Prevalence of Undiagnosed HIV Infection Among Persons Aged ≥13 Years — National HIV Surveillance System, United States, 2005–2008

Mi Chen, MS1

Philip H. Rhodes, PhD1

H. Irene Hall, PhD1

Peter H. Kilmarx, MD2

Bernard M. Branson, MD1

Linda A. Valleroy, PhD1

1Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention

2Division of Global HIV/AIDS, Center for Global Health

Corresponding author: Mi Chen, MS, Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, CDC, 1600 Clifton Rd, MS E-47, Atlanta, GA 30333. Telephone: 404-639-8336; Fax: 404-639-2980; E-mail: bli0@cdc.gov.

Introduction

In the United States, approximately 1.1 million adults and adolescents are living with human immunodeficiency virus (HIV) infection and, each year, another 50,000 become infected (1). At the end of 2008, approximately 20% of the persons living with HIV had an undiagnosed infection (2). Of those living with HIV at the end of 2008, nearly two thirds were racial/ethnic minorities and half were men who have sex with men (MSM) (2). In 2007, HIV ranked fifth as a leading cause of death among persons aged 35–44 years in the United States but third among blacks or African Americans in this age group (3). In 40 states with longstanding confidential name-based HIV surveillance systems, 33% of the estimated 41,768 adults and adolescents diagnosed with HIV infection in 2008 developed acquired immunodeficiency syndrome (AIDS) within 1 year (4) and, of these, 44% received their initial diagnosis in an acute care setting, suggesting that they received HIV testing late in the course of the infection. HIV-infected persons who are unaware of their infection or who receive a late diagnosis cannot benefit fully from timely initiation of therapy and are more likely to experience HIV-related morbidity and premature mortality (5). In addition, persons unaware of their infection are more likely to transmit HIV to others because of a higher prevalence of high-risk sexual behaviors (6) and higher levels of viral RNA that continue to replicate without appropriate antiretroviral treatment (7).

This report describes prevalence trends in HIV infection in the United States during 1985–2008 among persons aged ≥13 years who were aware of their infection (i.e., diagnosed HIV infection) and unaware of their infection (i.e., undiagnosed HIV infection) and the characteristics of persons living with diagnosed and undiagnosed HIV infection in 2008. For local and state public health officials and for providers, these estimates can serve as the baseline for focusing efforts and monitoring progress of interventions designed to increase HIV testing, expand HIV screening in health-care settings, and increase early diagnoses of HIV infection.

Methods

To examine the prevalence trends of both diagnosed and undiagnosed HIV infection during 1985–2008 among persons aged ≥13 years and to describe the characteristics of persons aged ≥13 years estimated to be living with diagnosed and undiagnosed HIV infection in 2008, CDC analyzed data from the National HIV Surveillance System, a population-based surveillance system that collects data on persons who have received a diagnosis of HIV infection in the United States. HIV infection is notifiable in all 50 states and the District of Columbia (DC). CDC uses HIV data from states that have had confidential name-based HIV infection reporting for at least 4 years to allow sufficient time to elapse for the calculation of accurate estimates of reporting delays and the reliable determination of trends. Consistent with this requirement, this report includes HIV and AIDS data reported through June 2010 for persons aged ≥13 years at diagnosis from 40 states that had confidential name-based HIV infection reporting as of January 2006 and AIDS data from DC and the 10 other states (California, Delaware, Hawaii, Maryland, Massachusetts, Montana, Oregon, Rhode Island, Vermont, and Washington).

The estimates for the overall HIV prevalence and undiagnosed HIV prevalence at the end of 2008 were obtained in four steps. First, HIV and AIDS data were statistically adjusted to mitigate the effects of 1) delays in reporting new cases and deaths (4), 2) incomplete reporting of diagnosed cases (8), and 3) cases reported without sufficient risk factor information to be classified into an HIV transmission category (4). Second, based on the estimated annual number of HIV diagnoses and the severity of disease at diagnosis (i.e., whether the person received an AIDS diagnosis in the same calendar year as the HIV diagnosis), an extended back-calculation model was fitted to estimate the cumulative number of persons aged ≥13 years who had been infected with HIV by the end of 2008 (8). Third, the estimated overall HIV prevalence was calculated by subtracting the estimated cumulative number of deaths that had occurred among those infected by the end of 2008 from the estimated cumulative number of HIV infections. Finally, the undiagnosed HIV prevalence was calculated by subtracting the estimated number of diagnosed HIV infections in living persons from the estimated overall HIV prevalence.

