Using Laboratory Surveillance Data to Estimate Engagement in Care Among Persons Living with HIV in Los Angeles County,2009

Abstract

Poor engagement in HIV care has been associated with delayed access to antiretroviral treatment and increased HIV transmission. Using viral load (VL) results from HIV laboratory surveillance data to conduct longitudinal and cross-sectional analyses, we examined linkage to care, retention in care, and their associated factors in 37,325 persons living with HIV (PLWH) in Los Angeles County (LAC). Linkage to care was considered timely if a VL test result was present ≤3 months of diagnosis. Successful retention in care was defined as having two or more VL test results ≥90 days apart during 2009. Of 6841 persons newly diagnosed with HIV in 2007–2009, 67% were linked to care within 3 months of diagnosis. Factors associated with delayed linkage to care included being African American, Latino, and Asian/Pacific Islander (adjusted hazard ratio [AHR]=0.81; 95% CI=0.75–0.87, AHR=0.83; 95% CI=0.77–0.89, AHR=0.82; 95% CI=0.71–0.94, respectively). Of the 37,325 PLWH, 52% were retained in care during 2009. Factors associated with lack of retention in care included injection drug use (adjusted prevalence ratio [APR]=0.88; 95% CI=0.84–0.93), incarceration at diagnosis (APR=0.56; 95% CI=0.51–0.61), being diagnosed in pre-highly active antiretroviral therapy (HAART) era (APR=0.94; 95% CI=0.92–0.96) or at a public facility (APR=0.97; 95% CI=0.95–1.00), age <45 years (APR=0.87; 95% CI=0.86–0.89), and having concurrent HIV/AIDS diagnoses (APR=0.94; 95% CI=0.92–0.96). This study demonstrates the value of using VL surveillance data to monitor engagement in care among PLWH, and its potential to improve linkage and retention efforts where disparities in care are observed.

Introduction

T he use of highly effective antiretroviral medications to treat HIV disease has dramatically increased the life expectancy of persons living with HIV (PLWH). Thus, ensuring the availability and accessibility of HIV care and treatment to those in need is an essential public health priority.¹ In 1990, the federal government passed the Ryan White Comprehensive AIDS Resources Emergency (CARE) Act to ensure the availability of treatment and ancillary services for PLWH. The CARE Act was reauthorized in 2009 to guarantee that those with the greatest need had continued access to life-saving care.² However, despite the availability of medical treatment, many PLWH in the United States are neither engaged in regular HIV care nor receiving antiretroviral medications.^3,4 This lack of engagement in care is disproportionately concentrated in individuals of minority status, substance users, mentally ill, homeless, and those with HIV who have not yet been diagnosed with AIDS.^4

–8 Engagement in care includes the distinct but interrelated processes of linkage to care and retention in care.^9,10 Delayed linkage to care and poor retention in HIV care have important consequences at the individual and community level as they have been associated with both delayed access to treatment and risk-reduction interventions, as well as increased chances of transmitting HIV to others due to increased plasma and genital HIV viral load levels resulting from lack of treatment.^9,11
–13

Plasma HIV viral load (VL) testing is considered one of the most important clinical markers of successful treatment because an undetectable VL indicates that a patient has achieved viral suppression.^11,12 Since the implementation of mandatory names-based HIV reporting in California in April 2006, laboratories have been required to report all VL tests to the health department. With a names-based system in place for over 5 years, the Los Angeles County Department of Public Health (LACDPH) now has a mature data system of reported VL test results to monitor initial engagement in care for newly diagnosed HIV-infected patients. To date, only a few published studies have reported on the use of VL results from HIV laboratory surveillance data to evaluate engagement in care among PLWH.^10,11,14 For example, using routine lab surveillance data of CD4 T-cell counts and VL on patients newly diagnosed with HIV infection, San Francisco investigators were able to document linkage to care in 25% more patients than by using patient or provider reports alone, and they were able to document the time it took to access care after diagnosis in those patients.¹¹ With renewed efforts to identify and reduce disparities in HIV prevention and treatment among at-risk populations in the US,¹⁵ it is critically important to use VL results as indicators of engagement in care and the effectiveness of treatment.^10,12 To our knowledge, this is the first Los Angeles-based study to use VL results from HIV lab surveillance data to assess engagement in care among PLWH. With over 42,000 reported PLWH in Los Angeles County (LAC),¹⁶ HIV lab surveillance data may offer a promising tool to identify existing disparities and to improve future engagement in care and treatment efforts.

