About

Robert Gross, MD, MSCE, is a Professor of Medicine in the Department of Infectious Diseases at the University of Pennsylvania's Perelman School of Medicine. He serves as an Attending Physician in Infectious Diseases at the Corporal Michael J. Crescenz Veterans Affairs Medical Center. His roles include Senior Scholar at the Center for Clinical Epidemiology and Biostatistics, Senior Fellow at the Leonard Davis Institute, and Co-Director of the Clinical Assessment Core at Penn Mental Health in AIDS Research Center. He is also a Senior Fellow at the Center for Public Health Initiatives and Co-Director of the Penn Center for AIDS Research, as well as Director of the International Core at the Penn Center for AIDS Research. His research expertise focuses on HIV clinical epidemiology, outcomes of HIV treatment, and adherence to therapy, including the development of methods to measure adherence. His clinical expertise is centered on HIV and infectious diseases. Dr. Gross's educational background includes a BA in Italian from Cornell University, an MD from Cornell University, and an MSCE in Pharmacoepidemiology from the University of Pennsylvania.

Research topics

• Medicine
• Internal medicine
• Biology
• Immunology
• Family medicine

Selected publications

• HIV Prevention Continuum Outcomes Following Implementation of a Municipal HIV Self-Testing Program

  AIDS and Behavior · 2025-08-14 · 2 citations

  articleOpen accessSenior author

  HIV self-testing (HIVST) must lead to engagement in the HIV status neutral continuum to maximize its benefits. The objective of this research was to determine the reach of a public health HIVST program, characterize the HIV prevention continuum following self-testing, and identify correlates associated with obtaining post-test care and discussing PrEP. We prospectively recruited individuals who obtained an HIVST through a municipal program in Philadelphia, a metropolitan area with high burden of HIV. We examined factors associated with seeing a provider after self-testing, and among those who saw a provider, factors associated with discussing PrEP. Between October 2022 and March 2024, 282 people met inclusion criteria. Men who have sex with men (MSM) comprised 28% of the study sample, 22% identified as Black cis-gender women, and 22% reported no prior HIV test. At one-month follow-up, 53% of respondents with HIV-negative/unknown status saw a provider, but less than a quarter of those discussed PrEP. Black individuals were more than twice as likely to see a provider compared with White individuals. Among those who saw a provider, MSM and Latinx/e individuals were more likely to discuss PrEP, while those assigned female at birth were less likely to discuss PrEP. Implementation of a municipal HIVST program can advance health equity by reaching priority populations, including previously untested persons. Although over half of participants saw a provider after self-testing, very few discussed or initiated PrEP. Interventions to promote linkage to care and PrEP uptake are needed to maximize the impact of HIVST.

  PublisherDOI

• Association of HIV status with infections complicating abortion in Botswana

  AIDS · 2025-05-08

  articleSenior author

  Women with HIV (WWH) were found to have an increased risk of abortion-related infection relative to women without HIV (WWoH) and those without HIV status documented. This relationship persisted even after accounting for factors such as mechanical injury on pelvic examination, a marker of the least safe methods of self-induction. Whether this complication in WWH is because of immunocompromise or behavioral characteristics requires additional investigation.

  PublisherDOI

• The association between systemic inflammation and albuminuria among people living with HIV: A cross-sectional study from Botswana

  Medicine · 2025-08-08 · 1 citations

  articleOpen access

  Treated human immunodeficiency virus (HIV) is associated with persistent systemic inflammation, even after many years of sustained viral suppression following initiation of antiretroviral therapy (ART). Albuminuria is common among people living with HIV (PLWH), but the impact of persistent systemic inflammation on outcome of albuminuria is not well understood. Thawed serum samples from PLWH who participated in an albuminuria prevalence study in Gaborone, Botswana, between January 2020 and March 2022, were selected randomly for a cross-sectional study of the link between inflammation and albuminuria. Systemic inflammation (interleukin [IL] 1β, IL 6, and soluble cluster of differentiation-163 [sCD163]) was assessed using enzyme linked immunosorbent assay, and albuminuria was reported as urinary albumin-creatinine ratio (ACR) (mg/g), as obtained from the parent study. The association between systemic inflammation and albuminuria was first explored by ACR quartiles, graphically using simple linear models, and then using general additive models for the adjusted analysis. The study population comprised 715 ART treated PLWH, with a mean age of 49.9 (SD 10.7) years, median HIV disease duration of 13.5 (IQR 8.7-16.7) years, and 398/715 (55.7%) were male. The relationship between log transformed ACR and sCD163 was linear, with regression coefficient β = 0.10, P-value = .02 but was nonlinear for log transformed IL-1β and IL-6, β = 0.10, P -value = .82 and β = -0.04, P-value = .36, respectively. In the final adjusted general additive models, sCD163 was not associated with ACR, P-value = .137. IL-1β, IL-6, and sCD163 were not associated with ACR among ART treated PLWH. Novel strategies to identify inflammatory pathways that may promote albuminuria among PLWH should consider other innovative and sensitive markers of both systemic and organ specific inflammation.

