For persons with HIV infection, ongoing HIV medical care is vital in reducing HIV-related morbidity and mortality, achieving optimal health outcomes, and preventing transmission.1–8 Viral suppression is the ultimate goal in a care and treatment continuum that includes diagnosis, linkage to care, subsequent and ongoing medical care, and antiretroviral therapy (ART).6–8
Measuring engagement in the HIV care continuum at the national level requires standardized definitions that are applicable across jurisdictions. Much work has been conducted leading to the development of these standard definitions for the United States; however, 1 measure—retention in care—continues to be revised and defined differently by various stakeholders.9–11 Currently, 2 definitions exist for measuring retention in care at the national level. The National HIV/AIDS Strategy (NHAS) and the Institute of Medicine define retention in care as documentation of ≥2 care visits ≥3 months apart during the most recent year.9,10 In contrast, the US Department of Health and Human Services (HHS) defines retention in its Core Indicators as “≥1 CD4 T-lymphocyte (CD4) or viral load (VL) test in each 6-month period of a 24-month measurement period, with a minimum of 60 days between the first test date in the prior 6-month period and the last test date in the subsequent 6-month period.”11 Although the National Quality Forum has endorsed the HHS Core Indicator as the common indicator for HHS-funded HIV programs and services,12 no analysis to date has evaluated the application of this definition to HIV surveillance data for monitoring retention in care.
Applying the NHAS and Institute of Medicine definition to HIV surveillance data and using CD4 and VL laboratory data as indicators of care visits, the Centers for Disease Control and Prevention (CDC) recently published results of analyses illustrating that 50.9% of 338,959 persons living with diagnosed HIV infection (PLWH) in 19 US jurisdictions were retained in care during 2010.13 Also among these 338,959 PLWH, only 43.4% were virally suppressed. Among PLWH who had received any care (≥1 CD4 or VL test) in 2010, a much higher percentage (68.5%) had achieved viral suppression. The report did not present viral suppression data for PLWH who were considered retained in care nor did it discuss the potential and probable gap in viral suppression between persons retained in care and persons who had ≥1 care visit during the year (but who were not considered “retained in care”). However, because achieving viral suppression is key for longevity and reduced transmission, it is important to identify the level of care engagement that will best help persons with HIV reach this goal.
Routine clinical monitoring for persons with well-controlled HIV infection may occur less frequently than for persons with uncontrolled infection. Recent data and clinical guidelines suggest that CD4 and VL monitoring can occur less frequently for patients who are adherent to ART and whose clinical and immunologic statuses are stable.14–16 Given these findings and recommendations, it follows that the virally suppressed persons identified in the CDC report9 may have had varying levels of engagement in care.
To better understand the differences in viral suppression among persons who are engaged in infrequent care compared with those engaged in more continuous care, we examined viral suppression within and across 2 distinct groups of care recipients: those who were “engaged in care” (≥1 CD4 or VL test in the designated year but no second test that would qualify them for the NHAS retention definition) and those who were “retained in continuous care” [≥2 tests ≥3 months apart (met the NHAS definition)]. Within each of these 2 care categories, we identified differences between subpopulations. We then examined the differences in viral suppression between subpopulations across the 2 care categories (engaged in care vs. retained in continuous care). To fully evaluate the gaps in viral suppression as they pertain to frequency of care, and to assess the HHS Core Indicator definition using surveillance data, we examined viral suppression among persons who met the HHS Core Indicator definition (“HHS definition”) of retention in care over a 24-month period.
We used HIV case surveillance data reported to the National HIV Surveillance System (NHSS) through December 2012. Data were included from 19 areas (18 states and the District of Columbia) that met the following criteria: (1) the jurisdiction's laws/regulations required the reporting of all CD4 and VL results to the state/city health department, (2) laboratories that perform HIV-related testing for the areas had reported a minimum of 95% of HIV-related test results to the state/city health department, and (3) by December 31, 2012, the area had reported (to CDC) at least 95% of all CD4 and VL test results received from January 2010 through September 2012. The 18 states were California (Los Angeles County and San Francisco only), Delaware, Georgia, Hawaii, Illinois, Indiana, Iowa, Louisiana, Michigan, Minnesota, Missouri, Nebraska, New Hampshire, New York, North Dakota, South Carolina, West Virginia, and Wyoming.
