Epidemiological Questions Research Articles

Paraneoplastic Sjogren’s syndrome in gastric cancer

In clinical practice, various masks of oncological diseases are often found. Some of them can manifest as a variety of syndromes or symptom complexes that resemble many non-oncologic diseases, including diffuse connective tissue diseases. In some cases, paraneoplastic syndrome facilitates diagnosing a malignant neoplasm in the early stages, but, unfortunately, can also mimic the tumor process by its more prominent manifestations, which lead to late establishment of the true cause of the disease, and therefore postpone specific treatment, creating significant clinical problems. Aim of the study was to reveal pathogenetic relationship between cancer and paraneoplastic syndrome on the example of our clinical observation. A clinical case of diagnosed paraneoplastic syndrome in the form of secondary Sjogren's syndrome, which developed long before the diagnosis of stomach cancer was made, as well as the results of clinical, instrumental, and laboratory examination of the patient, are presented. Questions of epidemiology, etiopathogenesis, and clinical picture of paraneoplastic syndrome are covered. The presented clinical case made it possible to outline the features of the course of paraneoplastic Sjogren's syndrome in gastric cancer and to identify a number of criteria for the diagnostic algorithm of this nosology. In particular, such criteria include general pathogenetic mechanisms, development only in malignant tumors, nonspecific clinical and laboratory manifestations, lack of parallelism with local symptoms of the tumor, the possibility of occurrence of paraneoplastic Sjogren's syndrome before development of local tumor symptoms and reappearance after its relapse. Oncologic diseases are characterized not only by specific symptoms characteristic for a certain organ damage (pain, bleeding, dysfunction, etc.), but also by a variety of nonspecific manifestations (fatigue, subfebrile temperature, weight loss, etc.) regardless of the nature, location and prevalence of the tumor process.

Estimation of causal effect measures with the R-package stdReg

Measures of causal effects play a central role in epidemiology. A wide range of measures exist, which are designed to give relevant answers to substantive epidemiological research questions. However, due to mathematical convenience and software limitations most studies only report odds ratios for binary outcomes and hazard ratios for time-to-event outcomes. In this paper we show how logistic regression models and Cox proportional hazards regression models can be used to estimate a wide range of causal effect measures, with the R-package stdReg. For illustration we focus on the attributable fraction, the number needed to treat and the relative excess risk due to interaction. We use two publicly available data sets, so that the reader can easily replicate and elaborate on the analyses. The first dataset includes information on 487 births among 188 women, and the second dataset includes information on 2982 women diagnosed with primary breast cancer.

Некоторые вопросы эпидемиологии и диагностики остеопороза.

Некоторые вопросы эпидемиологии и диагностики остеопороза.

Zika and Public Health: Understanding the Epidemiology and Information Environment.

Because Zika is a newly emerging infectious disease with little previous information known about it, there are many epidemiologic and clinical questions. The complexity of providing care to those who are at risk for infection or are already infected with Zika in this evidence-scarce environment cannot be understated. In this article, we provide an overview of the Zika virus (ZIKV) in the context of public health and pediatric health care. A broad public health focus is used to provide relevant information for addressing important questions about the epidemic and to facilitate communication with patients, parents, and caregivers within the current information environment. We explore issues regarding the epidemiology of the virus (including why ZIKV outbreaks are occurring), what has changed since the sporadic case reports before the outbreaks, why the true incidence is difficult to estimate, why attack rates vary by population and geography, and why the association between Zika and congenital Zika syndrome and Guillain-Barré syndrome have only come to light recently. Additionally, challenges related to the current information environment, traditional and informal information sources about the ZIKV, and examples of Zika public health communication campaigns are discussed. Importantly, we review the existing findings regarding the US population's Zika-related knowledge, attitudes, beliefs, and behavior by highlighting variations and gaps. We conclude by identifying related research questions that remain critical.

Does in situ melanoma really come before invasive melanoma? Descriptive epidemiology questions this relationship.