  PublisherDOI

• The role of alternative reinforcers in smoking outcomes among people with and without HIV.

  Psychology of Addictive Behaviors · 2025-06-05

  articleOpen access

  OBJECTIVE: People with HIV (PWH) smoke at higher rates than people without HIV (PWOH). Alternative reinforcers, or behaviors that replace (substitute reinforcers) or maintain (complementary reinforcers) smoking, are associated with smoking outcomes but have not been studied among PWH. This observational study assessed whether alternative reinforcers changed during a quit attempt among PWH and PWOH and whether the associations differed between groups. METHOD: The parent study included 274 participants (93 PWH and 181 PWOH) who sought treatment for smoking cessation in a 12-week program. The present analyses were limited to 173 (73 PWH and 100 PWOH) study completers. The primary outcomes were changes in substitute and complementary reinforcers at the end of treatment (EOT; week 12) measured using the Pleasant Events Schedule. We performed linear regressions in the overall sample and then stratified by HIV status for each alternative reinforcer. The time (baseline; week 0 vs. EOT) by smoking status at EOT (abstinent vs. nonabstinent) interaction was tested. RESULTS: = .04). CONCLUSIONS: Declines in complementary reinforcers were associated with smoking cessation outcomes among PWH. These findings partially support results from prior literature, suggesting that addressing complementary reinforcers during smoking cessation treatment may be crucial in improving quit rates among PWH. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

  PublisherDOI

• Training a Smoking Status Probabilistic Model Using Cotinine Levels in a Large Claims Database

  Nicotine & Tobacco Research · 2025-10-30

  articleOpen accessSenior author

  INTRODUCTION: Smoking status is an important confounder for many epidemiologic studies, yet it is not well documented in common sources of real-world data, including administrative claims. Probabilistic models can be used to create a proxy for smoking status, yet most published models have been trained using self-reported data. The objective of this study was to train a smoking status probabilistic model using cotinine values available in a large claims database. METHODS: Beneficiaries were included if they had at least one cotinine measurement and were categorized as a "current smoker" if their serum or plasma cotinine value was ≥5 ng/mL or urine cotinine value was ≥30 ng/mL. Predictors were collected across one year prior to the cotinine assessment date. The model was fit using logistic regression with stepwise forward selection. Model performance was assessed using discrimination and calibration. RESULTS: The final model yielded an area under the receiver operating characteristic curve of 0.77 (95%CI:0.75-0.78) and was well calibrated across most prediction deciles. The strongest predictors included diagnosis codes for smoking and drug abuse, and number of medications. The model was found to be highly specific, yet not sensitive at probability cutoffs ≥0.2. CONCLUSIONS: A smoking status model was developed and internally validated for application in claims data, using available cotinine values to define smoking status and found to have acceptable discrimination and calibration. The model is based on 26 predictors, fewer than other similar published smoking status models. External validation of the model should be a next step toward utilizing the model for epidemiological research. IMPLICATIONS: This study tests the utility of cotinine values to validate a smoking status probabilistic model, which has not been done in the literature to date. The results were robust to various cotinine levels used to define smoking status, per current guidance. The final model uses only 26 factors to predict smoking status, simplifying the application of the model in other claims databases.