Rates per 100,000 population were calculated based on postcensal estimates from the U.S. Census Bureau. The type of facility where persons were initially diagnosed with HIV infection in 2008 in the 40 states was examined using univariate and multivariate log-binomial regression models. Prevalence ratios and 95% confidence intervals (CIs) were calculated to identify factors that were associated with receiving a diagnosis in an acute care setting; an acute care setting included hospital inpatient rooms and emergency departments. Factors included in the models were age at diagnosis, sex, race/ethnicity, HIV transmission category, and timeliness of HIV testing. Persons were classified as testing late in the course of HIV infection (i.e., late testers) if AIDS was diagnosed within 1 year of the initial HIV infection diagnosis. A chi-square test for homogeneity was used to determine whether the characteristics of persons whose type of facility of diagnosis was known differed significantly from those of persons whose type of facility of diagnosis was unknown. Statistical significance was set at p<0.05.

Results

In the United States, the estimated number of persons aged ≥13 years living with HIV infection, including those whose infection had not been diagnosed, increased from 420,153 in 1985 to 1,178,250 in 2008 (Figure). HIV prevalence increased by an estimated 55.4% between 1996 (758,283), when highly active antiretroviral therapy became widely available in the United States, and 2008. Although the estimated percentage of undiagnosed HIV infections has decreased substantially, from 87.9% in 1985 to 20.1% in 2008, the percentage persisted at approximately 20% from 2004 to 2008.

The majority of the 1,178,250 persons aged ≥13 years living with HIV infection at the end of 2008 were male (75%), racial/ethnic minorities (66%), and aged 35–54 years (63%) (Table 1). MSM represented 66% of the 883,300 males estimated to be living with HIV infection, and black or African American females represented 64% of the 294,800 females. At the end of 2008, a total of 2,536.1 per 100,000 black or African American males and 897.3 per 100,000 Hispanic or Latino males were living with HIV infection, compared with 419.4 per 100,000 white males. Correspondingly, the rate of HIV prevalence among black or African American females (1,184.9 per 100,000) and Hispanic or Latino females (263.1 per 100,000) were 18 times and 4 times the rate among white females (66.4 per 100,000), respectively. Compared with the overall 20.1% undiagnosed HIV infection prevalence, greater percentages of undiagnosed HIV infection were observed among persons aged <35 years (13–24 years: 58.9%; 25–34 years: 31.5%), black or African American MSM (25.7%), men with high-risk heterosexual contact (24.9%), American Indians or Alaska Natives (25.0%), and Asians or Pacific Islanders (25.9%). The prevalence rate of undiagnosed HIV infection was highest among black or African American males (570.7 per 100,000), black or African American females (228.8 per 100,000), and Hispanic or Latino males (177.8 per 100,000) and lowest among Asian or Pacific Islander females (12.6 per 100,000) and white females (10.9 per 100,000).

The type of facility of initial diagnosis was known for 32,647 (78.1%) of the estimated 41,768 persons aged ≥13 years whose HIV infection was diagnosed in 2008 in the 40 states (Table 2). The majority (74.3%) of diagnoses occurred in a clinical setting, almost one fourth each in an acute care setting (24.8%) and at a private doctor's office or health maintenance organization (HMO) (24.3%). The probability of initial diagnosis in an acute care setting was significantly higher among persons aged ≥55 years at diagnosis compared with persons aged 35–44 years (55–64 years: prevalence ratio [PR] =1.22, 95% CI = 1.15–1.29; ≥65 years: PR = 1.39, 95% CI = 1.28–1.51), blacks or African Americans (PR = 1.21, 95% CI = 1.15–1.26), and Hispanics or Latinos (PR = 1.17, 95% CI = 1.10–1.23) compared with whites, persons with a history of injection drug use compared with MSM (PR = 1.36, 95% CI = 1.29–1.44), and late testers compared with persons who were not late testers (PR = 2.53, 95% CI = 2.43–2.63).

