Samer El-Kamary

Samer El-Kamary
University of Maryland, Baltimore | UMB · Department of Epidemiology and Public Health

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80
Publications
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Publications

Publications (80)
Article
Many problems that appear in biomedical decision making, such as diagnosing disease and predicting response to treatment, can be expressed as binary classification problems. The support vector machine (SVM) is a popular classification technique that is robust to model misspecification and effectively handles high‐dimensional data. The relative cost...
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Abstract Background: As antiretroviral therapy (ART) programs expand access, there is an increase in burden to a healthcare system. These results are reduced provider-patient contact time and poor programmatic and patient outcomes. Qual‑ ity management ofers providers a standardized approach for addressing the appropriateness of care to be applied...
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Background: Clearance of hepatitis C virus (HCV) results in rapid changes in metabolic parameters early in direct-acting antiviral (DAA) therapy. Long-term changes after sustained virologic response (SVR) remain unknown. Methods: We investigated longitudinal changes in metabolic and inflammatory outcomes in chronic hepatitis C (CHC) patients: lo...
Article
Background Rapid decreases in activated CD4+ and CD8+ (HLA-DR + and CD38+ co-expressed) T-lymphocytes have been described within 1–2 weeks of initiating direct-acting antiviral (DAA) therapy among chronic Hepatitis C (CHC) patients. However, it is not known whether these changes are maintained past sustained virologic response (SVR), particularly i...
Article
Background: Risk of cognitive impairment is increased among persons with high or low body mass index (BMI) in HIV- and HIV+ populations in resource-rich settings. We examined this association among HIV+ patients in three resource-limited settings. Methods: This secondary analysis included data of 761 HIV+ volunteers pooled from 3 prospective coh...
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Background Convergence of tuberculosis (TB) and HIV epidemics is associated with higher morbidity and mortality risks and understanding their distribution across key demographic factors is essential for prevention and control. This analysis examines the prevalence of TB, HIV and TB-HIV coinfection across age and gender in patients with presumptive...
Article
Plasma HIV RNA level has been shown to correlate with HIV disease progression, morbidity, and mortality. We examined the association between levels of plasma HIV RNA and cognitive function among patients in Nigeria. A total of 179 HIV-1-infected participants with available plasma HIV RNA results and followed longitudinally for up to 2 years were in...
Preprint
Many problems that appear in biomedical decision making, such as diagnosing disease and predicting response to treatment, can be expressed as binary classification problems. The costs of false positives and false negatives vary across application domains and receiver operating characteristic (ROC) curves provide a visual representation of this trad...
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Current guidelines recommend only hepatitis C virus (HCV) risk-based screening during pregnancy. We examined screening practices at a major medical center and found inconsistent risk-based screening and the presence of HCV among women with no known risk factors. We make a case for implementation of universal HCV screening during pregnancy.
Article
Background: HIV-1 subtype has been shown to be associated with disease progression. We compared cognitive function between individuals infected with HIV-1 subtype G and CRF02_AG in Nigeria. Methods: For this cross-sectional study, samples were analyzed from 146 antiretroviral naïve participants. Genotypic analysis of plasma HIV RNA was performed...
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Background: Postpartum hepatitis C viral (HCV) load decline followed by spontaneous clearance has been previously described. Herein we identify predictors for viral decline in a cohort of HCV-infected postpartum women. Methods: Pregnant women at Cairo University were screened for anti-HCV antibodies and HCV RNA, and viremic women were tested for...
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Background: Tularemia is caused by Francisella tularensis, a gram-negative bacterium that has been weaponized as an aerosol. For protection of personnel conducting biodefense research, the United States Army required clinical evaluation of a new lot of tularemia live vaccine strain manufactured in accordance with Current Good Manufacturing Practic...
Article
Mononuclear cells play key roles in the pathogenic mechanisms leading to HIV-associated neurocognitive disorders (HANDs). We examined the association between HIV DNA within peripheral blood mononuclear cell (PBMC) subsets and HAND in Nigeria. PBMCs were collected at baseline from 36 antiretroviral naive participants. CD14+ cells and T&B lymphocyte...
