Early adopters of doxycycline as post-exposure prophylaxis to prevent bacterial sexually transmitted infections in a real-world clinical setting.

OBJECTIVES: Doxycycline as post-exposure prophylaxis (DoxyPEP) is a novel prevention approach which has demonstrated efficacy in preventing bacterial sexually transmitted infections (STIs) in men who have sex with men (MSM) and transgender women (TGW) including people who are living with HIV and those on HIV pre-exposure prophylaxis (PrEP). We evaluated patient knowledge and interest in DoxyPEP, as well as early adopters of its use. METHODS: In 2023, patients presenting for HIV and STI services at a primary care and sexual health clinic were asked about DoxyPEP knowledge, interest and use. Bivariate and multivariate analyses were used to evaluate demographics and behaviours associated with these outcomes. RESULTS: A total of n=421 people presented for care. Of these, 314 were MSM/TGW. Fifteen percent were Black/African-American, and 21% were Hispanic/Latino. A total of 50% of MSM/TGW had heard of DoxyPEP, 49% were interested and 18% reported prior DoxyPEP use. Having a history of STI infection ever (adjusted OR (aOR) 5.95, 95% CI 2.69 to 13.13) and in the past 12 months (aOR 2.99, 95% CI 1.56 to 5.72) were both associated with DoxyPEP use. Individuals who had ever used HIV PrEP had nearly three times the odds of ever taking DoxyPEP (aOR 2.88, 95% CI 1.56 to 5.30). There was no association between the use of DoxyPEP and race, ethnicity or HIV status. CONCLUSIONS: Among MSM and TGW, there is already significant awareness, interest and use of DoxyPEP to prevent bacterial STIs. Public health efforts should focus on improving access and delivery of this STI prevention intervention to MSM and TGW.

Implementation of Point of Care Sexually Transmitted Infections Testing in a Community Clinic Setting.

ABSTRACT: The rates of sexually transmitted infections (STIs) in the United States, including chlamydia and gonorrhea, are rising. Point-of-care (POC) testing could increase access to testing and treatment. This evaluation found POC STI testing to be concordant with the results of traditional laboratory testing for 100% of patients who were tested. Ninety-five percent of the patients reported being satisfied with the experience, and 66% preferred it to traditional laboratory testing. The most commonly reported reason for preferring the test was the short amount of time it took to receive results. However, insurance reimbursed less than 30% of what was billed for the POC tests. Low insurance reimbursement rates could be a barrier to implementation long-term financial sustainability of POC STI testing.

African American Clergy Recommendations to Enhance the Federal Plan to End the HIV Epidemic: A Qualitative Study.

African Americans in the southern United States continue to be disproportionately affected by HIV. Although faith-based organizations (FBOs) play important roles in the social fabric of African American communities, few HIV screening, care, and PrEP promotion efforts harness the power of FBOs. We conducted 11 focus groups among 57 prominent African American clergy from Arkansas, Mississippi, and Alabama. We explored clergy knowledge about the Ending the HIV Epidemic: A Plan for America (EHE); normative recommendations for how clergy can contribute to EHE; and how clergy can enhance the HIV care continua and PrEP. We explored how clergy have responded to the COVID-19 crisis, and lessons learned from pandemic experiences that are relevant for HIV programs. Clergy reported a moral obligation to participate in the response to the HIV epidemic and were willing to support efforts to expand HIV screening, treatment, PrEP and HIV care. Few clergy were familiar with EHE, U = U and TasP. Many suggested developing culturally tailored messages and were willing to lend their voices to social marketing efforts to destigmatize HIV and promote uptake of biomedical interventions. Nearly all clergy believed technical assistance with biomedical HIV prevention and care interventions would enhance their ability to create partnerships with local community health centers. Partnering with FBOs presents important and unique opportunities to reduce HIV disparities. Clergy want to participate in the EHE movement and need federal resources and technical assistance to support their efforts to bridge community activities with biomedical prevention and care programs related to HIV. The COVID-19 pandemic presents opportunities to build important infrastructure related to these goals.

A Community-Adapted Approach to SARS-CoV-2 Testing for Medically Underserved Populations, Rhode Island, USA.

We developed a testing program for severe acute respiratory syndrome coronavirus 2 in an urban Latinx neighborhood in Providence, Rhode Island, USA. Approximately 11% of Latinx participants (n = 180) tested positive. Culturally tailored, community-based programs that reduce barriers to testing help identify persons at highest risk for coronavirus disease.

