Social Determinants of Health among Adults with Diagnosed HIV Infection, 2018: Technical Notes

A. Geocoding of HIV Surveillance Data Overview

CDC funds state and local health departments to conduct HIV surveillance, and jurisdictions geocode to the census tract level the address of residence at the time of diagnosis. This report includes data for persons aged 18 years and older whose HIV infection was diagnosed during 2018 and reported to the NHSS through December 2019 from the 50 states, the District of Columbia, and Puerto Rico.

After a census tract was assigned to each person’s residence at the time of HIV diagnosis (2018), data were linked with the ACS estimates for 2014–2018 to assign a value for each of the SDH indicator variables to each person with diagnosed HIV infection. Cases or census tracts were excluded if the address was nonresidential (e.g., military base, corrections facility), no census tract was associated with the case, no SDH information was available for the census tract, or the census tract from the surveillance data could not be matched to a census tract provided by the ACS. Although HIV diagnosis data associated with these exclusions were not included in all SDH subpopulation totals, they were included in the overall subtotals stratified by sex at birth. Therefore, all tables display differing denominators for SDH subpopulation categories.

B. Social Determinants of Health Indicator Variables

SDH indicator variables [15] and definitions [16] were obtained from the ACS. This report uses data from the 2014–2018 ACS estimates. The 5-year estimates were used because census tract data are only available at this level (1-year census tract-level estimates are not available). The U.S. Census Bureau collected these data during the 5 years and created period estimates based on the information collected. Period estimates are estimates based on information collected over time (60 months for this report) [17]. Period estimates were not calculated as an average of 60 monthly values; the U.S. Census Bureau collected survey information continuously and then aggregated the results over a specific period (5 years) [16]. The data collection was spread evenly across the entire period so as not to over-represent any particular year within the period. All areas were sampled regardless of population size.

B1. SDH VARIABLES AND DEFINITIONS

For this report, the SDH indicator variables were categorized by using empirically derived quartiles, and each quartile cut-point was rounded to the nearest integer. The quartile cut-points were determined by using data from all census tracts in the 50 states, the District of Columbia, and Puerto Rico and not just from the data applicable to persons in this report (i.e., persons with an HIV diagnosis). This report presents 5 SDH indicator variables: federal poverty status, education level, median household income, health insurance coverage, and Gini index.

• Federal poverty status: proportion of residents in the census tract who were living below the U.S. poverty level (i.e., below a specified threshold) during the 12 months before the survey response (individuals aged 18 years and older)
• Education level: proportion of residents in the census tract with less than a high school diploma (individuals aged 18 years and older)
• Median household income: median income for a household within the census tract during the 12 months before the survey response
• Health insurance coverage: proportion of residents in the census tract without health insurance or health coverage plan (individuals aged 18 years and older)
• Gini index: proportion of household income distribution within the census tract during the 12 months before the survey response

B1.1 Poverty

The percentage of the population aged 18 years and older who were living below the poverty level was determined by using the U.S. Census Bureau’s set of dollar-value thresholds (i.e., income cutoffs) that vary by family size and composition to determine who lives below the poverty level. A person’s poverty status is determined by comparing the person’s total family income during the 12 months before the survey response with the poverty threshold appropriate for that person’s family size and composition. If the total income of that person’s family is less than the threshold appropriate for that family, then the person, together with every member of his or her family, is considered “below the poverty level.” In the Census Bureau’s determination of poverty status, the following populations were excluded: (1) institutionalized persons, (2) persons residing in military group quarters, (3) persons in college dormitories, and (4) unrelated persons aged less than 15 years. The U.S. Census Bureau defines poverty areas as census tracts with poverty levels of 20% or more [18].

B1.2 Education

The percentage of persons with less than a high school diploma was defined as the percentage of persons aged 18 years and older who were not enrolled in school and were not high school graduates. These people may be referred to as “high school dropouts.” No restriction is placed on when they “dropped out” of school; therefore, they may have dropped out before high school and never attended high school.

B1.3 Household Income

The median household income was determined by dividing the income distribution into 2 equal parts: one-half of the households in the census tract fall below the median income and one-half above the median. The median income was based on the income distribution of the total number of households, including those with no income.