Chapter
Viral hepatitis is caused by at least five viruses from five different families. Of those, hepatitis A and E viruses are acquired orally from fecally contaminated food, water or other sources. Hepatitis B, C and D viruses are mainly transmitted parenterally via blood, but also percutaneously, perinatally, and by sexual exposures. The public health...
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To date, there is no licensed Hepatitis C Virus (HCV) vaccine and what constitutes a protective immune response or correlate of protection against HCV infection is still vague. The Egyptian case of HCV is unique with a prevalence of ~15% among the general population and ~90 of the isolates belonging to genotype 4. This constitutes a great risk for...
Article
This is a quasi-experimental pre-post assessment study utilizing an anonymous self-administered questionnaire to assess Egyptian medical students’ awareness about responsible conduct of research (RCR) and research ethics. Students’ were assessed before and after an RCR awareness campaign. Our results showed that most of the pre-campaign respondents...
Article
This is a quasi-experimental pre-post assessment study utilizing an anonymous self-administered questionnaire to assess Egyptian medical students' awareness about responsible conduct of research (RCR) and research ethics. Students' were assessed before and after an RCR awareness campaign. Our results showed that most of the pre-campaign respondents...
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Background. Hepatitis C virus (HCV) is an underappreciated cause of pediatric liver disease, most frequently acquired by vertical transmission (VT). Current guidelines that include the option of screening infants for HCV RNA at 1–2 months are based on data prior to current real-time polymerase chain reaction (PCR)-based testing. Previous studies ha...
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Few studies have explored the informed consent process among research participants in developing countries. This study aimed to evaluate the informed consent process, therapeutic misconception and motivation for participation among Egyptians participating in clinical trials. In a cross-sectional qualitative pilot study 103 participants in 10 clinic...
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H5N1 influenza vaccination strategies that improve the immunological speed and cross-clade protection are desired. We compared the immunogenicity of a single 15 or 90 mcg dose of A/H5N1/Indonesia/05/05 (Clade 2) vaccine in adults who were previously primed with A/H5N1/Vietnam/1203/2004 (Clade 1) vaccine. High dose vaccine resulted in significantly...
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The Centers for Disease Control and Prevention (CDC) only recommends risk-based HCV screening for pregnant women in the United States. This study sought to determine the reliability of risk-based versus universal HCV screening for pregnant women in Egypt, a country with the world's highest HCV prevalence that also relies on risk-based screening, an...
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Background Chest-x-ray is routinely used in the diagnosis of smear negative tuberculosis (TB). This study assesses the incremental cost per true positive test of a point-of-care digital chest-x-ray, in the diagnosis of pulmonary mycobacterial infections among HIV patients with presumed tuberculosis undetected by smear microscopy.Methods Consecutive...
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Gambo Aliyu and colleagues describe an approach to eradicating polio in Northern Nigeria by engaging Muslim clerics in influencing community perceptions. Please see later in the article for the Editors' Summary
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To determine whether chemotherapy treatment at least 6 months prior to the detection of hepatic steatosis is associated with advanced hepatic fibrosis. Demographics, comorbid conditions, and laboratory data for cancer patients with hepatic steatosis were reviewed. The primary end point of this study was a low probability of fibrosis as calculated b...
Article
To explore associations between nonalcoholic fatty liver disease (NAFLD) and benign gastrointestinal and pancreato-biliary disorders. Patient demographics, diagnoses, and hospital outcomes from the 2010 Nationwide Inpatient Sample were analyzed. Chronic liver diseases were identified using International Classification of Diseases, the 9(th) Revisio...
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To examine whether adolescents' weight perception accuracy (WPA) was associated with extreme weight-management practices (EWPs) in differing body mass index (BMI) categories. WPA, overassessment, and underassessment were determined by comparing self-reported BMI and weight perception among US high-school students in the 2009 National Youth Risk Beh...
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Enterotoxigenic Escherichia coli (ETEC) is a primary cause of traveler's diarrhea for which there is no licensed vaccine. This phase 1 trial determined the safety and immunogenicity of a recombinantly produced double mutant heat-labile enterotoxin (dmLT) of ETEC. It was administered as a single oral dose of dmLT in escalating doses of 5 μg, 25 μg,...