For engaged in care and retained in continuous care analyses (Tables 1 and 2), data were limited to PLWH aged 13 years or older (at year-end 2009) whose infection was diagnosed by year-end 2009, who resided in the 19 areas at the time of diagnosis, and who were alive at year-end 2010. The analysis was focused on tests performed during 2010. For the HHS definition analysis (Table 3), data were limited to PLWH aged 13 years or older (at year-end 2008) whose infection was diagnosed by year-end 2008, who resided in the 19 areas at the time of diagnosis, and who were alive at year-end 2010. The analysis was based on tests performed during 2009 and 2010 (ie, 24 months). The delay between analysis year(s) (2010 or 2009–2010) and dataset year (December 2012) allowed time for reporting of diagnoses and deaths to the state and local health departments and to CDC.
- Any care: ≥1 CD4 or VL test during the evaluation period.
- Engaged in care: ≥1 CD4 or VL test during 2010 [any tests subsequent to the first, must have been within (<) 3 months or otherwise deemed ineligible for meeting the “retained in continuous care” definition].
- Retained in continuous care: ≥2 CD4 or VL tests performed ≥3 months apart during 2010.
- Retained in care, HHS Core Indicator: ≥1 CD4 or VL test in each 6-month period of the 24-month measurement period, with a minimum of 60 days between the first test date in the prior 6-month period and the last test date in the subsequent 6-month period.
- Viral suppression: VL result of ≤200 copies/mL based on the most recent VL test.
We first identified PLWH who had received “any care” during 2010 and then categorized these persons into the 2 care groups (“engaged in care” and “retained in continuous care”). Within each of the 2 care groups, we estimated prevalence ratios with confidence intervals to identify differences in percentages of persons with viral suppression between subpopulations (Table 1). We then performed chi-square tests across the 2 care groups to examine whether differences exist between the percentages of persons in each subpopulation with viral suppression who received more or less frequent clinical monitoring (Table 2).
For the HHS definition (Table 3), we identified PLWH who had “any care” during the 24-month period (2009–2010); among these persons with any care, we identified persons with ≥1 CD4 or VL test result during January through June 2009 (to be considered for care engagement in this analysis, persons must have met this criterion). Among those receiving care in the first 6 months of the 24-month measurement period, we determined the numbers and percentages of persons who met the HHS definition for retention in care. Finally, we determined the numbers and percentages of persons retained in care who were virally suppressed at their most recent test and estimated prevalence ratios with confidence intervals to identify differences between subpopulations.
Engaged in Care and Retained in Continuous Care
There were a total of 338,959 persons with HIV diagnosed by year-end 2009 and alive at year-end 2010 (PLWH) in the 19 areas (Table 1). Of these, 63.4% (214,734) had ≥1 CD4 or VL test (any care) during 2010. The percentages of persons with any care were similar (range: 60.8%–67.7%) by sex, age, race/ethnicity, and transmission category, although slightly lower percentages were found in few populations [American Indians/Alaska Natives (AI/ANs), 55.5%; Native Hawaiians/Other Pacific Islanders (NHOPIs), 57.5%; males who inject drugs, 54.6%] and a higher percentage among persons of multiple races (81.5%).
Of 214,734 persons with any care during 2010, 19.7% (42,363) were considered engaged in care while 80.3% (172,371) were retained in continuous care. Similar patterns were observed in levels of engagement by sex, race/ethnicity, and transmission category. However, percentages varied by age group, with slightly higher percentages of younger persons engaged in care and lower percentages retained in continuous care (eg, for both 13–24 and 25–34 age groups, 24.3% were engaged in care and 75.7% were retained in continuous care). For older age groups, the reverse was true (eg, for persons aged 55 years or older, 15.6% were engaged in care and 84.4% were retained in continuous care).
Viral Suppression Among Persons “Engaged in Care”
Overall, 47.7% of 42,363 persons engaged in care were virally suppressed in 2010. The percentage of females with viral suppression was 15% lower than that among males. Viral suppression increased as age increased; however, all age groups had significantly lower percentages of viral suppression compared with those aged 55 years or older. The largest percentage difference was among persons aged 13–24 years (56% lower than persons aged 55 years or older), followed by persons aged 25–34 years (40% lower). AI/ANs, blacks/African Americans (blacks), Hispanics/Latinos, and persons of multiple races were significantly less likely than whites to be virally suppressed (range: 18%–37% lower). By transmission category, all subpopulations had significantly lower percentages compared with males with infection attributed to male-to-male sexual contact (range: 13%–23% lower; Table 1).