B1.4 Health Insurance Coverage

The percentage of persons aged 18 years and older without health insurance coverage was determined based on the number of persons without plans or programs that provide comprehensive health coverage (both private health insurance and public coverage). Insured persons include: (1) insurance through a current or former employer (of this person or another family member) or union, (2) insurance purchased directly from an insurance company (by this person or another family member), (3) Medicare, for persons aged 65 years and older, or persons with certain disabilities, (4) Medicaid, Medical Assistance, or any kind of government-assistance plan for those with low income or a disability, (5) TRICARE or other military health care, and (6) U.S. Department of Veterans Affairs (VA), including those who have ever used or enrolled for VA health care. Persons who had no reported health coverage, or those whose only health coverage was Indian Health Service, were considered uninsured. Also, plans that provide insurance for specific conditions or situations, such as cancer and long-term care policies, are not considered coverage. Likewise, other types of insurance, like dental, vision, life, and disability insurance, are not considered health insurance coverage. The population estimates for health insurance coverage excludes active-duty military personnel and the population living in correctional facilities and nursing homes.

B1.5 Gini Index

The Gini index of income inequality measures the dispersion of the household income distribution. The Gini index, or index of income concentration, is a statistical measure of income inequality ranging from 0 (or 0%) to 1 (or 100%). A measure of 1 indicates perfect inequality; i.e., one household having all the income and rest having none. A measure of 0 indicates perfect equality; i.e., all households having an equal share of income. The Gini index is based on the difference between the Lorenz curve (the observed cumulative income distribution) and the straight line denoting a perfectly equal income distribution. This measure is presented for household income.

C. Tabulation and Presentation of Data

The data in this report include information received by CDC through December 31, 2019, and include 2 data populations:

1. Tables 1–8, S1–B3 include data for the 50 states, the District of Columbia, and Puerto Rico.
   • ACS SDH data (Tables S1–S5) were obtained directly from the U.S. Census Bureau’s 2014–2018 ACS estimates [15].
   • Diagnoses of HIV infection, by race/ethnicity, selected characteristics, and selected SDH are displayed in Tables A1–B3.
2. Tables 9a–10d (linkage to HIV medical care within 1 month of HIV diagnosis and viral suppression within 6 months of HIV diagnosis) include data for those jurisdictions with complete laboratory reporting.
   • As of December 2019, 42 jurisdictions (41 states and the District of Columbia) had met the criteria for the collection and reporting of CD4 and viral load test results: The 41 states are Alabama, Alaska, California, Colorado, Delaware, Florida, Georgia, Hawaii, Illinois, Indiana, Iowa, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Virginia, Washington, West Virginia, Wisconsin, and Wyoming.
   • More information on calculating linkage to HIV medical care and viral suppression can be found at Monitoring selected national HIV prevention and care objectives by using HIV surveillance data—United States and 6 dependent areas, 2018 pdf icon[PDF – 4 MB].

Please use caution when interpreting numbers less than 12, and rates based on these numbers.

C1. Definitions and Data Specifications

C1.1 Diagnoses

The term diagnosis of HIV infection is defined as a diagnosis of HIV infection regardless of the stage of disease (stage 0, 1, 2, 3 [AIDS], or unknown) and refers to all persons with a diagnosis of HIV infection.

More information on counting diagnoses of HIV infection can be found in the Technical Notes of the 2018 HIV Surveillance Report at https://www.cdc.gov/hiv/library/reports/hiv-surveillance/vol-31/index.html.

C1.2 Linkage to HIV Medical Care and Viral Suppression within 6 months of diagnosis

The data on linkage to HIV medical care were based on persons whose infection was diagnosed during 2018 and who resided in any of 42 jurisdictions at the time of diagnosis that reported complete CD4 and viral load laboratory results to CDC. Linkage to HIV medical care within 1 month after HIV diagnosis was measured by documentation of ≥1 CD4 (count or percentage) or viral load tests performed ≤1 month after HIV diagnosis, including tests performed on the same date as the date of diagnosis.

Viral suppression within 6 months of diagnosis was measured for persons whose infection was diagnosed during 2018 and who resided in any of the 42 jurisdictions at time of diagnosis. Viral suppression was defined as a viral load result of <200 copies/mL at any viral load test within 6 months of an HIV diagnosis made during 2018.