Time Since Infection and Risks of Future Disease for Individuals with Mycobacterium tuberculosis Infection in the United States.

BACKGROUND: Risk of tuberculosis (TB) declines over time since Mycobacterium tuberculosis infection, but progression to clinical disease is still possible decades later. In the United States, most TB cases result from the progression of latent TB infection acquired over 2 years ago. METHODS: We synthesized evidence on TB natural history and incidence trends using a transmission-dynamic model. For the 2020 US population, we estimated average time since infection and annual, cumulative, and remaining lifetime risks of progression to TB, by nativity and age. RESULTS: For a newly infected adult with no other risk factors for progression to TB, estimated rates of progression declined from 38 (95% uncertainty interval: 33, 46) to 0.38 (0.32, 0.45) per 1000 person-years between the first and 25th year since infection. Cumulative risk over 25 years from new infection was 7.9% (7.0, 8.9). In 2020, an estimated average age of individuals with prevalent infection was 62 (61, 63) for the US-born population, 55 (54, 55) for non-US-born, and 57 (56, 58) overall. Average risks of developing TB over the remaining lifetime were 1.2% (1.0, 1.4) for US-born, 2.2% (1.8, 2.6) for non-US-born, and 1.9% (1.6, 2.2) for the general population. Risk estimates were higher for younger age groups. CONCLUSIONS: Our analysis suggests that, although newly infected individuals face appreciable lifetime TB risks, most US individuals with latent TB infection were infected long ago, and face low future risks of developing TB. Better approaches are needed for identifying recently infected individuals and those with elevated progression risks.

Modeling the Cost-Effectiveness of Express Multisite Gonorrhea Screening Among Men Who Have Sex With Men in the United States.

BACKGROUND: Men who have sex with men (MSM) experience high rates of gonococcal infection at extragenital (rectal and pharyngeal) anatomic sites, which often are missed without asymptomatic screening and may be important for onward transmission. Implementing an express pathway for asymptomatic MSM seeking routine screening at their clinic may be a cost-effective way to improve extragenital screening by allowing patients to be screened at more anatomic sites through a streamlined, less costly process. METHODS: We modified an agent-based model of anatomic site-specific gonococcal infection in US MSM to assess the cost-effectiveness of an express screening pathway in which all asymptomatic MSM presenting at their clinic were screened at the urogenital, rectal, and pharyngeal sites but forewent a provider consultation and physical examination and self-collected their own samples. We calculated the cumulative health effects expressed as gonococcal infections and cases averted over 5 years, labor and material costs, and incremental cost-effectiveness ratios for express versus traditional scenarios. RESULTS: The express scenario averted more infections and cases in each intervention year. The increased diagnostic costs of triple-site screening were largely offset by the lowered visit costs of the express pathway and, from the end of year 3 onward, this pathway generated small cost savings. However, in a sensitivity analysis of assumed overhead costs, cost savings under the express scenario disappeared in the majority of simulations once overhead costs exceeded 7% of total annual costs. CONCLUSIONS: Express screening may be a cost-effective option for improving multisite anatomic screening among US MSM.

The impact of financial incentives on SNAP transactions at mobile produce markets.

BACKGROUND: Offering financial incentives promotes increases in fruit and vegetable purchases in farmers' markets and supermarkets. Yet, little is understood about whether food-insecure adults purchase more fruits and vegetables as a result of receiving financial incentives in mobile produce market settings. METHODS: In 2018-2019, Food on the Move provided a 50% discount to customers using Supplemental Nutrition Assistance Program (SNAP) benefits to purchase fruit and vegetables from 16 market locations in Rhode Island (n = 412 market occasions). We used mixed multivariable linear regression to estimate the difference in total dollar sales per transaction per month between SNAP transactions and non-SNAP transactions. We also estimated the difference in out-of-pocket dollar sales per transaction per month between SNAP and non-SNAP transactions, less the 50% discount. This reflects the actual amount spent on fresh fruits and vegetables purchased per visit. In both models, we controlled for the number of market sites per month, with fixed effects for quarter and year. We estimated random intercept variance for date of transaction and market site to adjust for clustering. RESULTS: In 2018-2019, the majority of market transactions (total n = 13,165) were SNAP transactions [n = 7.988 (63.0%)]. On average, customers spent $17.38 (SD = 16.69) on fruits and vegetables per transaction per month. However, customers using SNAP benefits spent significantly more on FVs per transaction per month [$22.01 (SD = 17.97)] compared to those who did not use SNAP benefits [9.81 (SD = 10.68)] (ß = $10.88; 95% CI: 10.18, 11.58). Similarly, out-of-pocket dollar sales per SNAP transaction per month (i.e., less the 50% discount) were significantly higher [$11.42 (SD = 9.44)] relative to non-SNAP transactions [$9.40 (SD = 9.33)] (ß = $1.85; 95% CI: 1.44, 2.27). CONCLUSIONS: Financial incentives contributed to higher fruit and vegetable purchases among low-income customers who shop at mobile produce markets by making produce more affordable. Higher spending on fruits and vegetables may promote healthy diet behaviors and reduce chronic disease risk among food-insecure adults.