Viral Suppression Among Persons “Retained in Continuous Care”
Overall, 73.6% of 172,371 persons retained in continuous care were virally suppressed in 2010. Females were 8% less likely than males to be virally suppressed. Viral suppression increased as age increased; however, all age groups had significantly lower percentages of viral suppression than persons aged 55 years or older. The largest difference (34% lower) was among persons aged 13–24 years. Asians were more likely to be virally suppressed than whites. AI/ANs, blacks, Hispanics/Latinos, and persons of multiple races were less likely to be virally suppressed than whites; the largest difference was among blacks (18% lower than whites), followed by persons of multiple races (14% lower). By transmission category, all subpopulations had significantly lower percentages compared with males with infection attributed to male-to-male sexual contact (range: 7%–25% lower; Table 1).
Differences in Viral Suppression Between Persons Engaged in Care and Persons Retained in Continuous Care
Persons “engaged in care,” regardless of sex, age, race/ethnicity, and transmission category, had significantly lower percentages of viral suppression than persons “retained in continuous care” (Table 2).
Retained in Care, HHS Core Indicator
There were a total of 322,297 persons with HIV diagnosed by year-end 2008 and alive at year-end 2010 (Table 3). Of these, 222,009 (68.9%) had ≥1 CD4 or VL test over the 24-month period; of these, 173,870 (78.3%) had a CD4 or VL test between January and June of 2009 and were deemed “eligible” for the HHS retention in care indicator.
Overall, 68.7% (119,510) of 173,870 eligible persons met the HHS definition for retention in care. The percentages of persons retained in care were similar by sex. By age group, lower percentages of younger persons were retained in care (60.4% for both 13–24 and 25–34 age groups) and percentages increased as age increased (76.0% for persons aged 55 years or older). By race/ethnicity, Hispanics/Latinos had slightly higher percentages of retention (76.3%), whereas AI/ANs and NHOPIs had lower percentages (57.3% and 50.0%, respectively). By transmission category, both males and females who inject drugs had slightly higher percentages (74.6% and 73.5%, respectively), as well as females with HIV attributed to other risk factors (75.4%; ie, persons infected perinatally but aged 13 years or older during the analysis period, blood transfusion recipients, or unknown risk factor).
Viral Suppression Among Persons “Retained in Care, HHS Core Indicator”
Overall, 78.2% of 119,510 persons retained in care during 2009–2010 were virally suppressed. Females were 7% less likely than males to be virally suppressed. Viral suppression increased as age increased; however, all age groups had significantly lower percentages of viral suppression than persons aged 55 years or older; the largest difference (31% lower) was among persons aged 13–24 years. Asians had a significantly higher percentage of viral suppression than whites, whereas AI/ANs, blacks, Hispanics/Latinos, and persons of multiple races had lower percentages than whites; the largest percentage difference was among blacks (16% lower), followed by persons of multiple races (13%). By transmission category, all subpopulations had significantly lower percentages compared to males with infection attributed to male-to-male sexual contact (range: 6%–26% lower; Table 3).
Engaged in Care and Retained in Continuous Care
Only two thirds of 339,959 PLWH in the 19 areas had evidence of receiving any HIV care (≥1 CD4 or VL test) during 2010. Although this percentage is higher than some previous reports,8 it is far too low. It is promising that 80% of all persons receiving any care met the “retention in continuous care” definition; however, these 172,371 persons represent only 50.9% of all PLWH in 2010.13
A recent CDC report indicated that 68.5% of PLWH who had received any care (≥1 CD4 or VL test) in 2010 had achieved viral suppression.13 The results of the current analysis show that there is a distinct difference in viral suppression between persons receiving only 1 CD4 or VL test and those who are considered retained in continuous care. A significantly higher percentage of persons with more frequent CD4 and VL monitoring had a positive treatment outcome (ie, viral suppression) than persons with less frequent monitoring. This is consistent with and complements recent findings indicating timely linkage to care and more frequent care visits among persons diagnosed with HIV were associated with faster time to viral suppression.5
Although similar patterns were seen across subpopulations in each of the 2 care categories, several subpopulations receiving less frequent care were at particular risk for virologic failure, including persons aged 13–24 and 25–34 years, as well as blacks. Not only did persons in these subpopulations have significantly lower levels of viral suppression than their counterparts receiving more frequent care but levels of viral suppression were also significantly lower than other groups who received the same frequency of care (64% lower viral suppression among persons aged 13–24 years and 40% lower in persons aged 24–35 years compared with persons aged 55 years or older; and 37% lower in blacks compared with whites). These findings are similar to other studies that found younger populations and blacks have lower levels of care, treatment, and viral suppression.4,17,18
However, the findings also re-emphasize that some subpopulations may be particularly vulnerable to falling out of care and/or treatment nonadherence.19 It is important to note, however, that treatment guidelines during the time reflected in our analysis recommended ART according to severity of disease; therefore, because young persons may have had higher CD4 counts, they may not have been offered ART.20 This may also explain some other subpopulation differences.
