Publications by authors named "Natarajan Karthik"

Background: U.S. FDA's Center for Biologics Evaluation and Research (CBER) Biologics Effectiveness and Safety (BEST) Initiative leverages large electronic health records and administrative claims data to conduct active surveillance for CBER-regulated products.

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Background: Respiratory syncytial virus vaccines first recommended for use during 2023 were efficacious against lower respiratory tract disease in clinical trials. Limited real-world data regarding respiratory syncytial virus vaccine effectiveness are available. To inform vaccine policy and address gaps in evidence from the clinical trials, we aimed to assess the effectiveness against respiratory syncytial virus-associated hospitalisations and emergency department encounters among adults aged at least 60 years.

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  • Pregnant individuals are at a higher risk for severe COVID-19, leading to current guidelines recommending updated vaccinations for everyone aged 6 months and older, regardless of pregnancy status.
  • A study evaluated COVID-19 vaccine effectiveness among pregnant people aged 18 to 45 from June 2022 to August 2023, finding that vaccine effectiveness during pregnancy was 52%, compared to 28% when vaccination was received less than 6 months before pregnancy and only 6% when received more than 6 months prior.
  • The findings suggest that pregnant individuals should remain up-to-date with recommended COVID-19 vaccinations for better protection against the virus.
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Background: A wealth of clinically relevant information is only obtainable within unstructured clinical narratives, leading to great interest in clinical natural language processing (NLP). While a multitude of approaches to NLP exist, current algorithm development approaches have limitations that can slow the development process. These limitations are exacerbated when the task is emergent, as is the case currently for NLP extraction of signs and symptoms of COVID-19 and postacute sequelae of SARS-CoV-2 infection (PASC).

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Precision medicine has the potential to provide more accurate diagnosis, appropriate treatment and timely prevention strategies by considering patients' biological makeup. However, this cannot be realized without integrating clinical and omics data in a data-sharing framework that achieves large sample sizes. Systems that integrate clinical and genetic data from multiple sources are scarce due to their distinct data types, interoperability, security and data ownership issues.

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  • The 2022-2023 influenza season in the U.S. experienced high hospitalization rates and early influenza activity, primarily driven by A(H3N2) viruses, with some A(H1N1)pdm09 cases.
  • A study using the test-negative design assessed the effectiveness of the influenza vaccine by comparing cases of influenza-positive patients to those who tested negative among adults with respiratory illness from October 2022 to March 2023.
  • The results showed moderate vaccine effectiveness of 44% for emergency department visits and 35% for hospitalizations, indicating that vaccination helps reduce the impact of influenza during a challenging season with other circulating respiratory viruses.
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  • The study explores using patient portal messaging to recruit underrepresented individuals for the All of Us Research Program, aiming to improve diversity in biomedical research.
  • A large-scale outreach was conducted at Columbia University, where over 59,000 patients were messaged, resulting in a 15.1% response rate and showing varying engagement levels among different racial and ethnic groups.
  • While the method increased outreach efficiency, the researchers found that underrepresented groups struggled more with initial consent and message engagement, highlighting the need for targeted strategies to enhance participation.
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Background: The study was aimed to evaluate gender difference and age & gender specific interaction of in-hospital outcomes of patients with ST elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).

Methods: This was a prospective cohort study of 1748 patients with STEMI undergoing primary PCI. The study was dichotomised according to gender to evaluate the difference in the outcome.

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Many of the existing composite social determinant of health indices, such as Area Deprivation Index, are constrained by their reliance on geographic approximations and American Community Survey data. This study builds on the body of literature around deprivation indices to construct an individual socioeconomic deprivation index (ISDI) within the NIH's All of Us Data Network by using weighted multiple correspondence analysis on SDOH data elements collected at the participant level. In this study, the correlation between ISDI and another area-approximated index is assessed to the extent possible, along with the changes in an AI models performance due to stratified sampling based on ISDI quintiles.

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Introduction: Electronic Health Records (EHR) are a useful data source for research, but their usability is hindered by measurement errors. This study investigated an automatic error detection algorithm for adult height and weight measurements in EHR for the All of Us Research Program (All of Us).

Methods: We developed reference charts for adult heights and weights that were stratified on participant sex.

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Background: Current hemovigilance methods generally rely on survey data or administrative claims data utilizing billing and revenue codes, each of which has limitations. We used electronic health records (EHR) linked to blood bank data to comprehensively characterize red blood cell (RBC) utilization patterns and trends in three healthcare systems participating in the U.S.

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  • Patients with drug-resistant epilepsy (DRE) need thorough neurodiagnostic evaluations, but there are significant delays in referrals and underutilization of surgery, particularly in diverse US settings.
  • This study seeks to analyze the rates and factors influencing neurodiagnostic evaluations for DRE patients across three different US cohorts using extensive medical data.
  • The findings reveal low rates of comprehensive evaluations among DRE patients, with only about 4.5% in the Medicaid cohort, 8.0% in the commercial insurance cohort, and 14.3% at Columbia University Medical Center.
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  • The CDC recommended the updated 2023-2024 COVID-19 vaccination (monovalent XBB.1.5) for everyone aged 6 months and older to help prevent severe disease caused by COVID-19.
  • For individuals with immunocompromising conditions, additional vaccine doses may be needed due to their increased risk of severe illness and potentially weaker vaccine responses.
  • Vaccine effectiveness for the updated dose was about 38% for hospitalized adults with immunocompromising conditions 7-59 days post-vaccination and 34% between 60-119 days, but only 18% of this high-risk group had received the updated vaccine.
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Background: Although psychiatric disorders have been associated with reduced immune responses to other vaccines, it remains unknown whether they influence COVID-19 vaccine effectiveness (VE). This study evaluated risk of COVID-19 hospitalization and estimated mRNA VE stratified by psychiatric disorder status.

