Ambulatory Care Monthly News

Important Announcement

The National Center for Health Statistics (NCHS) would like to announce that the National Hospital Ambulatory Medical Care Survey (NHAMCS) will cease after the collection and processing of the 2022 annual data file. For 30 years, hospital visit data on the utilization and provision of ambulatory care services in hospital emergency departments, outpatient departments, and ambulatory surgery centers were collected as part of NHAMCS through manual medical record abstraction. These data were used to make national estimates on ambulatory visits to U.S. hospitals and were released as an annual public use file (PUF).

An important factor in the sunsetting of NHAMCS is the large-scale use of electronic health records by hospitals and wide availability of electronic hospital encounter data. With hospitals and health care providers storing and sharing data electronically, there is the ability for public health organizations to leverage these electronic data to enhance the understanding of hospital care through the collection of larger amounts of data, as well as the ability to link these data to external sources. Although NHAMCS is ending data collection, emergency department (ED) data collection and estimates will continue to be available at NCHS through the National Hospital Care Survey (NHCS). From a nationally representative sample of hospitals, the NHCS collects data electronically through the integration of various electronic data sources from emergency departments and inpatient hospital settings. Its data can be linked to additional data sources to study hospital-related mortality and the care received at hospitals, including the role of social determinants of health.

Although NHAMCS is ending with the 2022 survey year, data users will still be able to access NHAMCS reports and public use data files from the NCHS website. The 2021 NHAMCS PUF is expected to be released in the summer of 2023. The 2022 NHAMCS PUF is expected to be released in the summer of 2024. In addition, information on the continued collection of hospital data at NCHS can be found on the NHCS website.

Stats of the Month

In recognition of National Women and Girls HIV/AIDS Awareness Day (March 10), we present estimates for visits to emergency departments (ED)  made by patients with HIV/AIDS documented in the medical record from the 2021 National Hospital Ambulatory Medical Care Survey (NHAMCS).

• In 2021, there were approximately 678,000 ED visits made by patients with HIV/AIDS documented in their medical record. About one-quarter (26.9%) of these visits were made by girls and women. (Estimates from the Public Use File).
• In 2021, an HIV test was ordered or provided at 872,000 ED visits. More tests were ordered or provided at ED visits by girls and women (62.8% of all visits with HIV tests) than boys and men (37.2% of all visits with HIV tests) (Estimates from the Public Use File).

Data Tip of the Month

Did you know . . .

A method to analyze drug data involves the isolation of the records with drugs and the creation of a separate data file of drug mentions. Each Patient Record can have up to 30 drug mentions recorded, so whatever file is created would need to include all of them. This method can be used for obtaining estimates of drug mentions but is not recommended for variance estimation. Rather, the structure of the visit file should be kept intact when estimating variance. In order to do this, estimates of drug mentions can be obtained by creating a new weight variable (called DRUGWT in this example). This variable is created by multiplying PATWT (the patient visit weight) by NUMMED (the number of medications recorded at the sampled visit) or DRUGWT=PATWT*NUMMED. DRUGWT can then be used in place of PATWT to weight one’s data; it produces the estimated number of drug mentions rather than visits.

New Products This Month

No new products this month.

Data Tell Stories

Do you have a story to share? How have you used information from the National Ambulatory Medical Care Survey or the National Hospital Ambulatory Medical Care Survey? Email us a brief description at ambcare@cdc.gov. In the subject field of your email, write “My NAMCS/NHAMCS data use example”. Your examples will help us showcase the value of NAMCS and NHAMCS.

Stats of the Month

In recognition of American Heart Month (February), we present estimates for visits to emergency departments (ED) for coronary artery disease, ischemic heart disease, or history of myocardial infarction (MI) from the 2020 National Hospital Ambulatory Medical Care Survey (NHAMCS).

• In 2020, patients with coronary artery disease, ischemic heart disease, or history of MI documented in the medical record accounted for 8.3% of all visits to the ED made by adults. Visits by patients with coronary artery disease, ischemic heart disease, or history of MI increased by age, representing 0.9% of ED visits made by adults aged 18-44, 11.7% of ED visits made by adults aged 45-74 and 24.0% of ED visits made by adults aged 75 and over. (Estimates from the Public Use File)
• In 2020, chest pain and related symptoms was the primary reason for visit in 6.3% of all visits to the ED made by adults aged 18 and over. Visits with chest pain and related symptoms as the primary reason for visit were higher among adults aged 45-74 (7.8%) than among adults aged 18-44 (5.4%) and adults aged 75 and over (4.7%). (Estimates from the Public Use File)

Data Tip of the Month

Did you know . . .