Our analysis also highlights populations who may be at risk not only for virologic failure but also for not receiving HIV care. The percentages of persons who received “any care” (≥1 CD4/VL in 2010) were relatively lower for AI/ANs, NHOPIs, and males who inject drugs compared with their counterparts. Without receiving care, these groups may have a lower likelihood of achieving viral suppression. The small population sizes make it more difficult to identify gaps in HIV care and treatment for AI/ANs and NHOPIs21,22; however, the results of our analysis suggest that engagement in care and treatment may be lacking for these subpopulations and more focused efforts to decrease barriers to obtaining care and treatment may be needed.
Retained in Care, HHS Core Indicator
Our analysis using the HHS definition of retention in care is the first of its kind using NHSS data. The results indicate similar patterns of viral suppression compared with our other analysis of “retained in continuous care,” despite the very different analysis, timeframe, and denominator used to calculate the percentages.
This analysis shows that persons who meet the HHS definition have high levels of viral suppression. However, few actually meet the definition. The denominator used for the HHS definition limits the analysis to persons with a CD4 or VL test in the first 6 months of the 24-month measurement period. In our analysis, these individuals represent 78.3% of all persons receiving any care during the 24-month period but only 53.9% of PLWH (data not shown).
Furthermore, persons identified as retained in care using the HHS definition represent 68.7% of the denominator population (CD4 or VL test during the first 6 months); however, these persons represent only 53.8% of persons receiving any care and 37.1% of PLWH (data not shown). Comparatively, the denominator used for the analysis of persons considered “retained in continuous care” (NHAS definition) represented 63.4% of PLWH. Also, persons retained in continuous care represented 80.3% of persons receiving any care (Table 1) and 50.9% of PLWH.13 Regarding the application of the HHS definition to surveillance data, our analysis suggests that, as a clinical monitoring tool, the HHS Core Indicator definition may suffice. However, for national monitoring of retention in care using HIV surveillance data (CD4 and VL test results), our analyses suggest that the HHS definition may underestimate the number of persons receiving care.
Although the HHS-endorsed core indicators for monitoring HIV services8 define viral suppression as that among all persons with ≥1 medical visit in a 12-month measurement period, we analyzed viral suppression among the population of persons retained in care over a 24-month measurement period as defined by the HHS Core Indicator. This was done to make it relatively comparable with the analysis of persons considered “retained in continuous care” in Table 1. The results indicated <5% difference in viral suppression between persons and very similar patterns across subpopulations when using the 2 definitions (73.6% retained in continuous care; 78.2% meeting HHS definition).
Several factors beyond frequency of CD4 and VL monitoring may influence viral suppression. Because we did not have information on ART use and adherence for this analysis, we were unable to assess adherence among persons with virologic failure. Although treatment regimens have become more robust and forgiving of the occasional nonadherer,23,24 ART adherence remains vital to achieving and maintaining viral suppression. Virologic failure is possibly indicative of nonadherence to ART; however, it is also possible that ART was not prescribed because treatment guidelines at that time recommended treatment based on stage of disease.20 Future research may benefit from comparing viral suppression among persons ever diagnosed with AIDS (ie, HIV infection, stage 3) with that among those who have not progressed to AIDS. It is also possible that regardless of the amount of care received, persons who achieve viral suppression and those who do not may be living in different social and economic environments that impact their ability to access care. Recent data suggest that frequency of care may not be the cause of virologic failure, so much as missed or canceled appointments.14 It is well-documented that social and structural factors influence the ability to access care or adhere to treatment.25,26 Therefore, reducing barriers to care is also important.