While the incidence rates for skin melanoma have in creased worldwide in the last decades, Breslow tumor thickness has decreased 1 . The incidence of in situ melanoma has also increased, and it doubled in the USA between 1988 and 2006 2 .These recent trends are in part due to the diffusion of early diagnosis 1,2 , which is based on the assumption that the detection of less inva sive lesions (i.e., those susceptible to more effective treatment ) will prevent the occurrence of the more in vasive and deadly ones. If the pattern for melanoma in dicated a worsening progression from in situ to invasive lesions -thin, first, then thick -the mean age at diagnosis for such lesions should increase accordingly. We retrieved melanoma cases incident between 2000 and2005fromtheTuscanyCancerRegistryarchive.This is a population-based cancer registry active in central Italy since 1985 on a population of about 1.2 million in habitants. Between 2000 and 2005, 1513 skin melanomas were newly diagnosed, 318 (21.0%) in situ and 1195 (79.0%) invasive. Among the latter, 607 (50.8%) were ≤1 mm , 410 (34.3%) >1 mm , while the Breslow thickness of 178 lesions (14.9%) could not be assessed. The mean ages of patients at diagnosis of melanomasin situ (57.69 years) and invasive melanomas (57.52) were similar (Student’s t-test, P = 0.87) . However, among in vasive melanomas, thin lesions (≤1 mm) were diag nosed at a younger age (54.03 years) than among in situ melanomas (P = 0.0014). By contrast, patients with > 1 mm thick melanomas were older at the time of diagno sis (61.95 years) than patients with in situ melanomas (Table 1 ). These results are mainly due to lentigo malig nant melanomas , which occur at a rather old age (mean age at diagnosis 71.3 years) and are more frequent among in situ (69/318, 21.6%) than among invasive melanomas (36/1195; 3.0%). According to the present data, in situ melanoma does not seem an obligate precursor of thin invasive melanoma, as it is diagnosed at an older age than inva sive melanoma ≤1 mm. Although most of the results are driven by lentigo maligna melanomas, descriptive epi demiology suggests different pathways for in situ and invasive melanomas, at least for thin ones. There may be 2 different in situ melanomas, some with an indolent behavior and others which are more aggressive ; micro melanomas invasive at diagnosis 3 may belong to the lat ter group.

Real world data in health technology assessments in kidney transplants in Germany: use of routinely collected data to address epidemiologic questions in kidney transplants in the AMNOG process in Germany.

Introduction: It is discussed whether real world data can be used in health technology assessment. Following it is of interest whether routinely collected data for quality assurance (QA) in the hospital sector is feasible to address epidemiologic questions in kidney transplantation in the AMNOG process in Germany. Objectives: To investigate the proportion of kidney transplants classified as from so-called standard criteria donors (SCD) and from expanded criteria donors (ECD) in Germany and to study the age distribution.Methods: After granted use by the Federal Joint Committee (G-BA), the data analysis was carried out by the AQUA institute, and a SPSS code was developed. Special challenge was the complex definition of SCD/ECD criteria that, in addition to donor age, takes into account combinations of donor diagnoses, creatinine, and cold ischemia time.Results: Age analyses could be performed in all patients. Median age of the adult transplant recipients in Germany was 54 years in 2012 as well as in 2013, range 18–85 and 18–82 years and a mean (SD) of 53 (14) and 52 (14) years, respectively. 63.5% (2012) and 62.5% (2013) of recipients were male. Classification in SCD/ECD transplants could be performed for 2,083 of 2,461 patients (85%; 2012) and for 1,795 of 2,079 patients (86%; 2013). Of all classifiable transplants 61.4% (2012) and 66.5% (2013) were SCD transplants. Total project time from the request to results was <6 months.Conclusions: The use of data routinely collected for QA in the hospital sector is feasible to address epidemiologic questions in kidney transplantation in the AMNOG process in Germany, which is basically following the systematic of an HTA process. All patients with kidney transplants are represented thus avoiding sampling error. Limitations include the availability of all necessary data in the QA data set. Within <6 months’ time with reasonable resources it was possible to meet timelines. The analyses were accepted by the authorities.