For the 2021 NHAMCS, four items were imputed: age (0.09% of unweighted visit records), sex (0.09%), race (21.4%), and ethnicity (14.4%). Age and sex were imputed using a hot deck based on 3-digit ICD-10-CM code for primary diagnosis, triage level, ED volume, and geographic region. Patient race and ethnicity imputation was performed using a model-based single, sequential regression method. The model used to impute race and ethnicity included the following variables: Census variables for ZIP code level race and ethnicity population estimates and an indicator for whether it was patient or hospital ZIP (used when patient ZIP was not available); patient age, sex, race, and ethnicity; triage level; log of ED wait time; primary expected source of payment derived from a hierarchical recode of the expected source of payment question; grouped 3-digit ICD-10-CM codes for primary diagnosis; year of visit; type of emergency service area; provider’s metropolitan statistical area status; and ED weighting and volume variables.

New Products This Month

No new products this month.

Data Tell Stories

Do you have a story to share? How have you used information from the National Ambulatory Medical Care Survey or the National Hospital Ambulatory Medical Care Survey? Email us a brief description at ambcare@cdc.gov. In the subject field of your email, write “My NAMCS/NHAMCS data use example”. Your examples will help us showcase the value of NAMCS and NHAMCS.

Year in Review

In 2023…

• Various publications were released which used data from the National Ambulatory Medical Care Survey (NAMCS) and from the National Hospital Ambulatory Medical Care Survey (NHAMCS). The publications consisted of NCHS data briefs, NCHS reports, QuickStats, web tables and manuscripts that can be found here or by selecting the publication name below. In 2023, the 2021 NHAMCS Emergency Department public use data file and documentation were made available for downloading, along with SAS, Stata, and SPSS files for reading and formatting the data. Visit-level files based on 2021 NAMCS Health Center Component and 2022 NAMCS Health Center Component data were made available for use in the NCHS Research Data Center (RDC). Restricted data files may be accessed through the Research Data Center.
• Updated dashboards depicting both counts and rates of emergency department (ED) visits from 2016-2021 NHAMCS for the 10 leading primary diagnoses and reasons for visit, stratified by selected patient and hospital characteristics, were made available here. Estimates provided in the visualization highlight and expand on information provided in the annual NHAMCS web tables, which can be used to assess how these categories and rankings changed over the evaluated years.