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Objective. Data on pulmonary tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) complex in Nigeria are limited. We investigated species of MTB complex in TB cases from northern Nigeria. Methods. New TB suspects were enrolled, screened for HIV and their sputum samples were cultured after routine microscopy. Genotypes MTBC and MTBDRplus wer...
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Introduction: Reintroduction of Variola major as an agent of bioterrorism remains a concern. A shortened dosing schedule of Bavarian Nordic's (BN) IMVAMUNE(®) (modified vaccinia Ankara vaccine against smallpox) was compared to the currently recommended 0- and 28-day schedule for non-inferiority by evaluating the magnitude and kinetics of the immun...
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Nigeria is ranked in the top five countries for tuberculosis deaths worldwide. This study investigated the mycobacterial agents associated with presumptive clinical pulmonary tuberculosis (TB) in Nigeria and evaluated the pattern and frequency of mycobacterial infections over twelve calendar months period. Sputum samples from 1,603 consecutive new...
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Human leukocyte antigens class II play an important role in immune response against HCV. We investigated whether HLA class II alleles influence susceptibility to HCV infection and response to interferon therapy. HLA-DRB1 and -DQB1 loci were genotyped using PCR-SSO Luminex technology. According to our regimen, 41 (66%) of patients achieved sustained...
Article
Non-invasive fibrosis markers can distinguish between liver fibrosis stages in lieu of liver biopsy or imaging elastography. To develop a sensitive, non-invasive, freely-available algorithm that differentiates between individual liver fibrosis stages in chronic hepatitis C virus (HCV) patients. Chronic HCV patients (n = 355) at Cairo University Hos...
Article
Although the seroprevalence of hepatitis E virus (HEV) is approximately 80% in adult Egyptians living in rural areas, symptomatic HEV-caused acute viral hepatitis (AVH) is sporadic and relatively uncommon. To investigate the dichotomy between HEV infection and clinical AVH, HEV-specific immune responses in patients with symptomatic and asymptomatic...
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Objective To investigate the association between hepatitis C virus (HCV)-specific cell-mediated immunity (CMI) responses and viral clearance in children born to mothers infected with HCV. Study design A cross-sectional study of children from a mother-infant cohort in Egypt were enrolled to detect CMI responses to recombinant core and nonstructural...
Article
This paper examines the impact of a community-based intervention on the trends in the uptake of polio vaccination following a community mobilization campaign for polio eradication in northern Nigeria. Uptake of polio vaccination in high-risk communities in this region has been considerably low despite routine and supplemental vaccination activities...
Article
Noroviruses are the most frequent cause of acute gastroenteritis in humans of all ages. No vaccines are currently available. An intranasally delivered Norwalk (NV) virus-like particle (VLP) vaccine was recently shown to be well tolerated, immunogenic and to protect against infection in Phase 1 studies. Here, we examined B memory (B(M)) responses in...
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In epidemiologic research, incidence is often estimated from data arising from an imperfect diagnostic test performed at unequally spaced intervals over time. We developed a likelihood-based method to estimate incidence when disease status is measured imperfectly and assays are performed at multiple unequally spaced visits. We assumed conditional i...
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Hepatitis C virus (HCV)-specific cell-mediated immunity (CMI) has been reported among exposed individuals without viremia or seroconversion. Limited data are available regarding CMI among at-risk, seronegative, aviremic Egyptian health care workers (HCW), where HCV genotype 4 predominates. We investigated CMI responses among HCW at the National Liv...
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Little is known about the prevalence of hepatitis C virus (HCV) among healthcare workers (HCW) in Egypt, where the highest worldwide prevalence of HCV exists. The prevalence of HCV, hepatitis B virus and Schistosoma mansoni antibodies was examined in 842 HCWs at the National Liver Institute in the Nile Delta, where >85% of patients are HCV antibody...
Article
To provide a review of currently licensed enteric vaccines and their efficacy based on completed field trials. In this review, we provide a brief description of the epidemiology of the most common enteric infections, in both developing and industrialized countries. We also describe the types, dosage, age-eligibility, availability, and efficacies of...
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DNA vaccines are cost-effective and versatile, though intracellular delivery has been challenging in humans. Alternative delivery modalities such as electroporation have demonstrated improved immune responses, but are painful. In this single-center, double-blind, medical device trial, we evaluated the safety and tolerability of Easy Vax™ dermal ele...