Our analyses are subject to several limitations. Retention in care and viral suppression were based on data from 19 jurisdictions; although 37 jurisdictions had regulations requiring all levels of CD4 and VL test results be reported to health departments, only 19 areas met the inclusion criteria for the analysis. The data from these 19 jurisdictions represent only 41% of persons aged 13 years or older with HIV diagnosed through year-end 2009 who were alive at year-end 2010 in the United States, and therefore, are not nationally representative. Despite this, the distribution of data by sex, race/ethnicity, age group, and transmission category for the 19 areas is comparable with that of the general population of PLWH in the United States. With continued improvements in laboratory reporting of CD4 and VL test results, future analyses will allow for more robust and representative findings. Also, this analysis included PLWH in the jurisdictions based on residence at diagnosis and does not account for migration; although national-level data processing de-duplicates cases across jurisdictions, persons may seem out-of-care or not virally suppressed if laboratory reports were missing for PLWH who moved to an area outside the 19 jurisdictions (eg, if the new jurisdiction does not require reporting of all CD4 and VL values).27,28 Finally, treatment data are not available in NHSS, so we were not able to assess the relationship between ART and viral suppression; instead, we measured viral suppression among PLWH who received care.
In this analysis, more frequent CD4 and VL monitoring was associated with higher levels of viral suppression, although younger persons and blacks continue to be at risk for virologic failure.
Although longer intervals between care visits may benefit some patients, this option may not be appropriate for all patients. Improved outcomes may be possible now that the revised treatment guidelines recommend offering ART to all persons with HIV regardless of their stage of disease.29,30 Future research should explore the relationship between CD4 and VL monitoring frequency, ART adherence, and viral suppression to monitor uptake of the revised recommendations.
1. Cohen MS, Chen YQ, McCauley M, et al.. Prevention of HIV-1 infection with early antiretroviral therapy. N Engl J Med. 2011;365:493–505.
2. Marks G, Gardner LI, Craw J, et al.. Entry and retention in medical care among HIV-diagnosed persons: a meta-analysis. AIDS. 2010;24:2665–2678.
3. Gardner EM, Daniloff E, Thrun MW, et al.. Initial linkage and subsequent retention in HIV care
for a newly diagnosed HIV-infected cohort in Denver, Colorado. J Int Assoc Provid AIDS Care. 2013;12:384–390.
4. Ulett KB, Willig JH, Lin HY, et al.. The therapeutic implications of timely linkage and early retention in HIV care
. AIDS Patient Care STDS. 2009;23:41–49.
5. Hall HI, Tang T, Westfall AO, et al.. HIV care visits and time to viral suppression, 19 U.S. jurisdictions, and implications for treatment, prevention, and the National HIV/AIDS Strategy. PLoS One. 2013;8:e84318.
6. Gardner EM, McLees MP, Steiner JF, et al.. The spectrum of engagement in HIV care and its relevance to test-and-treat strategies for prevention of HIV infection. Clin Infect Dis. 2011;52:793–800.
7. Centers for Disease Control and Prevention. Vital signs: HIV prevention through care and treatment—United States. MMWR Morb Mortal Wkly Rep. 2011;60:1618–1623.
8. Hall HI, Frazier EL, Rhodes P, et al.. Differences in human immunodeficiency virus care and treatment among subpopulations in the United States. JAMA Intern Med. 2013;173:1337–1344.
9. The White House Office of National AIDS Policy. Washington, DC: National HIV/AIDS Strategy for the United States. 2010. Available at: http://www.whitehouse.gov/administration/eop/onap/nhas/
. Accessed November 08, 2013.
10. Committee to Review Data Systems for Monitoring HIV Care. In: Volberding PA, Aidala A, Celentano D, et al.. Monitoring HIV Care in the United States: Indicators and Data Systems. Washington, DC: Institute of Medicine National Academy of Sciences; 2012.
11. Valdiserri RO, Forsyth AD, Yakovchenko V, et al.. Measuring what matters: development of standard HIV core indicators across the U.S. Department of Health and Human Services. Public Health Rep. 2013;128:354–359.
12. NQF: Measures, Reports, & Tools. Washington, DC: National Quality Forum; 2014. Available at: http://www.qualityforum.org/Measures_Reports_Tools.aspx
. Accessed August 27, 2014.