Impact of Effective Global Tuberculosis Control on Health and Economic Outcomes in the United States.

Rationale: Most U.S. residents who develop tuberculosis (TB) were born abroad, and U.S. TB incidence is increasingly driven by infection risks in other countries.Objectives: To estimate the potential impact of effective global TB control on health and economic outcomes in the United States.Methods: We estimated outcomes using linked mathematical models of TB epidemiology in the United States and migrants' birth countries. A base-case scenario extrapolated country-specific TB incidence trends. We compared this with scenarios in which countries achieve 90% TB incidence reductions between 2015 and 2035, as targeted by the World Health Organization's End TB Strategy ("effective global TB control"). We also considered pessimistic scenarios of flat TB incidence trends in individual countries.Measurements and Main Results: We estimated TB cases, deaths, and costs and the total economic burden of TB in the United States. Compared with the base-case scenario, effective global TB control would avert 40,000 (95% uncertainty interval, 29,000-55,000) TB cases in the United States in 2020-2035. TB incidence rates in 2035 would be 43% (95% uncertainty interval, 34-54%) lower than in the base-case scenario, and 49% (95% uncertainty interval, 44-55%) lower than in 2020. Summed over 2020-2035, this represents 0.8 billion dollars (95% uncertainty interval, 0.6-1.0 billion dollars) in averted healthcare costs and $2.5 billion dollars (95% uncertainty interval, 1.7-3.6 billion dollars) in productivity gains. The total U.S. economic burden of TB (including the value of averted TB deaths) would be 21% (95% uncertainty interval, 16-28%) lower (18 billion dollars [95% uncertainty level, 8-32 billion dollars]).Conclusions: In addition to producing major health benefits for high-burden countries, strengthened efforts to achieve effective global TB control could produce substantial health and economic benefits for the United States.

An Emergency Department Delirium Screening and Management Initiative: The Development and Refinement of the SCREENED-ED Intervention.

The current article describes an intervention aimed at emergency department (ED) nurses and physicians that was designed to address the challenges of managing delirium in the ED environment. The intervention development process followed the Medical Research Council principles paired with a user-centered design perspective. Expert clinicians and nursing staff were involved in the development process. As a result, the SCREENED-ED intervention includes four major components: screening for delirium, informing providers, an acronym (ALTERED), and documentation in the electronic health record. The acronym "ALTERED" includes seven key elements of delirium management that were considered the most evidence-based, relevant, and practical for the ED. Nurses are at the frontline of delirium recognition and management and the SCREENED-ED intervention with the ALTERED acronym holds the potential to improve nursing care in this complex clinical setting. [Journal of Gerontological Nursing, 47(12), 13-17.].

Potential for Point-of-Care Tests to Reduce Chlamydia-associated Burden in the United States: A Mathematical Modeling Analysis.

BACKGROUND: Point-of-care testing (POCT) assays for chlamydia are being developed. Their potential impact on the burden of chlamydial infection in the United States, in light of suboptimal screening coverage, remains unclear. METHODS: Using a transmission model calibrated to data in the United States, we estimated the impact of POCT on chlamydia prevalence, incidence, and chlamydia-attributable pelvic inflammatory disease (PID) incidence, assuming status quo (Analysis 1) and improved (Analysis 2) screening frequencies. We tested the robustness of results to changes in POCT sensitivity, the proportion of patients getting treated immediately, the baseline proportion lost to follow-up (LTFU), and the average treatment delay. RESULTS: In Analysis 1, high POCT sensitivity was needed to reduce the chlamydia-associated burden. With a POCT sensitivity of 90%, reductions from the baseline burden only occurred in scenarios in which over 60% of the screened individuals would get immediate treatment and the baseline LTFU proportion was 20%. With a POCT sensitivity of 99% (baseline LTFU 10%, 2-week treatment delay), if everyone were treated immediately, the prevalence reduction was estimated at 5.7% (95% credible interval [CrI] 3.9-8.2%). If only 30% of tested persons would wait for results, the prevalence reduction was only 1.6% (95% CrI 1.1-2.3). POCT with 99% sensitivity could avert up to 12 700 (95% CrI 5000-22 200) PID cases per year, if 100% were treated immediately (baseline LTFU 20% and 3-week treatment delay). In Analysis 2, when POCT was coupled with increasing screening coverage, reductions in the chlamydia burden could be realized with a POCT sensitivity of 90%. CONCLUSIONS: POCT could improve chlamydia prevention efforts if test performance characteristics are significantly improved over currently available options.