Publications from NHAMCS and NAMCS in 2023

NCHS Reports, Data Briefs and QuickStats

• Santo L, Schappert SM. Opioids prescribed to adults at discharge from emergency departments: United States, 2017–2020. NCHS Data Brief, no 461. Hyattsville, MD: National Center for Health Statistics. 2023. This report shows that in 2019–2020, the rate of emergency department (ED) visits with opioids prescribed at discharge decreased overall and among women and men compared with 2017–2018.  The percentage of ED visits with opioids prescribed at discharge decreased among all adults, among White non-Hispanic and Black non-Hispanic adults, and among visits according to all primary expected sources of payment.
• Strashny A, Cairns C, Ashman JJ. Emergency department visits with suicidal ideation: United States, 2016–2020. NCHS Data Brief, no 463. Hyattsville, MD: National Center for Health Statistics. 2023. This data brief shows that during 2016–2020, there were, annually, 40 visits per 10,000 people made by patients with suicidal ideation. The visit rate for suicidal ideation was higher among males than females and highest among Black non-Hispanic people. The ED visit rate for suicidal ideation was lowest among hospitals located in the Northeast.
• Davis D, Cairns C. Emergency department visit rates for motor vehicle crashes by selected characteristics: United States, 2019–2020. NCHS Data Brief, no 466. Hyattsville, MD: National Center for Health Statistics. 2023. This data brief shows that in 2019–2020, the annual average ED visit rate for motor vehicle crash injuries was 11.6 visits per 1,000 people. The ED visit rate was highest among patients aged 15–24 years and then declined with age. The visit rate was higher among Black non-Hispanic people, among patients with Medicaid or no insurance as the primary expected source of payment, and among hospitals located in the South.
• Cairns C, Ashman JJ, Peters ZJ. Emergency department visits among children aged 0–17 by selected characteristics: United States, 2019–2020. NCHS Data Brief, no 469. Hyattsville, MD: National Center for Health Statistics. 2023. This data brief highlights changes in ED visits made by children aged 0–17, before and during the first year of the COVID-19 pandemic, a period with limited access to care. The report shows that the ED visit rate among children aged 0–17 decreased from 48 visits per 100 children in 2019 to 31 visits per 100 children in 2020.  The ED visit rates for both boys and girls were lower in 2020 than in 2019.  ED visit rates were also lower for Black non-Hispanic children, White non-Hispanic children, and non-Hispanic children of other races in 2020 than in 2019.
• Cairns C, Ashman JJ, King JM. Emergency department visit rates by selected characteristics: United States, 2021. NCHS Data Brief, no 478. Hyattsville, MD: National Center for Health Statistics. 2023 .This data brief shows that an estimated 43 ED visits per 100 people occurred in 2021. Most visits were made by Black non-Hispanic people and by patients with Medicaid as the primary expected source of payment. The ED visit rate was highest for infants (aged <1 year), followed by adults aged 75 years and over. COVID-19 cases were confirmed at 3.8% of ED visits in 2021.
• Davis D, Santo L. Emergency department visit rates for assault: United States, 2019–2021. NCHS Data Brief, no 481. Hyattsville, MD: National Center for Health Statistics. 2023. This report presents assault-related ED visit rates by selected demographic and hospital characteristics using data from the 2019-2021 NHAMCS. During 2019–2021, there were 4.5 assault-related ED visits per 1,000 people per year. The assault-related ED visit rate was highest for Black non-Hispanic people compared with all other race and ethnicity groups; Medicaid was the most common primary expected source of payment at assault-related ED visits. The assault-related ED visit rate was higher for people who visited hospitals in metropolitan statistical areas compared with nonmetropolitan statistical areas.
• Santo L, Schappert SM, Ashman JJ. Emergency department visit rates by adults with diabetes: United States, 2020–2021. NCHS Data Brief, no 487. Hyattsville, MD: National Center for Health Statistics. 2023. This report highlights differences by age in ED visits made by adults with diabetes. In 2020–2021, the ED visit rate by adults with diabetes was 72.2 visits per 1,000 adults, and the rate increased with age. The ED visit rate by adults with diabetes was highest among Black non-Hispanic people, and the rates increased with age among Black, White, and Hispanic people. The rate of visits by adults with diabetes age 65 and older was higher than all other age groups during 2012–2021 and increased from 113.4 in 2012 to 156.8 in 2021.
• Peters ZJ, Santo L, Davis D, DeFrances CJ. Emergency department visits related to mental health disorders among adults, by race and Hispanic ethnicity: United States, 2018–2020. National Health Statistics Reports; no 181. Hyattsville, MD: National Center for Health Statistics. 2023. This report shows differences by patient race and Hispanic ethnicity in ED visit characteristics related to mental health disorders. The rate of mental health-related ED visits was highest among Black non-Hispanic adults (96.8 visits per 1,000 adults), followed by White non-Hispanic (53.4) and Hispanic (36.0) adults. Rates of ED visits for specific mental health disorders, including substance use disorders, anxiety disorders, and mood disorders, were also highest among Black non-Hispanic adults.
• Ashman JJ, Santo L, Okeyode T. Characteristics of office-based physician visits by age, 2019. National Health Statistics Reports; no 184. Hyattsville, MD: National Center for Health Statistics. 2023. This report describes characteristics of office-based physician visits by using data from the 2019 National Ambulatory Medical Care Survey. In 2019, an estimated 1.0 billion office-based physician visits occurred in the United States. The visit rate among females was higher than for males, and the rates for both infants and older adults were higher than the rates for those aged 1–64. Private insurance was the primary expected source of payment for most visits by children under age 18 and adults aged 18–64, while Medicare was the primary expected source of payment for most visits by adults aged 65 and over. Visits for either chronic conditions or for pre- or post-surgery care increased with age. Visits for either preventive care or a new problem decreased with age.
• Santo L, Peters ZJ, Davis D, DeFrances CJ. Emergency department visits related to mental health disorders among children and adolescents: United States, 2018–2021. National Health Statistics Reports; no 191. Hyattsville MD: National Center for Health Statistics. 2023. This report describes ED visits related to mental health disorders among children and adolescents and compares them with visits by children and adolescents without mental health disorders. Visit rates related to mental health disorders were higher among adolescents ages 12–17 compared with children younger than 12 years, among girls compared with boys, and among Black non-Hispanic children and adolescents compared with Hispanic children and adolescents. At approximately one-quarter of the ED visits by children and adolescents with any diagnosis of a mental health disorder, at least one psychiatric medication was received.
• Strashny A, Beresovsky V, Schappert SM, Santo L. Survey weights in the 2018 National Ambulatory Medical Care Survey adjusted using iterative proportional fitting. National Center for Health Statistics. Vital Health Stat 2(202). 2023. This report describes the adjustment of survey weights for the 2018 National Ambulatory Medical Care Survey using iterative proportional fitting (IPF). Compared with the previous adjustment method, IPF-adjusted weights have a lower maximum value, lower range, lower skewness, and lower design effect suggesting that IPF-adjusted weights produce more efficient estimates. Weight adjustment using IPF produced overall estimates of office-based physicians and their visits that were not significantly different from totals based on the previous method.
• QuickStats: Percentage of Emergency Department Visits with Medicaid as the Primary Expected Source of Payment Among Persons Aged <65 Years, by Race and Ethnicity — National Hospital Ambulatory Medical Care Survey, United States, 2011–2021. MMWR Morb Mortal Wkly Rep 2023;72:853. This QuickStats shows that, during 2011–2021, the percentage of ED visits among persons aged <65 years with Medicaid as the primary expected source of payment increased among all race and ethnicity groups. The percentages of ED visits among Black and Hispanic persons with Medicaid as the primary expected source of payment were higher than the percentages of visits by White persons.
• QuickStats: Rate of Emergency Department Visits by Homeless Status — National Hospital Ambulatory Medical Care Survey, United States, 2010–2021. MMWR Morb Mortal Wkly Rep 2023;72:42. This QuickStats shows that, during 2010–2021, the rate of ED visits by people experiencing homelessness increased from 141 visits per 100 people per year in 2010–2011 to 310 visits per 100 people in 2020–2021. During the same time period, the visit rates for people not experiencing homelessness remained constant, ranging from 42 visits per 100 people per year in 2010–2011 to 40 visits in 2020–2021.
• QuickStats: Rate of Emergency Department Visits for Substance Use Disorders Among Adults Aged ≥18 Years, by Age Group — National Hospital Ambulatory Medical Care Survey, United States, 2018–2019 and 2020–2021. MMWR Morb Mortal Wkly Rep 2023;72:1073. This QuickStats shows that, in 2020-2021, the rate of ED visits with a primary diagnosis of a substance use disorder increased 42% among patients aged 18–34 years and 38% among patients aged ≥35 years since 2018–2019.