JavaScript Algorithm for Quantifier Elimination in Epidemiology.

Introduction:Quantifier Elimination gives us perfect insight into the most basic world of the computer, its origin, its primer functions and it basic operations. Carefully designed and programmed Algorithm for Quantifier Elimination makes the quantifier elimination from the quantified formulas much easier and much more comprehensiveAim:This paper explains how Quantifier Elimination algorithm can be used in the field of Biology, or to be more specific, in the field of Epidemiology.Material and methods:Exemplary formulas needed for the algorithm are all the formulas from the Mathematical Logic field. JavaScript programming language was used in order to program fast and effective algorithm for Quantifier Elimination.Results:Solving the certain problems from the field of Epidemiology using the Quantifier Elimination method, proved to be very successful in the past, because it made possible for the results to be extracted very fast. Doing the exact thing using the newer generation algorithm might be even more effective.Conclusion:The most basic concepts of Mathematical Logic can be implemented in order to solve the one of the most important questions in Epidemiology.

Advances from the nexus of animal behaviour and pathogen transmission: new directions and opportunities using contact networks

AbstractContact network models have enabled significant advances in understanding the influence of behaviour on parasite and pathogen transmission. They are an important tool that links variation in individual behaviour, to epidemiological consequences at the population level. Here, in our introduction to this special issue, we highlight the importance of applying network approaches to disease ecological and epidemiological questions, and how this has provided a much deeper understanding of these research areas. Recent advances in tracking host behaviour (bio-logging: e.g., GPS tracking, barcoding) and tracking pathogens (high-resolution sequencing), as well as methodological advances (multi-layer networks, computational techniques) started producing exciting new insights into disease transmission through contact networks. We discuss some of the exciting directions that the field is taking, some of the challenges, and importantly the opportunities that lie ahead. For instance, we suggest to integrate multiple transmission pathways, multiple pathogens, and in some systems, multiple host species, into the next generation of network models. Corresponding opportunities exist in utilising molecular techniques, such as high-resolution sequencing, to establish causality in network connectivity and disease outcomes. Such novel developments and the continued integration of network tools offers a more complete understanding of pathogen transmission processes, their underlying mechanisms and their evolutionary consequences.

Digital Epidemiology: Use of Digital Data Collected for Non-epidemiological Purposes in Epidemiological Studies

ObjectivesWe reviewed digital epidemiological studies to characterize how researchers are using digital data by topic domain, study purpose, data source, and analytic method.MethodsWe reviewed research articles published within the last decade that used digital data to answer epidemiological research questions. Data were abstracted from these articles using a data collection tool that we developed. Finally, we summarized the characteristics of the digital epidemiological studies.ResultsWe identified six main topic domains: infectious diseases (58.7%), non-communicable diseases (29.4%), mental health and substance use (8.3%), general population behavior (4.6%), environmental, dietary, and lifestyle (4.6%), and vital status (0.9%). We identified four categories for the study purpose: description (22.9%), exploration (34.9%), explanation (27.5%), and prediction and control (14.7%). We identified eight categories for the data sources: web search query (52.3%), social media posts (31.2%), web portal posts (11.9%), webpage access logs (7.3%), images (7.3%), mobile phone network data (1.8%), global positioning system data (1.8%), and others (2.8%). Of these, 50.5% used correlation analyses, 41.3% regression analyses, 25.6% machine learning, and 19.3% descriptive analyses.ConclusionsDigital data collected for non-epidemiological purposes are being used to study health phenomena in a variety of topic domains. Digital epidemiology requires access to large datasets and advanced analytics. Ensuring open access is clearly at odds with the desire to have as little personal data as possible in these large datasets to protect privacy. Establishment of data cooperatives with restricted access may be a solution to this dilemma.

Rabies elimination as a one-health model for the tropics: can this be a solution to the protracted problem in West Africa?

