide polymorphism (SNP) rs2549794, with the T allele suggested to be deleterious during this period, while ERAP2 is also implicated in autoimmune diseases. This study explored the association between variation at ERAP2 and (1) infection, (2) autoimmune disease, and (3) parental longevity. Genome-wide association studies (GWASs) of these outcomes were identified in contemporary cohorts (UK Biobank, FinnGen, and GenOMICC). Effect estimates were extracted for rs2549794 and rs2248374, a haplotype tagging SNP. Additionally, cis expression and protein quantitative trait loci (QTLs) for ERAP2 were used in Mendelian randomization (MR) analyses. Consistent with decreased survival in the Black Death, the T allele of rs2549794 showed evidence of association with respiratory infection (odds ratio; OR for pneumonia 1.03; 95% CI 1.01-1.05). Effect estimates were larger for more severe phenotypes (OR for critical care admission with pneumonia 1.08; 95% CI 1.02-1.14). In contrast, opposing effects were identified for Crohn disease (OR 0.86; 95% CI 0.82-0.90). This allele was shown to associate with decreased ERAP2 expression and protein levels, independent of haplotype. MR analyses suggest that ERAP2 expression may be mediating disease associations. Decreased ERAP2 expression is associated with severe respiratory infection with an opposing association with autoimmune diseases. These data support the hypothesis of balancing selection at this locus driven by autoimmune and infectious disease.

Native American gene flow into Polynesia predating Easter Island settlement.

The possibility of voyaging contact between prehistoric Polynesian and Native American populations has long intrigued researchers. Proponents have pointed to the existence of New World crops, such as the sweet potato and bottle gourd, in the Polynesian archaeological record, but nowhere else outside the pre-Columbian Americas1-6, while critics have argued that these botanical dispersals need not have been human mediated7. The Norwegian explorer Thor Heyerdahl controversially suggested that prehistoric South American populations had an important role in the settlement of east Polynesia and particularly of Easter Island (Rapa Nui)2. Several limited molecular genetic studies have reached opposing conclusions, and the possibility continues to be as hotly contested today as it was when first suggested8-12. Here we analyse genome-wide variation in individuals from islands across Polynesia for signs of Native American admixture, analysing 807 individuals from 17 island populations and 15 Pacific coast Native American groups. We find conclusive evidence for prehistoric contact of Polynesian individuals with Native American individuals (around AD 1200) contemporaneous with the settlement of remote Oceania13-15. Our analyses suggest strongly that a single contact event occurred in eastern Polynesia, before the settlement of Rapa Nui, between Polynesian individuals and a Native American group most closely related to the indigenous inhabitants of present-day Colombia.

Genome-wide association study of leprosy in Malawi and Mali.

Leprosy is a chronic infection of the skin and peripheral nerves caused by Mycobacterium leprae. Despite recent improvements in disease control, leprosy remains an important cause of infectious disability globally. Large-scale genetic association studies in Chinese, Vietnamese and Indian populations have identified over 30 susceptibility loci for leprosy. There is a significant burden of leprosy in Africa, however it is uncertain whether the findings of published genetic association studies are generalizable to African populations. To address this, we conducted a genome-wide association study (GWAS) of leprosy in Malawian (327 cases, 436 controls) and Malian (247 cases, 368 controls) individuals. In that analysis, we replicated four risk loci previously reported in China, Vietnam and India; MHC Class I and II, LACC1 and SLC29A3. We further identified a novel leprosy susceptibility locus at 10q24 (rs2015583; combined p = 8.81 × 10-9; OR = 0.51 [95% CI 0.40 - 0.64]). Using publicly-available data we characterise regulatory activity at this locus, identifying ACTR1A as a candidate mediator of leprosy risk. This locus shows evidence of recent positive selection and demonstrates pleiotropy with established risk loci for inflammatory bowel disease and childhood-onset asthma. A shared genetic architecture for leprosy and inflammatory bowel disease has been previously described. We expand on this, strengthening the hypothesis that selection pressure driven by leprosy has shaped the evolution of autoimmune and atopic disease in modern populations. More broadly, our data highlights the importance of defining the genetic architecture of disease across genetically diverse populations, and that disease insights derived from GWAS in one population may not translate to all affected populations.