We used VL results obtained from the Los Angeles County Department of Public Health's Enhanced HIV/AIDS Reporting System (LACDPH EHARS) to estimate engagement in care among individuals newly diagnosed with HIV between January 1, 2007 and December 31, 2009 and among PLWH (prevalent HIV cases) as of the end of 2009. First, we analyzed linkage to care by estimating the median time between HIV diagnosis and entry into primary HIV medical care during 2007–2010 and identified the socio-demographic and clinical factors associated with delayed linkage. Second, we estimated the prevalence of successful retention in care and the factors associated with lack of retention in care among all PLWH in LAC.

Methods

Procedures and participants

EHARS

EHARS is a system developed by the Centers for Disease Control and Prevention (CDC) to monitor the HIV/AIDS epidemic and to evaluate HIV prevention, care, and treatment planning.¹⁷ EHARS encompasses core HIV/AIDS surveillance data activities and projects nationwide, and provides tools to assist in the following: (1) investigation of potential HIV/AIDS cases, (2) management of current HIV/AIDS data, (3) import and export of HIV/AIDS data, (4) transfer of data to CDC, and (5) reporting and analysis.

LACDPH EHARS

HIV reporting in California is a dual-reporting system, with reporting responsibilities for both health care providers and laboratories. Laboratories are required to report all tests used to monitor HIV infection, including HIV nucleic acid detection tests (e.g., detectable and undetectable VL). Provider reports of HIV infections in LAC are collected through active and passive surveillance to identify cases of HIV and AIDS diagnosed at hospitals, clinics, private physician offices, laboratories, and community-based organizations. Active surveillance requires the LACDPH's HIV surveillance staff to routinely contact and visit sites to facilitate the completion of HIV/AIDS case reports. In LAC, about 75–80% of provider reports on HIV are collected through active surveillance activities. The remaining case reports are submitted to LACDPH EHARS passively without any contact from surveillance staff. Since April 2006, when names-based lab HIV reporting was mandated in California, over 460,000 VL laboratory tests had been reported from over 140 laboratories to LACDPH EHARS by January, 2012. The vast majority (93%) were electronic reports.

We used longitudinal and cross-sectional analyses to evaluate data on 37,325 unduplicated adults and adolescents, 13 years of age or older, who were reported to LACDPH EHARS by January 31, 2012 and were identified as living with HIV or AIDS in the county as of December 31, 2009. Because California laboratories are required to report HIV-related test results to the local health departments where the ordering provider is located, we did not have on-going VL test results for persons who sought care outside LAC after their initial HIV diagnosis. Therefore, persons who had been identified through either the intrastate de-duplication efforts or the CDC-required Routine Interstate Duplicate Review (RIDR) project as having a more recent address in a jurisdiction outside of LAC were excluded from the study population. To reduce misclassification of the outcome, “successful retention in care”, we excluded new HIV diagnoses after December 31, 2008 and all persons identified as deceased prior to December 31, 2009 through matches with the National Death Index (NDI), the national Social Security Death Master File (SSDMF), and Los Angeles County's Vital Registry (VR) records.

Measures

Socio-demographic and clinical factors

All sample characteristics were obtained from EHARS. Socio-demographics included: sex at birth (male, female), race/ethnicity (White, African American, Latino, Asian/Pacific Islander, American Indian/Alaska Native, Multi-racial), age (13–44 years, 45+ years), and country of birth (US, non-US, unknown), HIV transmission category (men who have sex with men [MSM], injection drug use [IDU], MSM/IDU, heterosexual contact, and other/unknown including blood product–related and perinatal transmission), and incarceration at diagnosis (yes vs. no). Clinical factors included year of diagnosis (pre-HAART [highly active antiretroviral therapy] vs. post-HAART defined as pre-1996 and 1996 or later), type of facility where individuals were HIV diagnosed (public vs. private), and whether individuals received a concurrent HIV/AIDS diagnoses within the same month (yes/no).