Introduction : the high number of annual rabies deaths in people and dogs in West Africa raises a fundamental epidemiological question among stakeholders. Rabies control program has successfully reduced rabies deaths in South America and Australia. Why is the programme not producing the desired effect in West Africa? What are the factors responsible for its failure? Methods : a round table discussion sought to answer the following questions: Why should emphasis be placed on human exposure through dog bites and on fatal human cases of rabies? Whereas, laboratory confirmation of exposure to rabies is infrequently done in West Africa, how can it be performed and why is it important? What should be done to prevent exposure or once exposure has occurred? How should the source of rabies exposure in people be identified? How can the source be located? What should be done and why? Results : frequently, the outbreak of rabies in dogs is identified as the source of human rabies outbreak; hence, it is important for something to be done by the veterinarians and by physicians in post-exposure care of dog bite victims. Vaccination of dogs should be performed not only where dogs have bitten people or exposed to other dogs, but should be universal, no matter how much it costs. Wandering dogs are classified as rabies risks and should be vaccinated.

The regional anesthesia for surgical correction of the malformation of upper extremities in pediatric

The article presents an analysis of the publications devoted to the problems of anesthesia to surgical procedures at the malformations of the upper extremity in children. The article reviews the questions of epidemiology, classification of upper extremity malformation, safety of anesthesia and the role of regional blockades in the structure of intraoperative and postoperative analgesia to surgical procedures at the malformations of the upper extremity in children. Children are more likely than adults to experience stress in the operating room and early postoperative period. Children are almost impossible to prepare psychologically for the upcoming anesthesia, surgical intervention, a sense of pain after it. Surgical correction of malformations of the upper limbs in children is characterized by multistage and high traumatism, which requires the search for adequate methods of anesthesia, capable of ensuring not only the absence of pain, but also the negative impact on the nervous system of little patients. The key to the application of regional anesthesia in young children is the need for sedation or general anesthesia. The use of ultrasound navigation and electrostimulation of peripheral nerves significantly increases the level of safety and success of their realization. At present, the questions about the duration of postoperative analgesia with the use of peripheral nerve blocks and the need for additional anesthesia in the early postoperative period have been little studied. The influence of the applied anesthesia technique on the state of young children in the postoperative period are requires further investigation.

Halitosis and associated factors in institutionalized elderly persons

Abstract Objective: to evaluate the prevalence of halitosis and associated factors in institutionalized elderly persons. Methods: a sectional study was performed with 268 elderly persons from 11 long-term care institutions in Natal in the northeast of Brazil. Data collection included an oral epidemiologic examination and questions about self-perception of oral health, as well as a consultation of medical records and the application of a questionnaire to the directors of the institutions. Halitosis was measured using the organoleptic test. The independent variables were oral, sociodemographic, institutional, general health and functional conditions. Bivariate analysis was performed using the Pearson chi-square test and Fisher's exact test, and the magnitude of effect was verified by the prevalence ratio for the independent variables in relation to the outcome, with a 95% confidence level. Results: the prevalence of halitosis was 26.1%, which was exhaled by the mouth in 98.57% of cases and by the nose in 10% of cases. Prevalence was 43% higher among non-white individuals (p=0.006); 65% higher among those living in non-profit institutions (p=0.039); 52% higher in elderly persons with oriented cognitive status (p=0.047); 41% higher in elderly persons with root caries (p=0.029); 62% higher in those who did not use dentures (p=0.046); 57% lower in edentulous persons (p&lt;0.001); and 73% higher in elderly individuals with tongue biofilm (p=0.001). Conclusion: The occurrence of halitosis in institutionalized elderly persons was similar to other studies, but there was an expressive number of extrabuccal cases and an association with oral health problems, as well as sociodemographic, institutional and functional factors.

Wildlife disease ecology from the individual to the population: Insights from a long-term study of a naturally infected European badger population.