Elevated risk of invasive group A streptococcal disease and host genetic variation in the human leucocyte antigen locus.

Invasive group A streptococcal (GAS) disease is uncommon but carries a high case-fatality rate relative to other infectious diseases. Given the ubiquity of mild GAS infections, it remains unclear why healthy individuals will occasionally develop life-threatening infections, raising the possibility of host genetic predisposition. Here, we present the results of a case-control study including 43 invasive GAS cases and 1540 controls. Using HLA imputation and linear mixed models, we find each copy of the HLA-DQA1*01:03 allele associates with a twofold increased risk of disease (odds ratio 2.3, 95% confidence interval 1.3-4.4, P = 0.009), an association which persists with classical HLA typing of a subset of cases and analysis with an alternative large control dataset with validated HLA data. Moreover, we propose the association is driven by the allele itself rather than the background haplotype. Overall this finding provides impetus for further investigation of the immunogenetic basis of this devastating bacterial disease.

Polyspecific Intravenous Immunoglobulin in Clindamycin-treated Patients With Streptococcal Toxic Shock Syndrome: A Systematic Review and Meta-analysis.

We evaluated the effect of intravenous immunoglobulin (IVIG) on mortality in clindamycin-treated streptococcal toxic shock syndrome using a meta-analysis. In association with IVIG, mortality fell from 33.7% to 15.7% with remarkable consistency across the single randomized and four nonrandomized studies.

Adherence to secondary antibiotic prophylaxis for patients with rheumatic heart disease diagnosed through screening in Fiji.

OBJECTIVES: Echocardiographic screening for rheumatic heart disease (RHD) can detect subclinical cases; however, adequate adherence to secondary antibiotic prophylaxis (SAP) is required to alter disease outcomes. We aimed to investigate the adherence to SAP among young people with RHD diagnosed through echocardiographic screening in Fiji and to investigate factors associated with adherence. METHODS: Patients diagnosed with RHD through echocardiographic screening in Fiji from 2006 to 2014 were included. Dates of benzathine penicillin G injections were collected from 76 health clinics nationally from December 2011 to December 2014. Adherence was measured using the proportion of days covered (PDC). Multivariate logistic regression analysis was used to identify characteristics associated with any adherence (≥1 injection received) and adequate adherence (PDC ≥0.80). RESULTS: Of 494 patients, 268 (54%) were female and the median age was 14 years. Overall, 203 (41%) had no injections recorded and just 33 (7%) had adequate adherence. Multivariate logistic regression showed increasing age (OR 0.93 per year, 95% CI 0.87-0.99) and time since diagnosis ≥1.5 years (OR 0.53, 95% CI 0.37-0.79) to be inversely associated with any adherence. Non-iTaukei ethnicity (OR 2.58, 95%CI 1.04-6.33) and urban residence (OR 3.36, 95% CI 1.54-7.36) were associated with adequate adherence, whereas time since diagnosis ≥1.5 years (OR 0.38, 95%CI 0.17-0.83) was inversely associated with adequate adherence. CONCLUSIONS: Adherence to SAP after screening in Fiji is currently inadequate for individual patient protection or population disease control. Secondary prevention should be strengthened before further screening can be justified.

Invasive streptococcal disease: a review for clinicians.

INTRODUCTION: Streptococci are a genus of Gram-positive bacteria which cause diverse human diseases. Many of these species have the potential to cause invasive infection resulting from the presence of bacteria in a normally sterile site. SOURCES OF DATA: Original articles, reviews and guidelines. AREAS OF AGREEMENT: Invasive infection by a streptococcus species usually causes life-threatening illness. When measured in terms of deaths, disability and cost, these infections remain an important threat to health in the UK. Overall they are becoming more frequent among the elderly and those with underlying chronic illness. New observational evidence has become available to support the use of clindamycin and intravenous immunoglobulin in invasive Group A streptococcal disease. AREAS OF CONTROVERSY: Few interventions for the treatment and prevention of these infections have undergone rigorous evaluation in clinical trials. For example, the role of preventative strategies such as screening of pregnant women to prevent neonatal invasive Group B streptococcal disease needs to be clarified. FUTURE PROSPECTS: Studies of invasive streptococcal disease are challenging to undertake, not least because individual hospitals treat relatively few confirmed cases. Instead clinicians and scientists must work together to build national and international networks with the aim of developing a more complete evidence base for the treatment and prevention of these devastating infections.