Engagement in care

In this study, we used both linkage to care and retention in care to estimate engagement in care.

Linkage to care

Linkage to care was defined as the time from initial HIV diagnosis to first VL test at or after the HIV diagnosis. As it is not uncommon for testing sites and other providers to order VL tests to diagnose HIV infection, we categorized persons who had only one VL test performed at the time of HIV diagnosis and had no subsequent VL tests as not linked to care. CD4 tests were not included in this calculation, as the mandatory reporting for CD4 tests in California began in September 2008; thus, data collected on CD4 testing are likely incomplete and do not adequately represent all persons in care at time of this report. Since names-based laboratory test reporting was not mandated until April 2006 and there was no complete VL testing information for years prior to 2006 in LACDPH EHARS, we restricted our linkage-to-care analysis to only those persons newly diagnosed with HIV in 2007–2009. To compare our findings with the National HIV/AIDS Strategy's goal of increasing the proportion of newly diagnosed patients linked to clinical care within 3 months of their HIV diagnosis to 85% by 2015,¹⁵ we defined timely linkage to care as having a VL test result present within 3 months of diagnosis. For the bivariate and multivariate analyses, linkage to care was used as a continuous variable to predict timeliness into care based on the time (days) between first HIV or AIDS diagnosis, whichever was earlier, and first entry into care.

Retention in care

One of the most commonly used methods to quantify retention in care is to set a standard for an expected number of HIV care visits in a given time period.^9,18 Because treatment guidelines recommend laboratory assessments and visits for patients every 3–6 months, time intervals have ranged between 3 and 6 months.^19,20 In this study, successful retention in care was defined as having two or more VL test results ≥90 days apart within the 2009 calendar year. We estimated retention in care for all persons who were diagnosed with HIV prior to January 1, 2009 and were living with HIV through December 31, 2009.

Data analysis

First, we examined the univariate distributions of sample characteristics with linkage to and retention in care among individuals newly diagnosed with HIV in 2007–2009, and all PLWH as of 2009 (prevalent HIV cases). We used multiple imputation methods²¹ to generate values for persons with missing data on HIV transmission category. Multiple imputation is a statistical approach in which missing values are replaced with a set of plausible values that represent the uncertainty about the true, but missing value. Second, we used survival analysis to estimate the median time (in days) for linkage to care among individuals newly diagnosed with HIV. Third, we used unadjusted and adjusted hazard ratios (HR and AHR) to predict timeliness into care by sample characteristics among new HIV diagnoses. Fourth, we used generalized linear modeling (GLM) to calculate unadjusted and adjusted prevalence ratios (PR and APR) to examine associations between retention in care and sample characteristics. In our adjusted analyses, covariates with a p value less than 0.05 were considered statistically significant predictors of our outcomes of interest. All analyses were conducted using SAS Version 9.2 (SAS Institute, Cary, North Carolina).

Results

Sample characteristics

Newly diagnosed HIV cases

The majority of newly diagnosed HIV cases were male (88%). Forty-three percent were Latino, 27% White, 24% African American, 4% Asians/Pacific Islanders, and <1% American Indian/Alaska Natives; 73% were age 13–44 years; and less than half (47%) reported being born in the US. In regard to HIV transmission mode, 80% were MSM and 11% were heterosexual. IDU and MSM/IDU each represented 4% of the sample. Seven percent were incarcerated at diagnosis while almost two-thirds (64%) received their HIV diagnosis from a private facility. Fourteen percent had concurrent diagnoses for HIV infection and AIDS (Table 1).

Table 1.

