Comparison of emergency medical services and emergency department encounter trends for nonfatal opioid-involved overdoses, nine states, United States, 2020-2022.

BACKGROUND: Opioid-involved overdoses, especially those involving synthetic opioids like fentanyl, have driven increases in overdose morbidity and mortality. Emergency medical services (EMS) and emergency department (ED) data can each provide near real-time information on trends in nonfatal opioid-involved overdoses; however, minimal data exist on the comparability of trends in these two data sources. METHODS: EMS data from biospatial© and ED data from CDC's Drug Overdose Surveillance and Epidemiology system and National Syndromic Surveillance Program were queried for nine states. Counts of total encounters, opioid-involved overdose encounters, and rates of opioid-involved overdoses per 10,000 total encounters were calculated for each data source from 2020-2022. Trends in monthly counts and rates were assessed using Joinpoint regression. RESULTS: On average, EMS data captured 1.8 times more monthly opioid-involved overdose encounters than ED data. Trends in the counts of opioid-involved overdose encounters were similar in both data sources with increases and decreases occurring during roughly the same periods. Overall, trends in rates of opioid-involved overdose encounters were also comparable. CONCLUSIONS: EMS and ED data provide complementary information for understanding overdose trends. Study findings underscore the importance of implementing post-overdose response protocols by both EMS and ED providers to ensure patient receive services irrespective of care setting.

High School Follow-Up of the Dating Matters® RCT: Effects on Teen Dating Violence and Relationship Behaviors.

Teen dating violence (TDV) is a significant public health problem that can have lifelong consequences. Using a longitudinal, cluster randomized controlled trial (RCT), this study examines whether the Dating Matters comprehensive prevention model, implemented in middle school, prevented TDV and negative relationship behaviors and promoted positive relationship behaviors in high school (9th-11th grades), when compared with a standard of care intervention. Dating Matters includes programs for sixth to eighth grade youth and their parents, training for school staff, a youth communications program, and policy and data activities implemented in the community. Self-report survey data were collected from students in 46 middle schools that were randomly assigned to condition within site. Students completed two surveys (fall and spring) in each middle school grade and a single survey in the spring of each high school grade. This study examined self-reported TDV perpetration and victimization, use of negative conflict resolution strategies, and positive relationship skills in the high school follow-up. While varying patterns emerged, latent panel models demonstrated significant program effects for all outcomes. Dating Matters students reported 19% reduced risk for TDV perpetration, 24% reduced risk for TDV victimization, 7% reduced risk for use of negative conflict strategies, and 3% more use of positive relationship skills, on average across time and cohort, than standard of care students. On average, Dating Matters, implemented in middle school, continued to be more effective at reducing TDV perpetration, TDV victimization, and use of negative conflict resolution strategies in high school than an evidence-based comparison program.Trial Registration: clinicaltrials.gov Identifier: NCT01672541.

Estimating the ratio of fatal to non-fatal overdoses involving all drugs, all opioids, synthetic opioids, heroin or stimulants, USA, 2010-2020.

INTRODUCTION: US drug overdose deaths are at historic levels. For every fatal drug overdose, there are many more non-fatal; however, minimal nationally representative data exist on trends in the ratio of fatal to non-fatal drug overdoses and how this differs by drug type. METHODS: Data from the Centers for Disease Control and Prevention's National Vital Statistics System were used to assess the number of fatal overdoses; data from the Healthcare Cost and Utilization Project Nationwide Emergency Department Sample database were used to estimate the number of non-fatal overdoses treated in emergency departments. Counts of fatal and non-fatal overdoses by drug type (all drug, all opioid, synthetic opioid, heroin, stimulant, and opioid and stimulant polysubstance) were calculated from 2010 to 2020 (for non-fatal synthetic opioid-involved overdoses, from 2016 to 2020 only). Trends in overdose counts and the ratio of fatal to non-fatal overdoses were assessed. RESULTS: On average, counts of fatal overdoses increased quarterly among all drug types, and non-fatal overdoses increased among most drug types. Over the 11-year period, the greatest average quarterly percent change (AQPC) in fatal overdose counts was among synthetic opioid-involved overdoses (AQPC: 7.1%; 95% CI: 6.0 to 8.2) and for non-fatal overdoses was among heroin-involved overdoses (AQPC: 4.3%; 95% CI: 3.9 to 4.8). During 2010‒2020, there was approximately 1 fatal overdose per 15 non-fatal. The ratio of fatal to non-fatal drug overdoses increased among every drug type except heroin; ratio increases were driven by greater relative increases in fatal overdoses compared with non-fatal. CONCLUSIONS: Assessment of the ratio of fatal to non-fatal drug overdoses can be used to understand the lethality of different drugs and inform response and prevention efforts.