IFITM3 and susceptibility to respiratory viral infections in the community.

Interferon-inducible transmembrane proteins 1, 2, and 3 (IFITM 1,2, and 3) are viral restriction factors that mediate cellular resistance to several viruses. We have genotyped a possible splice-site altering single-nucleotide polymorphism (rs12252) in the IFITM3 gene in 34 patients with H1N1 influenza and severe pneumonia, and >5000 individuals comprising patients with community-acquired mild lower respiratory tract infection and matched controls of Caucasian ancestry. We found evidence of an association between rs12252 rare allele homozygotes and susceptibility to mild influenza (in patients attending primary care) but could not confirm a previously reported association between this single-nucleotide polymorphism and susceptibility to severe H1N1 infection.

Multi-ancestry meta-analysis of host genetic susceptibility to tuberculosis identifies shared genetic architecture.

The heritability of susceptibility to tuberculosis (TB) disease has been well recognized. Over 100 genes have been studied as candidates for TB susceptibility, and several variants were identified by genome-wide association studies (GWAS), but few replicate. We established the International Tuberculosis Host Genetics Consortium to perform a multi-ancestry meta-analysis of GWAS, including 14,153 cases and 19,536 controls of African, Asian, and European ancestry. Our analyses demonstrate a substantial degree of heritability (pooled polygenic h2 = 26.3%, 95% CI 23.7-29.0%) for susceptibility to TB that is shared across ancestries, highlighting an important host genetic influence on disease. We identified one global host genetic correlate for TB at genome-wide significance (p<5 × 10-8) in the human leukocyte antigen (HLA)-II region (rs28383206, p-value=5.2 × 10-9) but failed to replicate variants previously associated with TB susceptibility. These data demonstrate the complex shared genetic architecture of susceptibility to TB and the importance of large-scale GWAS analysis across multiple ancestries experiencing different levels of infection pressure.

Outcomes of rheumatic fever in Uganda: a prospective cohort study.

BACKGROUND: Rheumatic heart disease is the largest contributor to cardiac-related mortality in children worldwide. Outcomes in endemic settings after its antecedent illness, acute rheumatic fever, are not well understood. We aimed to describe 3-5 year mortality, acute rheumatic fever recurrence, changes in carditis, and correlates of mortality after acute rheumatic fever. METHODS: We conducted a prospective cohort study of Ugandan patients aged 4-23 years who were diagnosed with definite acute rheumatic fever using the modified 2015 Jones criteria from July 1, 2017, to March 31, 2020, enrolled at three rheumatic heart disease registry sites in Uganda (in Mbarara, Mulago, or Lira), and followed up for at least 1 year after diagnosis. Patients with congenital heart disease were excluded. Patients underwent annual review, most recently in August, 2022. We calculated rates of mortality and acute rheumatic fever recurrence, tabulated changes in carditis, performed Kaplan-Meier survival analyses, and used Cox regression models to identify correlates of mortality. FINDINGS: Data were collected between Sept 1 and Sept 30, 2022. Of 182 patients diagnosed with definite acute rheumatic fever, 156 patients were included in the analysis. Of these 156 patients (77 [49%] male and 79 (51%) female; data on ethnicity not collected), 25 (16%) died, 21 (13%) had a cardiac-related death, and 17 (11%) had recurrent acute rheumatic fever over a median of 4·3 (IQR 3·0-4·8) years. 16 (24%) of the 25 deaths occurred within 1 year. Among 131 (84%) of 156 survivors, one had carditis progression by echo. Moderate-to-severe carditis (hazard ratio 12·7 [95% CI 3·9-40·9]) and prolonged PR interval (hazard ratio 4·4 [95% CI 1·7-11·2]) at acute rheumatic fever diagnosis were associated with increased cardiac-related mortality. INTERPRETATION: These are the first contemporary data from sub-Saharan Africa on medium-term acute rheumatic fever outcomes. Mortality rates exceeded those reported elsewhere. Most decedents already had chronic carditis at initial acute rheumatic fever diagnosis, suggesting previous undiagnosed episodes that had already compounded into rheumatic heart disease. Our data highlight the large burden of undetected acute rheumatic fever in these settings and the need for improved awareness of and diagnostics for acute rheumatic fever to allow earlier detection. FUNDING: Strauss Award at Cincinnati Children's Hospital, American Heart Association, and Wellcome Trust.