Discussion

HIV diagnosis is essential as the entry point for a lifelong continuum of care and treatment that benefits the health, quality of life, and life expectancy of the infected person and reduces the likelihood of HIV transmission to others (5–7). However, in the United States, the engagement of HIV-infected persons in this continuum of care for HIV infection needs improvement. As indicated by the findings in this report, approximately 80% of persons infected with HIV are aware of their infection. Furthermore, only approximately 77% of HIV-diagnosed persons are linked to care within 3–4 months after diagnosis, and only approximately 51% of those with a diagnosis of HIV infection are engaged in long-term care (9). Among persons in care, approximately 89% are prescribed antiretroviral medications and of these, approximately 77% achieve plasma viral load suppression (≤200 copies/mL) (9). Overall, only approximately 28% of HIV-infected persons in the United States are aware of their infection, are in care, are receiving antiretroviral therapy, and have a suppressed HIV viral load (9).

To increase HIV testing and promote early detection of HIV infection, in 2006, CDC recommended routine HIV screening for all patients aged 13–64 years in health-care settings with a prevalence of undiagnosed HIV infection of ≥0.1%, all pregnant women, and patients initiating or seeking treatment for tuberculosis or sexually transmitted infections (10). The U.S. Preventive Services Task Force (USPSTF) also released recommendations in 2005 (rated as strongly recommended, or grade A recommendations, by USPSTF) for HIV screening of all pregnant women and all adults and adolescents at increased risk for HIV infection and those seen in health-care settings with ≥1% prevalence of infection (11). CDC further recommended in 2006 that persons at high risk for HIV infection should be screened at least annually (10). However, among the 7,271 MSM who were surveyed and tested for HIV infection by the National HIV Behavioral Surveillance System (NHBS) in 21 U.S. cities in 2008 and who did not report having received a diagnosis of HIV infection in the past, only 61% had been tested during the preceding 12 months and of these, 7% received their first HIV-positive result as part of NHBS (12).

To guide local, state, and national efforts to increase the percentages of persons engaged in the continuum from HIV diagnosis to viral load suppression, the 2010 National HIV/AIDS Strategy (13) emphasizes prevention and intervention service provision at clinics, community centers, and nontraditional settings (e.g., mental health centers). These services include HIV testing, as well as linkage to and retention in long-term quality care that seeks to sustain viral load suppression through promotion of adherence after timely initiation of antiretroviral therapy and provision of coordinated care for therapy-associated complications, other coinfections, substance addiction, and mental health issues. HIV testing of all pregnant women and treatment of HIV-infected pregnant women is essential to prevent perinatal transmission. Other prevention services that can be incorporated into health care include HIV risk behavior assessment and risk reduction counseling, condom distribution for HIV-infected and -uninfected persons and a broad array of partner services. New and emerging preventive care in health-care settings includes preexposure prophylaxis for at-risk MSM and male circumcision (14–17).

The Patient Protection and Affordable Care Act of 2010 as amended by the Healthcare and Education Reconciliation Act of 2010 (referred to collectively as the Affordable Care Act [ACA]), which was signed into law in March 2010, creates an opportune environment for implementing the National HIV/AIDS Strategy and makes its goals more achievable. Under the new law, persons who are living with or at increased risk for HIV infection such as young minority men will be more likely to be screened for HIV and to receive life-saving treatment and services that strengthen their ability to adhere to treatment regimens. The law provides greater health-care access to those who are currently uninsured or underinsured by

• expanding Medicaid coverage to persons with incomes ≤133% of the federal poverty level (FPL) (ACA §2001);
• establishing state-based health insurance exchanges (ACA §1311) to make private health insurance available to small employers and to individuals and families not eligible for Medicaid or the Children's Health Insurance Program and providing tax credits for those at 100%–400% of FPL; and
• increasing funding to community health centers (ACA §5601).