Cannabis-Involved Emergency Department Visits Among Persons Aged <25 Years Before and During the COVID-19 Pandemic - United States, 2019-2022.

To understand trends in U.S. cannabis-involved emergency department (ED) visits (i.e., those for which cannabis use was documented in the chief complaint or a discharge diagnosis) among young persons aged <25 years during the COVID-19 pandemic, CDC used National Syndromic Surveillance Program data to examine changes in ED visits during 2019-2022. Mean weekly cannabis-involved ED visits among all young persons were higher during the COVID-19 pandemic in 2020, 2021, and 2022, compared with corresponding periods in 2019. Large increases in cannabis-involved ED visits throughout the COVID-19 pandemic compared with prepandemic surveillance periods in 2019 were identified among persons aged ≤10 years. ED visit rates among children and adolescents aged 11-14 years did not differ by sex until the first half of the 2020-21 school year (2020, weeks 37-53), when ED visit rates among females surpassed those among males. Improving clinicians' awareness of rising cannabis-involved ED visits might aid in early diagnosis of cannabis intoxication among young persons. Further, increasing adults' knowledge regarding safe cannabis storage practices, strengthening youths' coping and problem-solving skills through evidence-based prevention programs, and modifying cannabis packaging to decrease appeal to youths might help prevent intentional and unintentional cannabis use.

Emergency Department Visits Involving Mental Health Conditions, Suicide-Related Behaviors, and Drug Overdoses Among Adolescents - United States, January 2019-February 2023.

The U.S. adolescent mental and behavioral health crisis is ongoing,* with high pre-COVID-19 pandemic baseline rates† (1) and further increases in poor mental health (2), suicide-related behaviors (3), and drug overdose deaths (4) reported during 2020-2021. CDC examined changes in U.S. emergency department (ED) visits for mental health conditions (MHCs) overall and for nine specific MHCs,§ suicide-related behaviors (including suspected suicide attempts), and drug-involved overdoses (including opioids) among children and adolescents aged 12-17 years (adolescents) during January 2019-February 2023, overall and by sex. Compared with fall 2021, by fall 2022, decreases in weekly ED visits were reported among all adolescents, and females specifically, for MHCs overall, suicide-related behaviors, and drug overdoses; weekly ED visits among males were stable. During this same period, increases in weekly ED visits for opioid-involved overdoses were detected. Mean weekly ED visits in fall 2022 for suicide-related behaviors and MHCs overall were at or lower than the 2019 prepandemic baseline, respectively, and drug overdose visits were higher. Differences by sex were observed; levels among females were at or higher than prepandemic baselines for these conditions. These findings suggest some improvements as of fall 2022 in the trajectory of adolescent mental and behavioral health, as measured by ED visits; however, poor mental and behavioral health remains a substantial public health problem, particularly among adolescent females. Early identification and trauma-informed interventions, coupled with expanded evidence-based, comprehensive prevention efforts, are needed to support adolescents' mental and behavioral health.

Characterization of Nonfatal Opioid, Cocaine, Methamphetamine, and Polydrug Exposure and Clinical Presentations Reported to the Toxicology Investigators Consortium Core Registry, January 2010-December 2021.

INTRODUCTION: To characterize and compare opioid-only, cocaine-only, methamphetamine-only, opioid-and-cocaine exposure, and opioid-and-methamphetamine exposure and to examine clinical presentations, leading to a better understanding of overdose effects involving these drug exposures. METHODS: We examined drug exposures in the Toxicology Investigators Consortium (ToxIC) Core Registry from January 2010 to December 2021, a case registry of patients presenting to participating healthcare sites that receive a medical toxicology consultation. Demographic and clinical presentations of opioid-only, cocaine-only, methamphetamine-only, and opioid-and-cocaine exposure, and opioid-and-methamphetamine exposure consultations were described; differences between single and polydrug exposure subgroups were calculated to determine statistical significance. Clinical presentations associated with exposures were evaluated through calculated adjusted relative risk. RESULTS: A total of 3,883 consultations involved opioids, cocaine, methamphetamine, opioid-and-cocaine exposure, or opioid-and-methamphetamine exposure. Opioid-only (n = 2,268, 58.4%) and methamphetamine-only (n = 712, 18.3%) comprised most consultations. There were significant differences in clinical presentations between exposure subgroups. Opioid-and-cocaine exposure consultations were 8.15 times as likely to present with a sympathomimetic toxidrome than opioid-only. Conversely, opioid-and-cocaine exposure and opioid-and-methamphetamine exposure were 0.32 and 0.42 times as likely to present with a sympathomimetic toxidrome compared to cocaine-only and methamphetamine-only consultations, respectively. Opioid-and-cocaine exposure was 0.67 and opioid-and-methamphetamine exposure was 0.74 times as likely to present with respiratory depression compared to opioid-only consultations. Similarly, opioid-and-cocaine exposure was 0.71 and opioid-and-methamphetamine exposure was 0.78 times as likely to present with CNS depression compared to opioid-only consultations. CONCLUSIONS: Used in combination, opioids and stimulants may mask typical clinical presentations of one another, misattributing incorrect drugs to overdose in both clinical treatment and public health surveillance.