Long-term individual-based datasets on host-pathogen systems are a rare and valuable resource for understanding the infectious disease dynamics in wildlife. A study of European badgers (Meles meles) naturally infected with bovine tuberculosis (bTB) at Woodchester Park in Gloucestershire (UK) has produced a unique dataset, facilitating investigation of a diverse range of epidemiological and ecological questions with implications for disease management. Since the 1970s, this badger population has been monitored with a systematic mark-recapture regime yielding a dataset of >15,000 captures of >3,000 individuals, providing detailed individual life-history, morphometric, genetic, reproductive and disease data. The annual prevalence of bTB in the Woodchester Park badger population exhibits no straightforward relationship with population density, and both the incidence and prevalence of Mycobacterium bovis show marked variation in space. The study has revealed phenotypic traits that are critical for understanding the social structure of badger populations along with mechanisms vital for understanding disease spread at different spatial resolutions. Woodchester-based studies have provided key insights into how host ecology can influence infection at different spatial and temporal scales. Specifically, it has revealed heterogeneity in epidemiological parameters; intrinsic and extrinsic factors affecting population dynamics; provided insights into senescence and individual life histories; and revealed consistent individual variation in foraging patterns, refuge use and social interactions. An improved understanding of ecological and epidemiological processes is imperative for effective disease management. Woodchester Park research has provided information of direct relevance to bTB management, and a better appreciation of the role of individual heterogeneity in disease transmission can contribute further in this regard. The Woodchester Park study system now offers a rare opportunity to seek a dynamic understanding of how individual-, group- and population-level processes interact. The wealth of existing data makes it possible to take a more integrative approach to examining how the consequences of individual heterogeneity scale to determine population-level pathogen dynamics and help advance our understanding of the ecological drivers of host-pathogen systems.

Revision rhinoplasty: physician-patient aesthetic and functional evaluation.

IntroductionApproximately 5–15% of patients submitted to rhinoplasty operations undergo revision surgery. Those patients have varied functional and aesthetic complaints that should receive a detailed assessment that includes all the expectations the patient had before the previous procedure.ObjectiveTo draw the profile of the main aesthetic-functional complaints reported by patients to be submitted to revision rhinoplasty and to correlate them with the internal and external objective nasal evaluation performed by the surgeon.MethodsA prospective study was conducted with 43 patients to be submitted to revision rhinoplasty and their respective surgeons, by applying a questionnaire about the patients’ epidemiological questions and subjective aesthetic-functional complaints as well as the respective functional deformities observed by the surgeons. Subsequently, these data were correlated with the purpose of observing the frequency of congruent reports between physicians and patients.ResultsThe presence of drooping tip and residual bridge hump were the patients’ main complaints, confirmed by the surgeons. The correlation between subjective obstructive symptoms and the intranasal evaluation performed by surgeons was shown to be present in 87.5% of the cases. Among the patients with respiratory symptoms, the main deformity identified was residual septal deviation in 56.25% of the cases.ConclusionThe drooping tip followed by residual hump were the main complaints reported by the patients and confirmed by the objective examination by the physicians. The presence of nasal obstructive complaints in 37.2% of the patients shows that greater attention needs to be paid to functional deformities during the first surgical procedure. The differences observed between patients’ complaints and surgeons’ evaluations confirm the need for detailed assessment and clarification to the patients regarding their expectations and actual surgical possibilities.

The Healthy Worker Survivor Effect: Target Parameters and Target Populations.

We offer an in-depth discussion of the time-varying confounding and selection bias mechanisms that give rise to the healthy worker survivor effect (HWSE). In this update of an earlier review, we distinguish between the mechanisms collectively known as the HWSE and the statistical bias that can result. This discussion highlights the importance of identifying both the target parameter and the target population for any research question in occupational epidemiology. Target parameters can correspond to hypothetical workplace interventions; we explore whether these target parameters' true values reflect the etiologic effect of an exposure on an outcome or the potential impact of enforcing an exposure limit in a more realistic setting. If a cohort includes workers hired before the start of follow-up, HWSE mechanisms can limit the transportability of the estimates to other target populations. We summarize recent publications that applied g-methods to control for the HWSE, focusing on their target parameters, target populations, and hypothetical interventions.

Using Viral Gene Sequences to Compare and Explain the Heterogeneous Spatial Dynamics of Virus Epidemics.