Manuscripts  

• Schappert SM, Santo L, Ward BW, Ashman JJ, DeFrances CJ. NHAMCS has been a trusted source of data for healthcare disparities research since 1992. Public Health Nurs. 2023 Jul 26. doi: 10.1111/phn.13231. Epub 2023 Jul 26. PMID: 37495542. This letter to the editor describes how NHAMCS has been a trusted nationally representative data source for healthcare disparities research for more than 30 years. NHAMCS data can be used to perform time series analyses and allow for the study of ED visits among various geographic levels, patient age groups, and racial and ethnic groups. While NHAMCS may not be perfect for every research study, it has a long history of use to study a variety of healthcare topics.

Web Tables

• 2021 NHAMCS EMERGENCY DEPARTMENT SUMMARY TABLES – The most current nationally representative data on ambulatory care visits to hospital emergency departments in the United States were released. Estimates were presented on selected hospital, patient, and visit characteristics using data collected in the 2021 NHAMCS.
• 2019 NATIONAL AMBULATORY MEDICAL CARE SURVEY SUMMARY TABLES – The most current nationally representative data on ambulatory care visits to physician offices in the United States were released. Estimates were presented on selected physician, patient, and visit characteristics using data collected in the 2019 NAMCS.

New Products This Month

Santo L, Schappert SM, Ashman JJ. Trends in emergency department visits among people younger than age 65 by insurance status: United States, 2010–2021. National Health Statistics Reports; no 197. Hyattsville, MD: National Center for Health Statistics. 2024. This report shows Medicaid was the most common primary expected source of payment at ED visits by people younger than age 65  from 2014 through 2021.  Among children younger than age 18 years, the most common primary expected source of payment was Medicaid from 2010 through 2021. The percentage of visits by children with no insurance decreased from 7.4% in 2010 to 3.0% in 2021 . Among adults, the percentage of visits with Medicaid increased from 25.5% in 2010 to 38.9% in 2021, and the percentage of visits by those with no insurance decreased from 24.6% to 11.1% during this period.

Data Tell Stories

Do you have a story to share? How have you used information from the National Ambulatory Medical Care Survey or the National Hospital Ambulatory Medical Care Survey? Email us a brief description at ambcare@cdc.gov. In the subject field of your email, write “My NAMCS/NHAMCS data use example”. Your examples will help us showcase the value of NAMCS and NHAMCS.