Analysis of trends and usage of ICD-10-CM discharge diagnosis codes for poisonings by fentanyl, tramadol, and other synthetic narcotics in emergency department data.

Synthetic opioids, including illicitly manufactured fentanyls, are driving recent increases in US overdose deaths. Beginning October 2020, the International Classification of Diseases, 10th revision, Clinical Modification (ICD-10-CM) code for poisonings involving synthetic narcotics (T40.4X) was split into three codes: fentanyl (T40.41), tramadol (T40.42), and other synthetic narcotics (T40.49). Emergency department data from October 2019-September 2021 in the Centers for Disease Control and Prevention's National Syndromic Surveillance Program BioSense platform were queried for synthetic opioid codes in the chief complaint and discharge diagnosis fields. Trend analyses assessed average monthly percent change overall and by sex and age. Emergency department visits for overdoses involving synthetic narcotics increased on average 3.2 % each month before the code split and 4.8 % after. Visits with fentanyl codes drove this increase after the split, accounting for most visits among males, females, and every age group except ≥ 65 years. The average monthly percent increase for ED visits for fentanyl-involved overdoses was greater than for all synthetic narcotics combined (i.e., T40.41, T40.42, and/or T40.49), suggesting that the old code (T40.4X) masked the full extent of the increase in ED visits for fentanyl overdoses. Usage of these new codes can improve tracking of non-fatal synthetic opioid overdose trends.

Patient-Level and County-Level Trends in Nonfatal Opioid-Involved Overdose Emergency Medical Services Encounters - 491 Counties, United States, January 2018-March 2022.

The number of nonfatal opioid-involved overdoses treated by health care providers has risen in the United States; the median number of emergency department (ED) visits for these overdoses was significantly higher during 2020 than during 2019 (1). ED visit data can underestimate nonfatal opioid-involved overdose incidence because, increasingly, persons experiencing a nonfatal opioid overdose are refusing transport to EDs by emergency medical services (EMS) (2). A study in Kentucky found that during a 6-month period, 19.8% of persons treated by EMS for an opioid overdose refused transport to an ED (2). Thus, EMS encounter data involving suspected nonfatal opioid-involved overdoses complement ED data and also allow for near real-time analysis (3). This report describes trends in rates of EMS encounters for nonfatal opioid-involved overdoses per 10,000 total EMS encounters (rates) by selected patient- and county-level characteristics during January 2018­March 2022 in 491 counties from 21 states using data from biospatial, Inc.* During this period, the nonfatal opioid-involved overdose rate increased, on average, 4.0% quarterly. Rates increased for both sexes and for most age groups. Rates were highest among non-Hispanic White (White) and non-Hispanic Native Hawaiian or other Pacific Islander (NH/OPI) persons, and increases were largest among non-Hispanic Black (Black), followed by Hispanic or Latino (Hispanic) persons. Rates increased in both urban and rural counties and for all quartiles of county-level characteristics (i.e., unemployment, education, and uninsured), except in counties with the lowest percentage of uninsured persons. Rates were highest and rate increases were largest in urban counties and counties with higher unemployment rates. This analysis of nonfatal opioid-involved overdose trends in EMS data highlights the utility of these data and the importance of addressing inequities that contribute to disproportionate overdose risk, such as through focused outreach to racial and ethnic minority groups, who disproportionately experience these inequities, and communities with higher levels of unemployment. EMS providers are in a unique position to engage in postoverdose response protocols and promote evidence-based overdose education and facilitate linkage to care and harm reduction services.†,§

Estimating Weekly National Opioid Overdose Deaths in Near Real Time Using Multiple Proxy Data Sources.

