An inpatient hospitalization is one in which the patient was admitted to the hospital directly or through the emergency department or other department.

The Emergency Department (ED) Database contains information on ED visits that do not result in admission to the same hospital (i.e., "treated and released," which includes patients who were discharged home, transferred to another health care facility, left against medical advice, left without being seen, transferred to another hospital, or died).

Outpatient and same-day surgery are scheduled in-hospital surgery and the patient is not admitted to the hospital.

Hospital Discharges

The New Jersey Discharge Data Collection System (NJDDCS) database, modeled under the Uniform Billing (UB) database, is the data used for the hospitalization query. The NJDDCS is managed by the Office of Health Care Quality Assessment (HCQA) in the New Jersey Department of Health. The NJDDCS contains information on demographic characteristics of patients, diagnosis and procedure codes following the International Classification of Diseases (ICD), and billing information and charges for services provided.

HCQA receives patient-level hospital discharge data on emergency department (ED), outpatient surgery, same-day surgery and inpatient encounters or episodes. The Inpatient Query only contains discharges in which the person had been admitted to the hospital. The Emergency Department Query only contains visits in which the person was discharged from the ED. If the person is admitted to the hospital from the ED, their record is in the Inpatient Hospitalization part of the query.

Population

Population estimates used to calculate rates are derived from the most recent vintage of the mid-year estimates provided by the U.S. Census Bureau's Population Estimates Program. Estimates are available for each state and its counties by age, race, Hispanic ethnicity, and sex categories. Race and ethnicity can be combined to form seven race/ethnicity groups, where Hispanics may be of any race, the other six groups do not include Hispanics, and data for White, Black, Asian, Native Hawaiian/Pacific Islander, and American Indian/Alaska Native are counts of persons who only selected one of those races (i.e., "alone").

There are separate queries for state and county rates because two different sets of population data are used as denominators in the rate calculations. Population estimates for the state are available by single year of age while estimates for counties are only available in 5-year age groups.

HCQA receives patient-level hospital discharge data on a monthly basis through its data intermediary. Each record is subjected to a series of edits that check for accuracy, consistency, completeness, and conformity with the definitions specified in the New Jersey Discharge Data Collection System. Records failing the edit check are returned to the hospital for corrections and resubmission.

Hospital discharge data are collected for billing purposes, not public health surveillance. Demographic items (age, race, ethnicity, sex, and residence location) should be used with extreme caution as they are only checked by the data intermediary for invalid values. If an item is miscoded with an incorrect but valid value (e.g., American Indian when the patient is Asian Indian), it does not get flagged and remains uncorrected. The NJSHAD team receives datasets from HCQA "as is" with no further quality or edit checks and makes no guarantees as to the accuracy of those variables.

Known errors include:

• Some Monroe Township residents coded as Jamesburg residents, which shares its zip code.

Caveats specific to 2017 data:

• NJDOH changed its vendor for hospitalization data collection in 2017 resulting in data loss at some facilities during the transition period.
• Some hospitals continued to submit data through the old vendor while others planned to submit data through the new vendor. However, the new vendor did not commence data collection until October 1, rather than mid-April as planned, resulting in an inability to submit the full backlog of records by the deadline for hospitals that waited.
• The new vendor's more stringent data quality standards required a new data file format. Some hospitals submitted their data manually while their IT departments updated their systems, but others waited until automated data submission could resume. For some facilities, the system updates were not completed in time to meet NJDOH's data submission deadline.
• Hospitals with ownership changes during this transition period further delayed data submission and, despite NJDOH's extension of the data file closure date several times, those facilities were unable to complete their data submissions in time.
• The old vendor experienced a global malware incident in June 2017 that possibly resulted in the loss of some data in the system queue at that time.

Overall Discharge Volume in 2020:
Hospital claim volume for the 2020 calendar year was markedly lower (19.9%) than for 2019, mostly due to the COVID-19 pandemic. This reduction was seen in both inpatient discharges (8.2% lower claim volume than 2019) and emergency department visits (27.3% lower claim volume than 2019). This was likely the result of hospital care being redirected to address the care for COVID-19 patients while elective surgeries and other outpatient care services were being postponed.

The International Classification of Diseases (ICD) is a coding system maintained by the World Health Organization and the U.S. Centers for Disease Control and Prevention. It is used to classify causes of death on death certificates and diagnoses and injuries for hospital and emergency department visits. These codes are updated every decade or so to account for advances in medical technology.

The U.S. is currently using the 10th revision (ICD-10-CM). The 9th revision (ICD-9-CM) was used for hospital and emergency department visits through September 30, 2015. New Jersey's October 1 - December 31, 2015 records were back-coded to ICD-9-CM, so all 2000-2015 hospital discharge data in NJSHAD indicator reports were coded using ICD-9-CM. All data for 2016 forward are coded using ICD-10-CM. While some code groups are fairly comparable from ICD-9 to ICD-10, some, such as those for asthma, COPD, and congestive heart failure, are not. Caution should be used when examining trends.

A race group (White, Black/African American, American Indian/Alaska Native, Asian Indian, Chinese, Filipino, Japanese, Korean, Vietnamese, Other Asian, Native Hawaiian, Guamian/Chamorro, Samoan, Other Pacific Islander, Multiracial: White and Black/African American, Multiracial: White and American Indian/Alaska Native, Multiracial: White and Asian, Multiracial: Black/African American and American Indian/Alaska Native, Other Race, Unknown/Unavailable, and Declined to Answer) and an ethnicity (Non-Hispanic, Mexican, Puerto Rican, Cuban, Central or South American, other Hispanic, Unknown/Unavailable and Declined to Answer) are recorded for each individual for whom a hospitalization record is filed. In order to standardize reporting, race and ethnicity categories are used together to create mutually exclusive categories including a Hispanic "race" category as is customary in reporting such data by the New Jersey Department of Health.

Race/ethnicity designations used in the hospitalization query are White, Black, Hispanic, Asian, Native Hawaiian/Other Pacific Islander, American Indian/Alaska Native, Two or More Races, and Other Race, where Hispanics may be of any race and the other race groups do not include Hispanics (but include those with ethnicity unknown). The Hispanic category includes persons of Mexican, Puerto Rican, Cuban, Central/South American, or other Hispanic ethnicity, regardless of race. The Asian category includes persons of Asian Indian, Chinese, Filipino, Japanese, Korean, Vietnamese, and other Asian descent. The Native Hawaiian/Other Pacific Islander category includes persons of Hawaiian, Guamian, Samoan, and other Pacific Islander descent. The Two of More Races category includes all four multiracial categories. The Other Race category includes all race groups other than White, Black, Asian, Native Hawaiian/Pacific Islander, American Indian/Alaska Native, and the four Multiracial groups. When combining race and ethnicity, Hispanic ethnicity takes precedence over whatever race is recorded for the patient.

For public health planning and policy determination, the most useful population to study is usually the resident population of an area. Although there are limited hospitalization data exchange agreements among neighboring states, the NJDDCS does not contain hospitalizations that occurred out of state. The query system provides data only on hospital encounters of New Jersey residents that occurred in New Jersey hospitals and does not fully capture all hospitalizations of New Jersey residents.

Allocation of data by place of residence within the state is sometimes difficult because classification depends on the statement of the usual place of residence provided at the time of hospitalization. For a variety of reasons, the information provided may be incorrectly recorded. Another common problem occurs when patients use mailing address for residence address. Currently, there is no mechanism implemented to correct hospitalization data files by running them through geocoding software to properly assign the county and municipality of residence. The place of residence information should be used with caution.