Exploring How Epidemic Context Influences Syphilis Screening Impact: A Mathematical Modeling Study.

BACKGROUND: The current syphilis epidemic in the United States is concentrated in gay, bisexual, and other men who have sex with men (MSM), but substantial heterosexual transmission is reported in some parts of the country. Using the US states of Louisiana and Massachusetts as case studies, we investigated how epidemic context influences the impact of population screening approaches for syphilis control. METHODS: We constructed a compartmental metapopulation model parameterized to describe observed patterns of syphilis transmission. We estimated the impact of different approaches to screening, including perfect adherence to current US screening guidelines in MSM. RESULTS: In Louisiana, where syphilis cases are more evenly distributed among MSM and heterosexual populations, we projected that screening according to guidelines would contribute to no change or an increase in syphilis burden, compared with burden with current estimated screening coverage. In Massachusetts, which has a more MSM-focused outbreak, we projected that screening according to guidelines would be as or more effective than current screening coverage in most population groups. CONCLUSIONS: Men who have sex with men-focused approaches to screening may be insufficient for control when there is substantial transmission in heterosexual populations. Epidemic characteristics may be useful when identifying at-risk groups for syphilis screening.

Population-level Benefits of Extragenital Gonorrhea Screening Among Men Who Have Sex With Men: An Exploratory Modeling Analysis.

BACKGROUND: Men who have sex with men (MSM) are disproportionately burdened by gonorrhea and face high rates of extragenital (rectal and pharyngeal) infection, which is mostly asymptomatic and often missed by urogenital-only screening. Extragenital screening likely remains below Centers for Disease Control and Prevention-recommended levels. Because increasing screening coverage is often resource-intensive, we assessed whether improved extragenital screening among men already presenting at clinics could lead to substantial reductions in prevalence and incidence. METHODS: We calibrated an agent-based model of site- and race-specific gonorrhea infection in MSM to explicitly model multisite infection within an individual and transmission via anal, orogenital, and ororectal sex. Compared with current screening levels, we assessed the impact of increasing screening at (1) both extragenital sites, (2) only the rectal site, and (3) only the pharyngeal site among men already being urogenitally screened. RESULTS: All scenarios reduced prevalence and incidence, with improved screening at both extragenital sites having the largest effect across outcomes. Extragenitally screening 100% of men being urogenitally screened reduced site-specific prevalence by an average of 42% (black MSM) and 50% (white MSM), with these values dropping by approximately 10% and 20% for each race group when targeting only the rectum and only the pharynx, respectively. However, increasing only rectal screening was more efficient in terms of the number of screens needed to avert an infection as this avoided duplicative screens due to rectum/pharynx multisite infection. CONCLUSIONS: Improved extragenital screening substantially reduced site-specific gonorrhea prevalence and incidence, with strategies aimed at increasing rectal screening proving the most efficient.

The Potential Population-Level Impact of Different Gonorrhea Screening Strategies in Baltimore and San Francisco: An Exploratory Mathematical Modeling Analysis.

BACKGROUND: Baltimore and San Francisco represent high burden areas for gonorrhea in the United States. We explored different gonorrhea screening strategies and their comparative impact in the 2 cities. METHODS: We used a compartmental transmission model of gonorrhea stratified by sex, sexual orientation, age, and race/ethnicity, calibrated to city-level surveillance data for 2010 to 2017. We analyzed the benefits of 5-year interventions which improved retention in care cascade or increased screening from current levels. We also examined a 1-year outreach screening intervention of high-activity populations. RESULTS: In Baltimore, annual screening of population aged 15 to 24 years was the most efficient of the 5-year interventions with 17.9 additional screening tests (95% credible interval [CrI], 11.8-31.4) needed per infection averted while twice annual screening of the same population averted the most infections (5.4%; 95% CrI, 3.1-8.2%) overall with 25.3 (95% CrI, 19.4-33.4) tests per infection averted. In San Francisco, quarter-annual screening of all men who have sex with men was the most efficient with 16.2 additional (95% CrI, 12.5-44.5) tests needed per infection averted, and it also averted the most infections (10.8%; 95% CrI, 1.2-17.8%). Interventions that reduce loss to follow-up after diagnosis improved outcomes. Depending on the ability of a short-term outreach screening to screen populations at higher acquisition risk, such interventions can offer efficient ways to expand screening coverage. CONCLUSIONS: Data on gonorrhea prevalence distribution and time trends locally would improve the analyses. More focused intervention strategies could increase the impact and efficiency of screening interventions.