  PublisherOA PDFDOI

• Systemic inequities, dignity, and trust in the context of HIV care: a qualitative analysis

  International Journal for Equity in Health · 2025-05-06

  articleOpen access

  Adherence and retention in care are key targets to achieve favorable health outcomes for people with HIV. Challenges with adherence and retention are pronounced for marginalized communities facing intersectional structural oppression. Community health worker delivery of Managed Problem Solving (MAPS+), an evidence-based behavioral intervention, has the potential to improve adherence and retention, yet understanding structural inequities affecting people with HIV is necessary to increase the likelihood of equitable implementation. The current study explores systemic inequities influencing HIV care adherence and retention, and approaches to address these challenges. We conducted semi-structured interviews with 13 clinics and 4 constituent groups: prescribing clinicians, non-prescribing clinical team members (e.g., medical case managers), clinic administrators, and policymakers. Through reflexive thematic analysis within a constructionist paradigm, we identified two key themes. The first elucidated experiences of systemic inequities such as access to resources, healthcare system navigation difficulties, power differentials, medical mistrust, intersectional stigma and potential patient burden associated with MAPS+. The second theme highlighted the ways in which staff and clinicians shoulder the burden of addressing inequities by approaching people with HIV with dignity and developing trusting relationships and how MAPS + can bolster this approach by partnering with and centering patient needs. While these individual and organizational efforts are valuable, ending the HIV epidemic requires structural changes to address systemic inequities directly. This research underscores the complex interplay between structural oppression and HIV care, calling for comprehensive approaches to achieve health equity.

  PublisherOA PDFDOI

• P-275. Risk Factors for Community Colonization with Extended-Spectrum Cephalosporin-Resistant <i>Enterobacterales</i> (ESCrE) among People with HIV in Botswana

  Open Forum Infectious Diseases · 2025-01-29

  articleOpen accessSenior author

  Abstract Background Extended-spectrum cephalosporin-resistant Enterobacterales (ESCrE) are a major global threat, and there is a significant gap in research on the burden and associated risk factors for ESCrE in low-and middle income countries(LMICs). This is particularly true for people with HIV (PWH), who make up a significant proportion of the population in sub-Saharan Africa. In Botswana, 20% of individuals aged 15-49 are PWH. The risk factors associated with ESCrE colonization, typically a precursor to infection, are important to understand as such infections can result in increased healthcare costs as well as high morbidity and mortality. Methods Within a larger regional surveillance study, 546 adults with HIV were recruited from clinics and communities in 3 districts and underwent interviews and rectal sampling. ESCrE was defined as Enterobacterales demonstrating non-susceptibility to ceftriaxone or ceftazidime. Results 27% of participants screened positive for ESCrE colonization. The mean CD4 count was 635 cells/mm3 (SD± 267). Table 1 describes the demographics of the participants with and without ESCrE colonization. Escherichia coli was the most commonly isolated ESCrE (146/174; 84%). Bivariate and multivariate analysis was used to determine risk factors associated with ESCrE colonization (Table 2). Recent hospitalization and certain geographic locations were independent risk factors for ESCrE colonization. Recent antibiotic use had an elevated OR for ESCrE colonization that did not achieve statistical significance in adjusted analysis. Conclusion These results add to the limited data on risk factors associated with ESCrE colonization in PWH. Hospitalization is an independent risk factor for colonization despite controlling for antibiotic use, which suggests the need for further investigation into hospital-specific factors that contribute to ESCrE colonization. Further research is needed to understand the geographic differences in ESCrE colonization in this setting. As LMICs with high HIV burdens build capacity for antimicrobial stewardship and infection prevention infrastructure in healthcare, research on unique potential mechanisms that result in multi-drug resistant colonization in PWH may impact strategies and priorities to combat antimicrobial resistance. Disclosures Robert Gross, MD, MSCE, Pfizer Inc: DSMB member for drug unrelated to study

  PublisherDOI

• Colonization with antibiotic resistant bacteria in communities and hospitals across six countries, including Bangladesh, Botswana, Chile, Guatemala, India, and Kenya

