Opioid-involved Emergency Department Visits in the National Hospital Care Survey and the National Hospital Ambulatory Medical Care Survey

Questions for Geoffrey Jackson, Health Statistician and Lead Author of “Opioid-involved Emergency Department Visits in the National Hospital Care Survey and the National Hospital Ambulatory Medical Care Survey.”

Q: Why did you decide to research opioid-involved emergency department (ED) visits?

GJ: From 2005 through 2014, it is estimated that the rate of ED visits due to opioid use increased 99.4%, from 89.1 per 100,000 population in 2005 to 177.7 per 100,000 population in 2014. We were struck by the large increase and know that ED data can provide critical information on opioid use-related treatments, such as opioid use disorder treatment, detoxification for safe opioid withdrawal, and management of adverse effects. NCHS hospital surveys can be used to monitor trends in opioid overdoses, as well as other opioid-related morbidity and mortality measures.


Q: Can describe the difference between the difference between the National Hospital Care Survey and the National Hospital Ambulatory Medical Care Survey?

GJ: Even though both surveys collect data from hospital emergency departments, the mode of data collection differs between the two surveys. The National Hospital Care Survey (NHCS) is an all-electronic data collection of administrative claims or billing data. NCHS receives all inpatient, ED, and outpatient hospitals for a calendar year.  In addition, to patient demographics, diagnoses, procedures, laboratory tests, and medications, NHCS collects patient name, address, and Social Security number, which allows patients to be followed over time and linkage to external data sources, such as the National Death Index, providing a more complete picture of patient care and post-acute mortality.

In contrast, the National Hospital Ambulatory Medical Care Survey (NHAMCS) data collection relies on medical record abstraction by U.S. Census Bureau field representatives during a 4-week period. A random sample of about 100 ED visits are selected from all visits during the reporting period, and data are manually abstracted directly from medical records by Census staff. NHAMCS collects similar information as NHCS, but NHAMCS does not collect patient identifiers.  As a consequence, NHAMCS data cannot be linked to other sources nor can patients be collected over time.


Q: Was there a specific finding in the data that surprised you from this report?

GJ: One finding that surprised me was the increase in percentage the patients that died of an opioid overdose 90 days after their hospital visits. Specifically, of the patients with an opioid-involved ED visit that died with 91 and 365 days after their ED visit, 20.6% died with an opioid overdose, compared to approximately 15% that died within 90 days post-ED visit died of an opioid overdose.


Q: Is this the most recent data you have on this topic?

GJ: The most recent NHCS data available in the NCHS Research Data Center (RDC) are from 2016. The 2016 NHCS data are linked to the 2016 and 2017 National Death Index and include information on specific drugs mentioned on the death certificate from the Drug-Involved Mortality file. Additionally, the 2016 NHCS RDC data include identification of opioids using an enhanced methodology that uses natural language processing and machine learning techniques. The most recent NHAMCS public use data file available are from 2018.


Q: What is the take home message for this report?

GJ: NHCS is an important data source for studying opioid-involved ED visits. Through the collection of patient identifiers, the data can be linked to the National Death Index to provide information on post-acute mortality. The information on post-acute mortality is not available in other hospital data sources. Even though the NHCS data are not nationally representative, the NHCS data have similar distributions to NHAMCS data for national estimates of ED visits of male and female opioid-involved ED visits and for persons aged 35 and over.

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