13. Centers for Disease Control and Prevention. Monitoring selected national HIV prevention and care objectives by using HIV surveillance data—United States and 6 dependent areas—2011. HIV Surveill Supplemental Rep. 2013;18. Available at: http://www.cdc.gov/hiv/library/reports/surveillance/
. Accessed November 08, 2013.
14. Buscher A, Mugavero M, Westfall AO, et al.. The association of clinical follow-up intervals in HIV-infected persons with viral suppression on subsequent viral suppression. AIDS Patient Care STDS. 2013;27:459–466.
15. Gale HB, Gitterman SR, Hoffman HJ, et al.. Is frequent CD4+ T-lymphocyte count monitoring necessary for persons with counts >=300 cells/μL and HIV-1 suppression? Clin Infect Dis. 2013;56:1340–1343.
16. Aberg JA, Gallant JE, Ghanem KG, et al.. Primary care guidelines for the management of persons infected with HIV: 2013 update by the HIV Medicine Association of the Infectious Diseases Society of America. Clin Infect Dis. 2014;58:e1–e34.
17. Mugavero MJ, Lin HY, Willig JH, et al.. Missed visits and mortality among patients establishing initial outpatient HIV treatment. Clin Infect Dis. 2009;48:248–256.
18. Yehia BR, Fleishman JA, Metlay JP, et al.. Comparing different measures of retention in outpatient HIV care. AIDS. 2012;26:1131–1139.
19. Rudy BJ, Murphy DA, Harris DR, et al.. Adolescent Trials Network for HIV/AIDS Interventions. Patient-related risks for nonadherence to antiretroviral therapy among HIV-infected youth in the United States: a study of prevalence and interactions. AIDS Patient Care STDS. 2009;23:185–194.
20. Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the use of antiretroviral agents in HIV-1–infected adults and adolescents. Dept Health Hum Serv. 2011:1–166. Available at: http://www.aidsinfo.nih.gov/ContentFiles/AdultandAdolescentGL.pdf
. Accessed April 08, 2011.
21. Centers for Disease Control and Prevention. Atlanta, GA: Improving HIV Surveillance Among American Indians and Alaska Natives in the United States. 2013. Available at: http://www.cdc.gov/hiv/pdf/policies_strategy_nhas_native_americans.pdf
. Accessed January 29, 2014.
22. Centers for Disease Control and Prevention. Atlanta, GA: Effective HIV Surveillance Among Asian Americans and Native Hawaiians and Other Pacific Islanders. 2013. Available at: http://www.cdc.gov/hiv/pdf/policies_13_238558_HIVSurveillance_NHAS_v6_508.pdf
. Accessed January 29, 2014.
23. Bangsberg DR. Less than 95% adherence to nonnucleoside reverse-transcriptase inhibitor therapy can lead to viral suppression. Clin Infect Dis. 2006;43:939–941.
24. Maggiolo F, Airoldi M, Kleinloog HD, et al.. Effect of adherence to HAART on virologic outcome and on the selection of resistance-conferring mutations in NNRTI- or PI-treated patients. HIV Clin Trials. 2007;8:282–292.
25. Aziz M, Smith KY. Challenges and successes in linking HIV-infected women to care in the United States. Clin Infect Dis. 2011;52(suppl 2):S231–S237.
26. Horstmann E, Brown J, Islam F, et al.. Retaining HIV-infected patients in care: where are we? where do we go from here? Clin Infect Dis. 2010;50:752–761.
27. Buskin SE, Kent JB, Dombrowski JC, et al.. Migration distorts surveillance estimates of engagement in care: results of public health investigations of persons who appear to be out of HIV care. Sex Transm Dis. 2014;41:35–40.
28. Miller WC, Lesko CR, Powers KA. The HIV care cascade: simple concept, complex realization. Sex Transm Dis. 2013;41:41–42.
29. Thompson MA, Aberg JA, Hoy JF, et al.. Antiretroviral treatment of adult HIV infection: 2012 recommendations of the International Antiviral Society—USA panel. JAMA. 2012;308:387–402.
30. Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the use of antiretroviral agents in HIV-1–infected adults and adolescents. Dept Health Hum Serv. 2012;1–166. Available at: http://www.aidsinfo.nih.gov/contentfiles/lvguidelines/adultandadolescentgl.pdf
. Accessed August 19, 2012.