  Scientific Reports · 2025-07-01 · 7 citations

  articleOpen access

  Abstract The recognized burden of antimicrobial resistance (AR) is greatest in low- and middle-income countries (LMICs), but limitations in surveillance preclude accurate estimates of AR. We aimed to evaluate colonization in communities and hospitals across six LMICs for two clinically-important pathogens: extended-spectrum cephalosporin-resistant Enterobacterales (ESCrE) and carbapenem-resistant Enterobacterales (CRE). Participants in hospitals and communities provided rectal swabs or stool samples for ESCrE and CRE identification. Isolates recovered from selective agars underwent confirmatory identification and antibiotic susceptibility testing (AST) using Vitek ® 2, MALDI-TOF, and/or disc diffusion testing. ESCrE and CRE were defined based on established breakpoints of phenotypic resistance to third-generation cephalosporins and carbapenems, respectively, to calculate prevalence of colonization. Community prevalence estimates were weighted to account for sampling design differences. A total of 10,139 participants across the 6 countries provided samples; 63% were females with a median age of 35 years (range: 0–99). Colonization with ESCrE in hospitals was high in all sites (range 34–84%). In communities, ESCrE colonization ranged from 22 to 77%. Prevalence of CRE colonization in hospitals ranged from 7 to 36% and in communities ranged from &lt; 1 to 14%. These findings reveal a high burden of AR colonization in LMICs in both communities and hospitals. Cost-effective strategies to reduce AR colonization burden are needed in LMICs.

  PublisherOA PDFDOI

• A formative study to develop nudges informed by behavioral economics to increase engagement with tobacco treatment among people who smoke receiving care for HIV

  Drug and Alcohol Dependence Reports · 2025-06-25 · 1 citations

  articleOpen access

  The rate of tobacco use among people with HIV (PWH) is >2 fold higher vs. the general population and accounts for more life years lost than the virus. Yet, evidence-based tobacco treatments are uncommonly offered by clinicians or used by PWH. Biases informed by behavioral economics concerning tobacco treatments may drive this practice gap. This formative study tested nudges in the form of messages that target four behavioral economic biases – status quo, availability, omission, and focusing effect – to determine which message would be most strongly associated with PWH willingness to use or clinician referral for tobacco treatment; 19 clinicians and 75 PWH assessed pair-wise comparisons of the four messages with instructions to select the message that, if sent via text or a patient portal, or via the electronic medical record (EMR) at a clinic visit, would increase willingness to use or provide a referral for tobacco treatment. There were significant differences in reported preference across the messages among PWH (χ 2 [3]=24.79, p <0.001) and clinicians ( χ 2 [3]=33.85 , p <0.001). The message that addressed focusing effect bias was most preferred for increasing use and referral for tobacco treatment among PWH (29%) and clinicians (38%). A message that addressed focusing effect bias was associated with greater interest in the use of or referral for tobacco treatment within HIV care. These results can help design a clinical trial to test the effectiveness of these messages within the clinical workflow for their effects on actual use of and referral for tobacco treatment for PWH. • Messages targeting focusing effect bias related to tobacco treatment in HIV care. • Behavioral economics can provide a framework for implementing tobacco treatment. • Results can guide subsequent implementation science studies of tobacco treatment.

  PublisherDOI

• Feasibility, Acceptability, and Fidelity of the Take Steps HIV Prevention Intervention

  Journal of Adolescent Health · 2025-02-07

  articleOpen access
  PublisherOA PDFDOI

Recent grants

• Molecular & Translational Immunotechnology Core

  NIH · $36.7M · 1999–2029

• NIH Grant R01MH067498

  NIH · $2.6M · 2011

• Testing Novel Pharmacogenetic and Adherence Optimization Treatments to Improve the Effectiveness of Smoking Cessation Treatments for Smokers with HIV

  NIH · $3.4M · 2019–2026

• NIH Grant R01GM036057

  NIH · $356k · 1989

• NIH Grant R01MH080701

  NIH · $2.6M · 2015

Frequent coauthors

• Andrew P. Steenhoff

  Children's Hospital of Philadelphia

  78 shared

• Warren B. Bilker

  University of Pennsylvania

  58 shared

• Gregory P. Bisson

  55 shared

• Surbhi Grover

  53 shared

• Elizabeth Lowenthal

  University of Pennsylvania

  51 shared

• Yehoda M. Martei

  University of Pennsylvania

  48 shared

• Angela DeMichele

  University of Pennsylvania

  45 shared

• Tlotlo Ralefala

  University of Botswana

  45 shared

Education

• MSCE, Biostatistics and Epidemiology

  University of Pennsylvania

  2000

• MD

  Weill Cornell Medicine

  1991

• BA

  Cornell University

  1986