High-resolution African HLA resource uncovers HLA-DRB1 expression effects underlying vaccine response.

How human genetic variation contributes to vaccine effectiveness in infants is unclear, and data are limited on these relationships in populations with African ancestries. We undertook genetic analyses of vaccine antibody responses in infants from Uganda (n = 1391), Burkina Faso (n = 353) and South Africa (n = 755), identifying associations between human leukocyte antigen (HLA) and antibody response for five of eight tested antigens spanning pertussis, diphtheria and hepatitis B vaccines. In addition, through HLA typing 1,702 individuals from 11 populations of African ancestry derived predominantly from the 1000 Genomes Project, we constructed an imputation resource, fine-mapping class II HLA-DR and DQ associations explaining up to 10% of antibody response variance in our infant cohorts. We observed differences in the genetic architecture of pertussis antibody response between the cohorts with African ancestries and an independent cohort with European ancestry, but found no in silico evidence of differences in HLA peptide binding affinity or breadth. Using immune cell expression quantitative trait loci datasets derived from African-ancestry samples from the 1000 Genomes Project, we found evidence of differential HLA-DRB1 expression correlating with inferred protection from pertussis following vaccination. This work suggests that HLA-DRB1 expression may play a role in vaccine response and should be considered alongside peptide selection to improve vaccine design.

Necrotising soft-tissue infections.

The incidence of necrotising soft-tissue infections has increased during recent decades such that most physicians might see at least one case of these potentially life-threatening infections in their career. Despite advances in care, necrotising soft-tissue infections are still associated with high morbidity and mortality, underlining a need for continued education of the medical community. In particular, failure to suspect necrotising soft-tissue infections, fuelled by poor awareness of the disease, promotes delays to first surgical debridement, amplifying disease severity and adverse outcomes. This Review will focus on practical approaches to management of necrotising soft-tissue infections including prompt recognition, initiation of specific management, exploratory surgery, and aftercare. Increased alertness and awareness for these infections should improve time to diagnosis and early referral to specialised centres, with improvement in the prognosis of necrotising soft-tissue infections.

Altered IL-6 signalling and risk of tuberculosis disease: a meta-analysis and Mendelian randomisation study.

IL-6 responses are ubiquitous in Mycobacterium tuberculosis (Mtb) infections, but their role in determining human tuberculosis (TB) disease risk is unknown. We used single nucleotide polymorphisms (SNPs) in and near the IL-6 receptor (IL6R) gene, focusing on the non-synonymous variant, rs2228145, associated with reduced classical IL-6 signalling, to assess the effect of altered IL-6 activity on TB disease risk. We identified 16 genome wide association studies (GWAS) of TB disease collating 17,982 cases of TB disease and 972,389 controls across 4 continents. Meta-analyses and Mendelian randomisation analyses revealed that reduced classical IL-6 signalling was associated with lower odds of TB disease, a finding replicated using multiple, independent SNP instruments and 2 separate exposure variables. Our findings establish a causal relationship between IL-6 signalling and the outcome of Mtb infection, suggesting IL-6 antagonists do not increase the risk of TB disease and should be investigated as adjuncts in treatment.

Population-based assessment of cardiovascular complications of rheumatic heart disease in Fiji: a record-linkage analysis.