The Affordable Care Act provides for no cost sharing for high-value clinical preventive services, including HIV testing for adolescents and adults at increased risk for HIV infection. Medicare now covers adult clinical preventive services graded A (strongly recommended) or B (recommended) by USPSTF and vaccinations recommended by the Advisory Committee on Immunization Practices, with no cost sharing to beneficiaries. These services, in addition to recommended preventive services for children, youths, and women, will be covered with no cost sharing by newly qualified private health plans operating in the state-based insurance exchanges beginning in 2014. Beginning in 2013, state Medicaid programs that eliminate cost sharing for these clinical preventive services may receive enhanced federal matching funds for them.

Furthermore, the new law demands more provider accountability for factors within their control and commences more improvements in the health outcomes of HIV-infected persons through well-timed, better, and safer care. The law calls for

• the National Strategy for Quality Improvement in Health Care (ACA §3011) to prioritize, guide, and coordinate local, state, and national efforts to promote the most effective prevention and treatment practices for the leading causes of death in the United States and reduce health disparities;
• the development of standards to measure the performance of clinicians, service providers, health plans, and population health (ACA §3013);
• the improvement of public reporting initiatives that enable consumers to review and compare clinician and service provider performance (ACA §3015);
• the establishment of community-based health teams to support primary care practices (ACA §3502); and
• the implementation of medication management through licensed pharmacists (ACA §3503).

The findings in this report are subject to at least four limitations. First, HIV data used in the extended back-calculation represent only a portion of persons in the United States who received a diagnosis of HIV infection; several high-morbidity areas such as California, DC, and Maryland contributed AIDS data but not HIV data because confidential name-based HIV infection reporting was not implemented in these areas until after January 2006. The availability of reported HIV data from these areas will increase the accuracy of future national prevalence estimates. Second, not all HIV-infected persons have received a diagnosis of infection and been reported to the public health surveillance systems; data must be estimated for persons whose infection is undiagnosed. Third, statistical uncertainties were introduced in the estimates because data were adjusted for reporting delays, incomplete reporting, and missing HIV transmission category information. Finally, the type of facility where HIV infection was diagnosed initially was unknown for 22% of persons aged ≥13 years who received their diagnosis in 2008 in the 40 states. However, except for a higher percentage of late testers among persons with unknown facility type (35% vs. 32%, p<0.001), no significant difference in demographic characteristics and HIV transmission category was found between persons whose type of facility of diagnosis was known and persons whose type of facility of diagnosis was unknown.

Conclusion

HIV diminishes quality of life and productivity, increases the number of preventable deaths, and increases health-care expenditures. Based on the estimated incidence of HIV infection in 2009 (1) and the adjusted lifetime cost of HIV care in the United States to reflect 2010 U.S. dollars (18), CDC estimates that the total cost for treating HIV infection in the United States is $18.3 billion per year. To reduce the number of new HIV infections and thereby the ultimate cost of HIV, the National HIV/AIDS Strategy intends to increase 1) the percentage of persons living with HIV infection who know their serostatus to 90%; 2) the percentage of persons with a new HIV diagnosis who are linked into clinical care within 3 months of their diagnosis to 85%; 3) the percentage of Ryan White HIV/AIDS program (19) clients who are in continuous care to 80%; and 4) the percentage of HIV-diagnosed MSM, blacks or African Americans, and Hispanics or Latinos with undetectable viral load by 20% by 2015. These targets will not be met without the expansion of HIV prevention and intervention service delivery in health care. Only by combining expertise and efforts can public health professionals and health-care providers ensure greater public awareness of HIV infection and risk reduction, eliminate HIV-related stigma and discrimination, expand opportunities for HIV testing, increase the frequency of testing in high-risk populations, and establish a seamless prevention, intervention, care, and treatment infrastructure through which every HIV-infected person is able to receive the right care and support at the right time.

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