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Hepatitis C virus (HCV) has a lower prevalence in children and knowledge is limited regarding the natural outcome of HCV infection in children. To study the risk factors of HCV acquisition and predictors of persistence in Egyptian children. Children, 1-9 years of age, were evaluated for acquisition of HCV (anti-HCV positive regardless of viraemia)...
Article
Liver-related mortality among those infected with hepatitis C virus (HCV) has been described, but little is known about non-liver-related mortality. Our objective was to determine HCV-associated all-cause, liver-, and non-liver-related mortality in the general US population. A prospective cohort study of 9378 nationally representative adults aged 1...
Article
The worldwide prevalence of hepatitis C virus (HCV) infection in pregnant women is estimated to be between 1 and 8% and in children between 0.05% and 5%. While parenteral transmission is still common in children living in developing countries, perinatal transmission is now the leading cause of HCV transmission in developed countries. The absence of...
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Cell-mediated immune (CMI) responses to hepatitis C virus (HCV) antigens in adults without seroconversion or viremia are biomarkers for prior transient infection. We investigated HCV-specific CMI responses in seronegative children living with HCV-infected siblings. Children 3-18 years of age living with HCV-infected siblings were screened for HCV a...
Article
Evidence regarding the health benefits of carotenoids is controversial. Effects of serum carotenoids and their interactions on mortality have not been examined in a representative sample of US adults. The objective was to examine whether serum carotenoid concentrations predict mortality among US adults. The study consisted of adults aged ≥20 years...
Article
To the Editor: In a recent issue of the American Journal of Gastroenterology, we read with great interest the study of Tung et al., which addresses the association between diabetes mellitus (DM), overweight, and hepatocellular carcinoma (HCC) (1). In our opinion, the lack of association described by the authors may be attributed to reverse causalit...
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Concerns have been expressed regarding the adequacy of ethics review systems in developing countries. Limited data are available regarding the structural and functional status of Research Ethics Committees (RECs) in the Middle East. The purpose of this study was to survey the existing RECs in Egypt to better understand their functioning status, per...
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A prospective study in three Egyptian villages (A, B and C) having a high prevalence of hepatitis C virus (HCV) infection examined incidence of community-acquired HCV infection in children; 2852 uninfected infants were prospectively followed from birth for up to 5.5 years. Fifteen seroconverted for either HCV antibodies and/or HCV-RNA (incidence of...
Article
We use the framework of coarsened data to motivate performing sensitivity analysis in the presence of incomplete data. To perform the sensitivity analysis, we specify pattern-mixture models to allow departures from the assumption of coarsening at random, a generalization of missing at random and independent censoring. We apply the concept of coarse...
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Although persistent transmission of hepatitis C virus (HCV) from infected mothers to their infants is reported in 4-8%, transient HCV perinatal infection also occurs. This prospective cohort study determined perinatal HCV infection- and early and late clearance-rates in 1,863 mother-infant pairs in rural Egyptian villages. This study found 15.7% an...
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Milk thistle or its purified extract, silymarin (Silybum marianum), is widely used in treating acute or chronic hepatitis. Although silymarin is hepatoprotective in animal experiments and some human hepatotoxic exposures, its efficacy in ameliorating the symptoms of acute clinical hepatitis remains inconclusive. In this study, our purpose was to de...
Article
We develop sample size formulas for studies aiming to test mean differences between a treatment and control group when all-or-none nonadherence (noncompliance) and selection bias are expected. Recent work by Fay, Halloran, and Follmann (2007, Biometrics 63, 465-474) addressed the increased variances within groups defined by treatment assignment whe...
Article
Despite difficulties associated with extreme variability and mutability of hepatitis C virus (HCV), several vaccines that prevent initial infection or viral persistence, or that clear viraemia in individuals with chronic HCV infections, are currently in development. At least one vaccine that may prevent chronic persistent infections will soon be av...
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A prospective cohort study of the incidence and risk factors for hepatitis C virus (HCV) infection was performed in 2171 pregnant women in three rural Egyptian villages who were HCV antibody (anti-HCV) and RNA (HCV-RNA) negative at baseline. During an average of 2.2 years follow up, 25 incident cases were observed, giving an estimated HCV incidence...