OBJECTIVE: To determine population-based rates of non-fatal complications of rheumatic heart disease (RHD). DESIGN: Retrospective cohort study based on multiple sources of routine clinical and administrative data amalgamated by probabilistic record-linkage. SETTING: Fiji, an upper-middle-income country, where most of the population has access to government-funded healthcare services. PARTICIPANTS: National cohort of 2116 patients with clinically apparent RHD aged 5-69 years during 2008 and 2012. PRIMARY AND SECONDARY OUTCOME MEASURES: The primary outcome was hospitalisation for any of heart failure, atrial fibrillation, ischaemic stroke and infective endocarditis. Secondary outcomes were first hospitalisation for each of the complications individually in the national cohort as well as in hospital (n=1300) and maternity (n=210) subsets. Information on outcomes was obtained from discharge diagnoses coded in the hospital patient information system. Population-based rates were obtained using relative survival methods with census data as the denominator. RESULTS: Among 2116 patients in the national cohort (median age, 23.3 years; 57.7% women), 546 (25.8%) were hospitalised for an RHD complication, a substantial proportion of all cardiovascular admissions in the country during this period in those aged 0-40 years (heart failure, 210/454, 46.3%; ischaemic stroke 31/134, 23.1%). Absolute numbers of RHD complications peaked during the third decade of life with higher population-based rates in women compared with men (incidence rate ratio 1.4, 95% CI 1.3 to 1.6, p<0.001). Hospitalisation for any RHD complication was associated with substantially increased risk of death (HR 5.4, 95% CI 3.4 to 8.8, p<0.001), especially after the onset of heart failure (HR 6.6, 95% CI 4.8 to 9.1, p<0.001). CONCLUSIONS: Our study defines the burden of RHD-attributable morbidity in the general population of Fiji, potentially reflecting the situation in low-income and middle-income countries worldwide. Hospitalisation for an RHD complication is associated with markedly increased risk of death, re-emphasising the importance of effective early prevention.

Streptococcal skin infection and rheumatic heart disease.

PURPOSE OF REVIEW: In resource-limited tropical settings, both impetigo and rheumatic disease are endemic. The major cause of impetigo in these regions is the group A streptococcus and there is a growing body of opinion implicating impetigo in the pathogenesis of rheumatic fever and rheumatic heart disease (RHD). This potentially has major implications for control of these neglected diseases, which account for at least 350  000 deaths worldwide, annually. In this review, we summarize recent advances in the epidemiology of group A streptococcal skin disease and examine evidence for the relationship between group A streptococcal skin disease and rheumatic fever. RECENT FINDINGS: Detailed epidemiologic studies of impetigo, particularly among indigenous communities in the Pacific among whom rheumatic fever is endemic, find the disease remarkably prevalent. In contrast, group A streptococcal pharyngitis occurs no more frequently than in regions wherein rheumatic fever is now rare. Studies of molecular epidemiology reveal that overall there is a greater diversity of group A streptococcal strains in tropical regions, and skin-associated strains appear predominant. These skin strains may move between skin and throat, and there is increasing evidence of skin-associated strains being linked to cases of rheumatic fever. SUMMARY: The available data support the hypothesis that group A streptococcal impetigo plays a role in the pathogenesis of RHD. There is considerable scope to investigate this question through studies of pathogenesis, employing advances in both human and bacterial genetics, molecular immunology, and carefully designed trials aimed at control of impetigo.

Standardization of Epidemiological Surveillance of Rheumatic Heart Disease.

Rheumatic heart disease (RHD) is a long-term sequela of acute rheumatic fever (ARF), which classically begins after an untreated or undertreated infection caused by Streptococcus pyogenes (Strep A). RHD develops after the heart valves are permanently damaged due to ARF. RHD remains a leading cause of morbidity and mortality in young adults in resource-limited and low- and middle-income countries. This article presents case definitions for latent, suspected, and clinical RHD for persons with and without a history of ARF, and details case classifications, including differentiating between definite or borderline according to the 2012 World Heart Federation echocardiographic diagnostic criteria. This article also covers considerations specific to RHD surveillance methodology, including discussions on echocardiographic screening, where and how to conduct active or passive surveillance (eg, early childhood centers/schools, households, primary healthcare), participant eligibility, and the surveillance population. Additional considerations for RHD surveillance, including implications for secondary prophylaxis and follow-up, RHD registers, community engagement, and the negative impact of surveillance, are addressed. Finally, the core elements of case report forms for RHD, monitoring and audit requirements, quality control and assurance, and the ethics of conducting surveillance are discussed.

Standardization of Epidemiological Surveillance of Acute Rheumatic Fever.