Rabies is an important zoonotic disease distributed worldwide. A key question in rabies epidemiology is the identification of factors that impact virus dispersion. Here we apply new analytical methods, based on phylogeographic reconstructions of viral lineage movement, to undertake a comparative evolutionary-epidemiological study of the spatial dynamics of rabies virus (RABV) epidemics in different hosts and habitats. We compiled RABV data sets from skunk, raccoon, bat and domestic dog populations in order to investigate the viral diffusivity of different RABV epidemics, and to detect and compare the environmental factors that impact the velocity of viral spread in continuous spatial landscapes. We build on a recently developed statistical framework that uses spatially- and temporally-referenced phylogenies. We estimate several spatial statistics of virus spread, which reveal a higher diffusivity of RABV in domestic dogs compared with RABV in other mammals. This finding is explained by subsequent analyses of environmental heterogeneity, which indicate that factors relating to human geography play a significant role in RABV dispersion in domestic dogs. More generally, our results suggest that human-related factors are important worldwide in explaining RABV dispersion in terrestrial host species. Our study shows that phylogenetically informed viral movements can be used to elucidate the factors that impact virus dispersal, opening new opportunities for a better understanding of the impact of host species and environmental conditions on the spatial dynamics of rapidly evolving populations.

Epidemiology of prostate and kidney cancer in the Aboriginal population of Canada: A systematic review

Prostate and kidney cancer rates in the Aboriginal population of Canada is a growing issue. A systematic review of prostate and kidney cancer epidemiology in the Aboriginal population of Canada was performed with international comparison and evaluation of present epidemiological disparities. PubMed, Medline, and Embase (from January 1946 to June 2016), relevant government-published reports, and the websites of organizations contributing to prostate or kidney cancer guidelines were searched. We included studies that informed any of the three epidemiological questions this review is focused on answering. Two systematic reviews, two meta-analyses, five literature reviews, and 21 single-study papers were included. The incidence and mortality rates of kidney cancer were elevated among Canadian Aboriginals when compared to the provincial or national population and to several international regions. No studies reported data on survival. Prostate cancer incidence, mortality, and survival rates were lower in Aboriginals provincially, nationally, and internationally, with incidence and survival reaching statistical significance. Elevated rate of risk factors for kidney cancer was a significant finding among Canadian Aboriginals. Aboriginals were screened for prostate cancer less than the general Canadian population, a trend also observed in the U.S. The elevated incidence and mortality of kidney cancer among Canadian Aboriginals is most likely attributable to the rise in lifestyle-based risk factors. Two correlations concerning prostate cancer are made. However, due to temporal and regional disparities in data, further investigation is required to elucidate these observations.

Integrating text analytics and statistical modelling to analyse kidney transplant immune suppression medication in registry data

ABSTRACT&#x0D; ObjectivesElectronic Health Records (EHRs) contain a wealth of routinely-collected data that could potentially be used to inform clinical decisions such as the choice between competing treatment regimens. Apart from structured data about diagnoses and biomarkers, these records often include unstructured data such as free-text medication prescriptions. Disjoint toolsets exist for structured and unstructured data, making it difficult to analyse datasets that comprise both structured and unstructured data. Representing free-text items in a structured and standardised format would enable their statistical analysis. The aim of this study was to develop a generic, analytical pipeline that integrates different tools for text analytics and statistical modelling, and to apply it to data from the UK Renal Registry (UKRR) to answer specific clinical and epidemiological questions on kidney transplant immune suppression.&#x0D; ApproachThe UKRR database comprises data from all renal units in England, Wales and Northern Ireland and consists of both structured and semi-structured data. Our workflow starts by using rules to extract medication regimen from free-text prescriptions, which is then automatically combined with structured patient's record. The data is then analysed for patterns of transplant immune suppression prescribing by specific centres across the UK.&#x0D; ResultsWe have developed an analytical pipeline for improving concordance between unstructured and structured medical records, combining new and established text analysis and subsequence analysis tools. Results of the study are underway and will be presented at the conference.&#x0D; ConclusionsWe have developed new framework that integrates tools for text analytics and statistical modelling, to facilitate the analysis of mixed structured and unstructured data. Our analysis of the UKRR data will help to compare immune suppressive treatment regimens, identify best practice, and explore the associations between transplant medication and transplant outcomes.