Mathematical modeling study of school-based chlamydia screening: potential impact on chlamydia prevalence in intervention schools and surrounding communities.

BACKGROUND: Chlamydia screening in high schools offers a way to reach adolescents outside of a traditional clinic setting. Using transmission dynamic modeling, we examined the potential impact of high-school-based chlamydia screening programs on the burden of infection within intervention schools and surrounding communities, under varying epidemiological and programmatic conditions. METHODS: A chlamydia transmission model was calibrated to epidemiological data from three different settings. Philadelphia and Chicago are two high-burden cities with existing school-based screening programs. Rural Iowa does not have an existing program but represents a low-burden setting. We modeled the effects of the two existing programs to analyze the potential influence of program coverage and student participation. All three settings were used to examine a broader set of hypothetical programs with varying coverage levels and time trends in participation. RESULTS: In the modeled Philadelphia program, prevalence among the intervention schools' sexually active 15-18 years old population was 4.34% (95% credible interval 3.75-4.71%)after 12 program years compared to 5.03% (4.39-5.43%) in absence of the program. In the modeled Chicago program, prevalence was estimated as 5.97% (2.60-7.88%) after 4 program years compared to 7.00% (3.08-9.29%) without the program. In the broader hypothetical scenarios including both high-burden and low-burden settings, impact of school-based screening programs was greater in absolute terms in the higher-prevalence settings, and benefits in the community were approximately proportional to population coverage of intervention schools. Most benefits were garnered if the student participation did not decline over time. CONCLUSIONS: Sustained high student participation in school-based screening programs and broad coverage of schools within a target community are likely needed to maximize program benefits in terms of reduced burden of chlamydia in the adolescent population.

Estimated costs and quality-adjusted life-years lost due to N. gonorrhoeae infections acquired in 2015 in the United States: A modelling study of overall burden and disparities by age, race/ethnicity, and other factors.

Background: Disparities in the health and economic burden of gonorrhoea have not been systematically quantified. We estimated population-level health losses and costs associated with gonococcal infection and sequelae in the United States. Methods: We used probability-tree models to capture gonorrhoea sequelae and to estimate attributable disease burden in terms of the discounted lifetime costs and quality-adjusted life-years (QALYs) lost due to incident infections acquired during 2015 from the healthcare system perspective. Numbers of infections in 2015 were obtained from a published gonorrhoea transmission model. We evaluated population-level disease burden, disaggregated by sex, age, race/ethnicity, and for men who have sex with men (MSM). We conducted a multivariate sensitivity analysis for key parameters. Findings: Discounted lifetime QALYs lost per incident gonococcal infection were estimated as 0.093 (95% uncertainty interval [UI] 0.022-0.22) for women, 0.0020 (0.0015-0.0024) for heterosexual men, and 0.0015 (0.00070-0.0021) for MSM. Discounted lifetime costs per incident infection were USD 261 (109-480), 169 (88-263), and 133 (50-239), respectively. At the population level, total discounted lifetime QALYs lost due to infections acquired during 2015 were 53,293 (12,326-125,366) for women, 621 (430-872) for heterosexual men, and 1,078 (427-1,870) for MSM. Total discounted lifetime costs were USD 150 million (64-277 million), 54 million (25-92 million), and 97 million (34-197 million), respectively. The highest total burden of both QALYs and costs at the population-level was observed in Non-Hispanic Black women, and highest burden per 1,000 person-years was identified in MSM among men and American Indian/Alaska Native among women. Interpretation: Gonorrhoea causes substantial health losses and costs in the United States. These results can inform planning and prioritization of prevention services. Funding: Centers for Disease Control and Prevention, Charles A. King Trust.

A review of network simulation models of hepatitis C virus and HIV among people who inject drugs.