Acute rheumatic fever (ARF) is a multiorgan inflammatory disorder that results from the body's autoimmune response to pharyngitis or a skin infection caused by Streptococcus pyogenes (Strep A). Acute rheumatic fever mainly affects those in low- and middle-income nations, as well as in indigenous populations in wealthy nations, where initial Strep A infections may go undetected. A single episode of ARF puts a person at increased risk of developing long-term cardiac damage known as rheumatic heart disease. We present case definitions for both definite and possible ARF, including initial and recurrent episodes, according to the 2015 Jones Criteria, and we discuss current tests available to aid in the diagnosis. We outline the considerations specific to ARF surveillance methodology, including discussion on where and how to conduct active or passive surveillance (eg, early childhood centers/schools, households, primary healthcare, administrative database review), participant eligibility, and the surveillance population. Additional considerations for ARF surveillance, including implications for secondary prophylaxis and follow-up, ARF registers, community engagement, and the impact of surveillance, are addressed. Finally, the core elements of case report forms for ARF, monitoring and audit requirements, quality control and assurance, and the ethics of conducting surveillance are discussed.

Standardization of Epidemiological Surveillance of Invasive Group A Streptococcal Infections.

Invasive group A streptococcal (Strep A) infections occur when Streptococcus pyogenes, also known as beta-hemolytic group A Streptococcus, invades a normally sterile site in the body. This article provides guidelines for establishing surveillance for invasive Strep A infections. The primary objective of invasive Strep A surveillance is to monitor trends in rates of infection and determine the demographic and clinical characteristics of patients with laboratory-confirmed invasive Strep A infection, the age- and sex-specific incidence in the population of a defined geographic area, trends in risk factors, and the mortality rates and rates of nonfatal sequelae caused by invasive Strep A infections. This article includes clinical descriptions followed by case definitions, based on clinical and laboratory evidence, and case classifications (confirmed or probable, if applicable) for invasive Strep A infections and for 3 Strep A syndromes: streptococcal toxic shock syndrome, necrotizing fasciitis, and pregnancy-associated Strep A infection. Considerations of the type of surveillance are also presented, noting that most people who have invasive Strep A infections will present to hospital and that invasive Strep A is a notifiable disease in some countries. Minimal surveillance necessary for invasive Strep A infection is facility-based, passive surveillance. A resource-intensive but more informative approach is active case finding of laboratory-confirmed Strep A invasive infections among a large (eg, state-wide) and well defined population. Participant eligibility, surveillance population, and additional surveillance components such as the use of International Classification of Disease diagnosis codes, follow-up, period of surveillance, seasonality, and sample size are discussed. Finally, the core data elements to be collected on case report forms are presented.

Modelling study of the ability to diagnose acute rheumatic fever at different levels of the Ugandan healthcare system.

OBJECTIVE: To determine the ability to accurately diagnose acute rheumatic fever (ARF) given the resources available at three levels of the Ugandan healthcare system. METHODS: Using data obtained from a large epidemiological database on ARF conducted in three districts of Uganda, we selected variables that might positively or negatively predict rheumatic fever based on diagnostic capacity at three levels/tiers of the Ugandan healthcare system. Variables were put into three statistical models that were built sequentially. Multiple logistic regression was used to estimate ORs and 95% CI of predictors of ARF. Performance of the models was determined using Akaike information criterion, adjusted R2, concordance C statistic, Brier score and adequacy index. RESULTS: A model with clinical predictor variables available at a lower-level health centre (tier 1) predicted ARF with an optimism corrected area under the curve (AUC) (c-statistic) of 0.69. Adding tests available at the district level (tier 2, ECG, complete blood count and malaria testing) increased the AUC to 0.76. A model that additionally included diagnostic tests available at the national referral hospital (tier 3, echocardiography, anti-streptolysin O titres, erythrocyte sedimentation rate/C-reactive protein) had the best performance with an AUC of 0.91. CONCLUSIONS: Reducing the burden of rheumatic heart disease in low and middle-income countries requires overcoming challenges of ARF diagnosis. Ensuring that possible cases can be evaluated using electrocardiography and relatively simple blood tests will improve diagnostic accuracy somewhat, but access to echocardiography and tests to confirm recent streptococcal infection will have the greatest impact.