More information on calculating linkage to HIV medical care and viral suppression can be found at https://www.cdc.gov/hiv/pdf/library/reports/surveillance/cdc-hiv-surveillance-supplemental-report-vol-25-2.pdf pdf icon[PDF – 4 MB] (Monitoring selected national HIV prevention and care objectives by using HIV surveillance data—United States and 6 dependent areas, 2018).

C2. RATES

Rates per 100,000 population were calculated for the numbers of diagnoses of HIV infection. The population denominators used to compute these rates for the 50 states, the District of Columbia, and Puerto Rico were based on the 5-year estimated total population for those areas [15]. The denominators used for calculating age-, sex-, and race/ethnicity-specific rates were computed by applying the 5-year estimates for age, sex at birth, and race/ethnicity for these areas [15]. Reported numbers less than 12, and rates based on these numbers, should be interpreted with caution.

Subpopulation stratifications of race data by [age group and] sex at birth from the 2014–2018 estimates from the ACS for racial groups other than whites may include Hispanics/Latinos. As a result, there may be overlap in populations for these racial groups and Hispanics/Latinos and, therefore, diagnosis rates by race/ethnicity (Table 1) should be interpreted with caution. Of the denominator population from this ACS in this report, for American Indians/Alaska Natives, 21.1% were Hispanic/Latino (20.9% when Puerto Rico is excluded); for Asians, 1.2% were Hispanic/Latino (1.2% when Puerto Rico is excluded); for Blacks/African Americans, 3.8% were Hispanic/Latino (2.9% when Puerto Rico is excluded); and for Native Hawaiians/other Pacific Islanders, 9.9% were Hispanic/Latino (9.9% when Puerto Rico is excluded). Finally, the denominator population from the ACS is based on the entire population aged 18 years and older; the numerator population is limited to persons whose HIV infection had been diagnosed and reported, with complete residential address, to the NHSS. Because the ACS uses predetermined age categories and varying criteria for SDH variables, the denominators differ for some SDH variables.

D. Demographic Information

D1. Age

All tables in this report reflect data for persons aged 18 years and older (i.e., adults). This report was limited to adults aged 18 years and older with diagnosed HIV infection to more accurately represent the population from which data are collected for ACS SDH indicator variables. For tables that provide data by age group, the specific age-group assignment (e.g., 18–24 years) was based on that person’s age at the time of HIV diagnosis.

D2. Sex

Sex designations in this report are based on a person’s sex at birth.

D3. Race and Ethnicity

The data presented in this report were collected using the Office of Management and Budget’s revised 1997 standards for ethnic and racial data, which calls for splitting Asian/Pacific Islander into 2 categories (Asian and Native Hawaiian/other Pacific Islander) and collecting 2 categories of ethnicity (Hispanic or Latino and not Hispanic or Latino) [19]. Hispanics and Latinos can be of any race.

Due to confidentiality concerns, the ACS [age- and] sex-specific population counts for racial groups other than whites may include Hispanics/Latinos.  Therefore, race-specific diagnosis rates (except whites) should be interpreted with caution. Also, the number of persons reported in each race category may include persons whose ethnicity was not reported.

D4. Transmission Categories

Information on transmission categories can be found in the Technical Notes of the 2018 HIV Surveillance Report at https://www.cdc.gov/hiv/library/reports/hiv-surveillance/vol-31/index.html).

E. Geographic Designation

E1. Census Tract

Data presented in this report reflect the census tract of the person’s residential address at the time they received an HIV diagnosis. A census tract is a standard area used by the U.S. Census Bureau for the purpose of counting the population. Census tracts are small, relatively permanent statistical subdivisions of a county delineated by local participants as part of the U.S. Census Bureau’s Participant Statistical Areas Program. Census tracts must stay within a county and therefore a state. They do not necessarily coincide within any other geography. For example, although some census tracts follow place boundaries, there is no rule that says they must stay within a place. Census tracts are designed to be relatively homogeneous units with respect to population characteristics, economic status, and living conditions at the time of establishment. Each census tract generally contains 1,500 to 8,000 inhabitants (average, 4,000 inhabitants) [20].