Fifty Years of Research in ARDS. The Epidemiology of Acute Respiratory Distress Syndrome. A 50th Birthday Review.

Since its first description 50 years ago, no other intensive care syndrome has been as extensively studied as acute respiratory distress syndrome (ARDS). Despite this extensive body of research, many basic epidemiologic questions remain unsolved. The lack of gold standard tests jeopardizes accurate diagnosis and translational research. Wide variation in the population incidence has been reported, making even simple estimates of the burden of disease problematic. Despite these limitations, there has been an increase in the understanding of pathophysiology and important risk factors both for the development of ARDS and for important patient-centered outcomes like mortality. In this Critical Care Perspective, we discuss the historical context of ARDS description and attempts at its definition. We highlight the epidemiologic challenges of studying ARDS, as well as other intensive care syndromes, and propose solutions to address them. We update the current knowledge of ARDS trends in incidence and mortality, risk factors, and recently described endotypes.

Detailed Knowledge About HIV Epidemiology and Transmission Dynamics and Their Associations With Preventive and Risk Behaviors Among Gay, Bisexual, and Other Men Who Have Sex With Men in the United States.

BackgroundGay, bisexual, and other men who have sex with men (GBMSM) in the United States remain disproportionately affected by human immunodeficiency virus (HIV). Yet their testing frequency is suboptimal and condomless anal sex (CAS) is increasing. Behavioral theories posit that information about HIV is a pivotal construct in individual risk reduction. However, measurements of knowledge have traditionally focused on ever hearing about HIV and being aware of the most common routes of spread.ObjectiveUsing a national Web-based sample of sexually active GBMSM, we sought to (1) quantify levels of detailed knowledge about HIV epidemiology and transmission dynamics, (2) describe variations in detailed knowledge levels across demographic strata, and (3) evaluate potential associations of increasing levels of detailed knowledge with HIV testing in the past year and engaging in CAS with a male partner in the past 3 months.MethodsGBMSM were recruited through a social networking website (Facebook) from August to September 2015 and asked 17 knowledge-based questions pertaining to the following 2 domains using a Web-based survey: HIV epidemiology (9 questions including statistics on incidence, prevalence, and distribution) and HIV transmission dynamics (8 questions including modes of spread and per-act transmission probabilities). Ordinal domain-specific indices of detailed knowledge were created for each respondent by summing their number of correct responses. Separate cumulative logit models were used to identify factors independently associated with each index, and multivariable logistic regression models were used to characterize associations with HIV testing history and recently engaging in CAS.ResultsOf the 1064 participants in our study, only half (49.62%, 528/1064) had been tested for HIV in the past year, and almost half (47.84%, 509/1064) had engaged in CAS with a male partner in the past 3 months. Majority scored 3 of 9 epidemiology questions correct (26.88%, 286/1064) and 5 of 8 transmission dynamics questions correct (25.00%, 266/1064). Participants younger than 35 years, of non-Hispanic non-white or Hispanic race and ethnicity, with lower educational levels, and who reported a sexual orientation other than homosexual or gay were significantly less knowledgeable about HIV transmission dynamics. Increasing levels of knowledge about this domain were independently associated with testing in the past year (adjusted odds ratio for each additional correct response: 1.10, 95% CI 1.01-1.20) but not with recent CAS. Increasing knowledge about HIV epidemiology was not associated with either outcome.ConclusionsIncreasing detailed knowledge about HIV epidemiology might not be as important as educating sexually active GBMSM regarding transmission dynamics. Researchers and practitioners designing prevention messages targeting GBMSM should bear in mind that not all knowledge is equal and that some aspects might have a greater positive impact than others. Future research to identify influential content and contemporary modes of delivery is needed.