Importance: Opioid overdose is a leading public health problem in the United States; however, national data on overdose deaths are delayed by several months or more. Objectives: To build and validate a statistical model for estimating national opioid overdose deaths in near real time. Design, Setting, and Participants: In this cross-sectional study, signals from 5 overdose-related, proxy data sources encompassing health, law enforcement, and online data from 2014 to 2019 in the US were combined using a LASSO (least absolute shrinkage and selection operator) regression model, and weekly predictions of opioid overdose deaths were made for 2018 and 2019 to validate model performance. Results were also compared with those from a baseline SARIMA (seasonal autoregressive integrated moving average) model, one of the most used approaches to forecasting injury mortality. Exposures: Time series data from 2014 to 2019 on emergency department visits for opioid overdose from the National Syndromic Surveillance Program, data on the volume of heroin and synthetic opioids circulating in illicit markets via the National Forensic Laboratory Information System, data on the search volume for heroin and synthetic opioids on Google, and data on post volume on heroin and synthetic opioids on Twitter and Reddit were used to train and validate prediction models of opioid overdose deaths. Main Outcomes and Measures: Model-based predictions of weekly opioid overdose deaths in the United States were made for 2018 and 2019 and compared with actual observed opioid overdose deaths from the National Vital Statistics System. Results: Statistical models using the 5 real-time proxy data sources estimated the national opioid overdose death rate for 2018 and 2019 with an error of 1.01% and -1.05%, respectively. When considering the accuracy of weekly predictions, the machine learning-based approach possessed a mean error in its weekly estimates (root mean squared error) of 60.3 overdose deaths for 2018 (compared with 310.2 overdose deaths for the SARIMA model) and 67.2 overdose deaths for 2019 (compared with 83.3 overdose deaths for the SARIMA model). Conclusions and Relevance: Results of this serial cross-sectional study suggest that proxy administrative data sources can be used to estimate national opioid overdose mortality trends to provide a more timely understanding of this public health problem.

Trends and characteristics of cannabis-associated emergency department visits in the United States, 2006-2018.

BACKGROUND: Cannabis policies are rapidly changing in the United States, yet little is known about how this has affected cannabis-associated emergency department (ED) visits. METHODS: We studied trends in cannabis-associated ED visits and identified differences by visit characteristics. Cannabis-associated ED visits from 2006 to 2018 were identified from the Agency for Healthcare Research and Quality's Healthcare Cost and Utilization Project's (HCUP) Nationwide Emergency Department Sample (NEDS). JoinPoint analysis was used to identify trends from 2006 to 2014, prior to medical coding changes in 2015, and Z-tests were used to compare annual rate changes from 2016 to 2018. Changes in rates from 2017 to 2018 were examined by visit characteristics. RESULTS: From 2006-2014, the rate of cannabis-associated ED visits increased, on average, 12.1% annually (p < 0.05), from 12.3 to 34.7 visits per 100,000 population. The rate increased 17.3% from 2016 to 2017 (p < 0.05) and 11.1% from 2017 to 2018 (p < 0.05). From 2017-2018, rates of visits increased for both males (8.7%; p < 0.05) and females (15.9%; p < 0.05). Patients 0-14 years and 25 years and older had significant rate increases from 2017 to 2018 as did the Midwest region (36.8%; p < 0.05), the Northeast (9.2%; p < 0.05), and the South (4.5%; p < 0.05). CONCLUSIONS: Cannabis-associated ED visits are on the rise and subgroups are at increased risk. Some potential explanations for increases in cannabis-associated ED visits include increased availability of cannabis products, increased use, and diversity of products available in marketplaces. Strategies are needed to prevent youth initiation, limit potentially harmful use among adults, and ensure safe storage where cannabis use is legal.

Methamphetamine use in the United States: epidemiological update and implications for prevention, treatment, and harm reduction.

Recent attention has focused on the growing role of psychostimulants, such as methamphetamine in overdose deaths. Methamphetamine is an addictive and potent stimulant, and its use is associated with a range of physical and mental health harms, overdose, and mortality. Adding to the complexity of this resurgent methamphetamine threat is the reality that the increases in methamphetamine availability and harms are occurring in the midst of and intertwined with the ongoing opioid overdose crisis. Opioid involvement in psychostimulant-involved overdose deaths increased from 34.5% of overdose deaths in 2010 to 53.5% in 2019-an increase of more than 50%. This latest evolution of the nation's overdose epidemic poses novel challenges for prevention, treatment, and harm reduction. This narrative review synthesizes what is known about changing patterns of methamphetamine use with and without opioids in the United States, other characteristics associated with methamphetamine use, the contributions of the changing illicit drug supply to use patterns and overdose risk, motivations for couse of methamphetamine and opioids, and awareness of exposure to opioids via the illicit methamphetamine supply. Finally, the review summarizes illustrative community and health system strategies and research opportunities to advance prevention, treatment, and harm reduction policies, programs, and practices.