Methods: In a retrospective cohort analysis of the VISION Network in four US states, the rate of laboratory-confirmed COVID-19-associated hospitalization between December 2021 and August 2022 was compared across psychiatric diagnoses and by monovalent mRNA COVID-19 vaccination status using Cox proportional hazards regression.

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  • In September 2023, the CDC recommended the updated 2023-2024 monovalent XBB.1.5 COVID-19 vaccine for everyone aged 6 months and older to help prevent COVID-19, including severe cases.
  • An analysis of vaccine effectiveness (VE) found that during the first 59 days after vaccination, the VE against COVID-19-related emergency department visits was 51%, which dropped to 39% after 60-119 days.
  • The updated COVID-19 vaccine showed increased protection, with VE against hospitalizations being 52% and 43% between two networks, supporting CDC's guidelines for vaccination.
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A 50-year-old female patient presented with class III angina for 6 months, positive stress test, and a prior CT angiogram suggestive of 3-vessel disease.

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  • The diversity of clinical notes in electronic health records (EHRs) highlights the need for standardization to improve data retrieval and integration, which is where the LOINC Document Ontology (DO) comes in, specifically designed for naming clinical documents.
  • This study evaluated the LOINC DO by mapping clinical note titles from five institutions, categorizing them into three classes based on how similar they are to LOINC DO codes, and developed an automated pipeline for this mapping that doesn't require accessing note content.
  • The automated mapping system, powered by various language models, demonstrated a high accuracy of 0.90, and the research compared its results with manual mappings to assess LOINC DO's effectiveness and identify opportunities for expanding
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Complete and accurate race and ethnicity (RE) patient information is important for many areas of biomedical informatics research, such as defining and characterizing cohorts, performing quality assessments, and identifying health inequities. Patient-level RE data is often inaccurate or missing in structured sources, but can be supplemented through clinical notes and natural language processing (NLP). While NLP has made many improvements in recent years with large language models, bias remains an often-unaddressed concern, with research showing that harmful and negative language is more often used for certain racial/ethnic groups than others.

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  • The 2022-2023 influenza season in the U.S. saw the highest rate of pediatric hospitalization since 2010-2011, primarily caused by Influenza A/H3N2 infections.
  • A study analyzed nearly 45,000 emergency department visits and hospitalizations for children aged 6 months to 17 years, focusing on the effectiveness of the influenza vaccine using a comparison between vaccinated and unvaccinated patients.
  • Results showed that vaccination significantly reduced the risk of influenza-related emergency visits and hospitalizations by approximately 40-48%, emphasizing the importance of flu shots in preventing severe illness in kids and teens.
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  • - A study analyzed COVID-19 vaccine effectiveness among 521,206 emergency department visits and 139,548 hospitalizations between June 2021 and September 2022, focusing on adults with disabilities.
  • - Of the encounters, only 2% had documented disabilities, but those individuals represent a significant portion of hospitalizations (12%).
  • - The results showed that COVID-19 vaccines worked similarly for both disabled and non-disabled adults, highlighting the need for disabled individuals to keep their vaccinations current to protect against severe disease.
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We carry out an analysis of gender differences in patterns of disease diagnosis across four large observational health datasets and find that women are routinely older when first assigned most diagnoses. Among 112 acute and chronic diseases, women experience longer lengths of time between symptom onset and disease diagnosis than men for most diseases regardless of metric used, even when only symptoms common to both genders are considered. These findings are consistent for patients with private as well as government insurance.

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Background: The epidemiology of coronavirus disease 2019 (COVID-19) continues to develop with emerging variants, expanding population-level immunity, and advances in clinical care. We describe changes in the clinical epidemiology of COVID-19 hospitalizations and risk factors for critical outcomes over time.

Methods: We included adults aged ≥18 years from 10 states hospitalized with COVID-19 June 2021-March 2023.

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  • - On June 19, 2022, the FDA approved mRNA COVID-19 vaccines for young children based on safety and efficacy data from trials, with Pfizer-BioNTech for ages 6 months-4 years and Moderna for ages 6 months-5 years.
  • - The CDC updated vaccine recommendations on December 9, 2022, including the use of bivalent vaccines for children aged 6 months and older, after assessing their effectiveness against hospital visits for COVID-19-like illness.
  • - Effectiveness of two Moderna doses was found to be 29%, while three Pfizer doses showed 43% effectiveness; however, children who received at least one bivalent dose had an 80% effectiveness in preventing
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The Research Program's Data and Research Center (DRC) was established to help acquire, curate, and provide access to one of the world's largest and most diverse datasets for precision medicine research. Already, over 500,000 participants are enrolled in , 80% of whom are underrepresented in biomedical research, and data are being analyzed by a community of over 2,300 researchers. The DRC created this thriving data ecosystem by collaborating with engaged participants, innovative program partners, and empowered researchers.

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  • Immunocompromised (IC) individuals face a higher risk of severe COVID-19 and have reduced vaccine effectiveness compared to non-immunocompromised (non-IC) individuals.
  • A study analyzed emergency department visits and hospitalizations among IC and non-IC adults, finding that vaccine effectiveness was significantly lower in IC patients, particularly for those who received 3 doses of mRNA vaccines or 1-2 doses of viral-vector vaccines.
  • Despite some protection from vaccines, the results indicate a pressing need for additional safeguards for IC adults, especially transplant recipients who showed the lowest vaccine effectiveness.
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