Network modelling is a valuable tool for simulating hepatitis C virus (HCV) and HIV transmission among people who inject drugs (PWID) and assessing the potential impact of treatment and harm-reduction interventions. In this paper, we review literature on network simulation models, highlighting key structural considerations and questions that network models are well suited to address. We describe five approaches (Erdös-Rényi, Stochastic Block, Watts-Strogatz, Barabási-Albert, and Exponential Random Graph Model) used to model partnership formation with emphasis on the strengths of each approach in simulating different features of real-world PWID networks. We also review two important structural considerations when designing or interpreting results from a network simulation study: (1) dynamic vs. static network and (2) injection only vs. both injection and sexual networks. Dynamic network simulations allow partnerships to evolve and disintegrate over time, capturing corresponding shifts in individual and population-level risk behaviour; however, their high level of complexity and reliance on difficult-to-observe data has driven others to develop static network models. Incorporating both sexual and injection partnerships increases model complexity and data demands, but more accurately represents HIV transmission between PWID and their sexual partners who may not also use drugs. Network models add the greatest value when used to investigate how leveraging network structure can maximize the effectiveness of health interventions and optimize investments. For example, network models have shown that features of a given network and epidemic influence whether the greatest community benefit would be achieved by allocating hepatitis C or HIV treatment randomly, versus to those with the most partners. They have also demonstrated the potential for syringe services and "buddy sharing" programs to reduce disease transmission.

Family Identification of Delirium in the Emergency Department in Patients With and Without Dementia: Validity of the Family Confusion Assessment Method (FAM-CAM).

OBJECTIVE: To examine the ability of the family-rated Family Confusion Assessment Method (FAM-CAM) to identify delirium in the emergency department (ED) among patients with and without dementia, as compared to the reference-standard Confusion Assessment Method (CAM). DESIGN: Validation study. SETTING: Urban academic ED. PARTICIPANTS: Dyads of ED patients, aged 70 years and older, and their family caregivers (N = 108 dyads). MEASUREMENTS: A trained reference standard interviewer performed a cognitive screen, delirium symptom assessment, and scored the CAM. The caregiver self-administered the FAM-CAM. Dementia was assessed using the Informant Questionnaire on Cognitive Decline in the Elderly and the medical record. For concurrent validity, performance of the FAM-CAM was compared to the CAM. For predictive validity, clinical outcomes (ED visits, hospitalization, and mortality) over 6 months were compared in FAM-CAM positive and negative patients, controlling for age, sex, comorbidity, and cognitive status. RESULTS: Among the 108 patients, 30 (28%) were CAM positive for delirium and 58 (54%) presented with dementia. The FAM-CAM had a specificity of 83% and a negative predictive value of 83%. Most false negatives (n = 9 of 13, 69%) were due to caregivers not identifying the inattention criteria for delirium on the FAM-CAM. In patients with dementia, sensitivity was higher than in patients without (61% vs 43%). In adjusted models, a hospitalization in the following 6 months was more than three times as likely in FAM-CAM positive compared to negative patients (odds ratio = 3.4; 95% confidence interval = 1.2-9.3). CONCLUSIONS: Among patients with and without dementia, the FAM-CAM shows qualities that are important in the ED setting for identification of delirium. Using the FAM-CAM as part of a systematic screening strategy for the ED, in which families' assessments could supplement healthcare professionals' assessments, is promising. J Am Geriatr Soc 68:983-990, 2020.

Using support vector machines on photoplethysmographic signals to discriminate between hypovolemia and euvolemia.

Identifying trauma patients at risk of imminent hemorrhagic shock is a challenging task in intraoperative and battlefield settings given the variability of traditional vital signs, such as heart rate and blood pressure, and their inability to detect blood loss at an early stage. To this end, we acquired N = 58 photoplethysmographic (PPG) recordings from both trauma patients with suspected hemorrhage admitted to the hospital, and healthy volunteers subjected to blood withdrawal of 0.9 L. We propose four features to characterize each recording: goodness of fit (r2), the slope of the trend line, percentage change, and the absolute change between amplitude estimates in the heart rate frequency range at the first and last time points. Also, we propose a machine learning algorithm to distinguish between blood loss and no blood loss. The optimal overall accuracy of discriminating between hypovolemia and euvolemia was 88.38%, while sensitivity and specificity were 88.86% and 87.90%, respectively. In addition, the proposed features and algorithm performed well even when moderate blood volume was withdrawn. The results suggest that the proposed features and algorithm are suitable for the automatic discrimination between hypovolemia and euvolemia, and can be beneficial and applicable in both intraoperative/emergency and combat casualty care.