A descriptive exploration of the geographic and sociodemographic concentration of firearm homicide in the United States, 2004-2018.

This study examined the population-based incidence of firearm homicide in the United States to identify geographic concentrations and to determine whether such concentrations have changed over time. It further examined the simultaneous associations of urbanization, poverty, and ethnicity/race with firearm homicide incidence. Using county-level data from the National Vital Statistics System and the U.S. Census Bureau for the years 2004-2018, the findings show geographic patterns not commonly recognized, including several lengthy and continuous corridors with a high incidence of firearm homicide, traversing both metro and non-metro areas. While the data clearly show a strongly disproportionate concentration of firearm homicide incidence in a subset of the population defined by geography, they do not suggest increasing concentration over time. The study findings also generally indicate increasing firearm homicide incidence with increasing levels of surrounding poverty, a phenomenon observed for both metro and non-metro areas.

Differences and similarities between emergency department syndromic surveillance and hospital discharge data for nonfatal drug overdose.

PURPOSE: Emergency department syndromic surveillance and hospital discharge data have been used to detect and monitor nonfatal drug overdose, yet few studies have assessed the differences and similarities between these two data sources. METHODS: The Centers for Disease Control and Prevention Drug Overdose Surveillance and Epidemiology system data from 14 states were used to compare these two sources at estimating monthly overdose burden and trends from January 2018 through December 2019 for nonfatal all drug, opioid-, heroin-, and stimulant-involved overdoses. RESULTS: Compared to discharge data, syndromic data captured 13.3% more overall emergency department visits, 67.8% more all drug overdose visits, 15.6% more opioid-involved overdose visits, and 78.8% more stimulant-involved overdose visits. Discharge data captured 18.9% more heroin-involved overdoses. Significant trends were identified for all drug (Average Monthly Percentage Change [AMPC]=1.1, 95% CI=0.4,1.8) and stimulant-involved overdoses (AMPC=2.4, 95% CI=1.2,3.7) in syndromic data; opioid-involved overdoses increased in both discharge and syndromic data (AMPCDischarge=0.9, 95% CI=0.2,1.7; AMPCSyndromic=1.9, CI=1.1,2.8). CONCLUSIONS: Results demonstrate that discharge data may be better for reporting counts, yet syndromic data are preferable to detect changes quickly and to alert practitioners and public health officials to local overdose clusters. These data sources do serve complementary purposes when examining overdose trends.

Defining indicators for drug overdose emergency department visits and hospitalisations in ICD-10-CM coded discharge data.

INTRODUCTION: The drug overdose epidemic has worsened over the past decade; however, efforts have been made to better understand and track nonfatal overdoses using various data sources including emergency department and hospital admission data from billing and discharge files. METHODS AND FINDINGS: The Centers for Disease Control and Prevention (CDC) has developed surveillance case definition guidance using standardised discharge diagnosis codes for public health practitioners and epidemiologists using lessons learnt from CDC's funded recipients and the Council for State and Territorial Epidemiologists (CSTE) International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) Drug Poisoning Indicators Workgroup and General Injury ICD-10-CM Workgroup. CDC's guidance was informed by health departments and CSTE's workgroups and included several key aspects for assessing drug overdose in emergency department and hospitalisation discharge data. These include: (1) searching all diagnosis fields to identify drug overdose cases; (2) estimating drug overdose incidence using visits for initial encounter but excluding subsequent encounters and sequelae; (3) excluding underdosing and adverse effects from drug overdose incidence indicators; and (4) using codes T36-T50 for overdose surveillance. CDC's guidance also suggests analysing intent separately for ICD-10-CM coding. CONCLUSIONS: CDC's guidance provides health departments a key tool to better monitor drug overdoses in their community. The implementation and validation of this standardised guidance across all CDC-funded health departments will be key to ensuring consistent and accurate reporting across all entities.

Trends in US Emergency Department Visits for Mental Health, Overdose, and Violence Outcomes Before and During the COVID-19 Pandemic.

Importance: The coronavirus disease 2019 (COVID-19) pandemic, associated mitigation measures, and social and economic impacts may affect mental health, suicidal behavior, substance use, and violence. Objective: To examine changes in US emergency department (ED) visits for mental health conditions (MHCs), suicide attempts (SAs), overdose (OD), and violence outcomes during the COVID-19 pandemic. Design, Setting, and Participants: This cross-sectional study used data from the Centers for Disease Control and Prevention's National Syndromic Surveillance Program to examine national changes in ED visits for MHCs, SAs, ODs, and violence from December 30, 2018, to October 10, 2020 (before and during the COVID-19 pandemic). The National Syndromic Surveillance Program captures approximately 70% of US ED visits from more than 3500 EDs that cover 48 states and Washington, DC. Main Outcomes and Measures: Outcome measures were MHCs, SAs, all drug ODs, opioid ODs, intimate partner violence (IPV), and suspected child abuse and neglect (SCAN) ED visit counts and rates. Weekly ED visit counts and rates were computed overall and stratified by sex. Results: From December 30, 2018, to October 10, 2020, a total of 187 508 065 total ED visits (53.6% female and 46.1% male) were captured; 6 018 318 included at least 1 study outcome (visits not mutually exclusive). Total ED visit volume decreased after COVID-19 mitigation measures were implemented in the US beginning on March 16, 2020. Weekly ED visit counts for all 6 outcomes decreased between March 8 and 28, 2020 (March 8: MHCs = 42 903, SAs = 5212, all ODs = 14 543, opioid ODs = 4752, IPV = 444, and SCAN = 1090; March 28: MHCs = 17 574, SAs = 4241, all ODs = 12 399, opioid ODs = 4306, IPV = 347, and SCAN = 487). Conversely, ED visit rates increased beginning the week of March 22 to 28, 2020. When the median ED visit counts between March 15 and October 10, 2020, were compared with the same period in 2019, the 2020 counts were significantly higher for SAs (n = 4940 vs 4656, P = .02), all ODs (n = 15 604 vs 13 371, P < .001), and opioid ODs (n = 5502 vs 4168, P < .001); counts were significantly lower for IPV ED visits (n = 442 vs 484, P < .001) and SCAN ED visits (n = 884 vs 1038, P < .001). Median rates during the same period were significantly higher in 2020 compared with 2019 for all outcomes except IPV. Conclusions and Relevance: These findings suggest that ED care seeking shifts during a pandemic, underscoring the need to integrate mental health, substance use, and violence screening and prevention services into response activities during public health crises.

Development and Validation of a Syndrome Definition to Identify Suspected Nonfatal Heroin-Involved Overdoses Treated in Emergency Departments.

CONTEXT: The Centers for Disease Control and Prevention (CDC) works closely with states and local jurisdictions that are leveraging data from syndromic surveillance systems to identify meaningful changes in overdose trends. CDC developed a suspected nonfatal heroin overdose syndrome definition for use with emergency department (ED) data to help monitor trends at the national, state, and local levels. OBJECTIVE: This study assesses the percentage of true-positive unintentional and undetermined intent heroin-involved overdose (UUHOD) captured by this definition. DESIGN/SETTING: CDC applied the UUHOD definition to ED data available in CDC's National Syndromic Surveillance Program (NSSP). Data were analyzed from 18 states that shared access to their syndromic data in NSSP with the CDC overdose morbidity team. Data were analyzed using queries and manual reviews to identify heroin overdose diagnosis codes and text describing chief complaint reasons for ED visits. MEASURES: The percentage of true-positive UUHOD was calculated as the number of true-positives divided by the number of total visits captured by the syndrome definition. RESULTS: In total, 99 617 heroin overdose visits were identified by the syndrome definition. Among 95 323 visits identified as acute heroin-involved overdoses, based on reviews of chief complaint text and diagnosis codes, 967 (1.0%) were classified as possible intentional drug overdoses. Among all 99 617 visits, 94 356 (94.7%) were classified as true-positive UUHOD; 2226 (2.2%) and 3035 (3.0%) were classified as "no" and "maybe" UUHOD, respectively. CONCLUSION: Analysis of the CDC heroin overdose syndrome definition determined that nearly all visits were captured accurately for patients presenting to the ED for a suspected acute UUHOD. This definition will continue to be valuable for ongoing heroin overdose surveillance and epidemiologic analysis of heroin overdose patterns. CDC will evaluate possible definition refinements as new products and terms for heroin overdose emerge.