Sociodemographics, Clinical Factors, and Engagement in Care Among Individuals Newly Diagnosed with HIV in 2007–2009 and All Persons Living with HIV as of December 31, 2009 (Prevalent HIV or AIDS Cases) in Los Angeles County

Characteristics	New HIV diagnoses N (%)	New HIV diagnoses N (%) linked to care ^a	Prevalent HIV cases N (%)	Prevalent HIV cases N (%) retained in care ^b
Total	6,841 (100)	4,568 (67)	37,325 (100)	19,427 (52)
Sociodemographics
Gender
Male	5,997 (88)	4,028 (67)	32,901 (88)	17,079 (52)
Female	844 (12)	540 (64)	4,424 (12)	2,348 (53)
Race/ethnicity
White	1,819 (27)	1,312 (72)	13,009 (35)	6,448 (50)
African American	1,646 (24)	1,030 (63)	7,890 (21)	3,838 (49)
Latino	2,955 (43)	1,963 (66)	14,586 (39)	8,048 (55)
Asian/Pacific Islander	288 (4)	187 (65)	1,146 (3)	654 (57)
American Indian/Alaska Native	24 (<1)	14 (58)	173 (<1)	90 (52)
Multi-racial	109 (2)	62 (57)	521 (1)	349 (67)
Age (yrs)
13–44	5,024 (73)	3,288 (65)	17,747 (48)	8,834 (50)
45+	1,817 (27)	1,280 (70)	19,578 (52)	10,593 (54)
Country of birth
US	3,198 (47)	2,108 (66)	19,452 (52)	10,043 (52)
Non-US	1,757 (26)	1,182 (67)	10,755 (29)	6,095 (57)
Unknown	1,886 (28)	1,278 (68)	7,118 (19)	3,289 (46)
HIV risk group
MSM	5,477 (80)	3,701 (68)	28,127 (75)	14,678 (52)
IDU	300 (4)	187 (62)	2,202 (6)	1,030 (47)
MSM/IDU	268 (4)	163 (61)	2,591 (7)	1,334 (52)
Heterosexual contact	794 (11)	514 (65)	4,076 (11)	2,189 (54)
Other/unknown	3 (<1)	3 (100)	330 (<1)	195 (59)
Incarcerated at diagnosis
Yes	492 (7)	370 (75)	1,394 (4)	381 (27)
No	6,349 (93)	4,198 (66)	35,931 (96)	19,046 (53)
Clinical factors
Year diagnosed
Pre-HAART	0 (0)	N/A	11,268 (30)	5,828 (52)
Post-HAART	6,841 (100)	4,568 (67)	26,057 (70)	13,599 (52)
Type of facility tested
Public/Federal	2,455 (36)	1,717 (70)	10,808 (29)	5,368 (50)
Private	4,386 (64)	2,851 (65)	26,517 (71)	14,059 (53)
Concurrent HIV/AIDS diagnosis^c
Yes	938 (14)	797 (86)	8,391 (22)	4,191 (50)
No	5,903 (86)	3,771 (64)	28,934 (78)	15,236 (53)

MSM, men who have sex with men; IDU, injection drug use; HAART, highly active antiretroviral therapy.

Linkage to care was considered timely if within 3 months of diagnosis.

Retention in care defined as having at least two viral load (VL) tests over 90 days apart in calendar year 2009.

Concurrent HIV/AIDS diagnoses are defined as having an AIDS diagnosis and an HIV diagnosis in the same month and year.

Prevalent HIV cases

The majority of prevalent HIV cases were also among males (88%). Thirty-nine percent were Latino, 35% White, and 21% African American. Just over half (52%) were 45 years or older, and 52% reported being born in the US. The majority (75%) were MSM, 11% percent heterosexual, 7% MSM/IDU, and 6% were IDU. Four percent were incarcerated at diagnosis. Over two-thirds (70%) were diagnosed post-HAART, and 71% received their HIV diagnosis from a private facility. Twenty-two percent were reported with concurrent HIV/AIDS diagnoses (Table 1).

Linkage to care

Of the 6841 individuals newly diagnosed with HIV in our sample, 4568 or 67% were linked to care within 3 months of diagnosis (Table 1).

Overall, the median time between first HIV diagnosis and entry to care was 25 days. Individuals incarcerated at diagnosis and those with concurrent HIV/AIDS diagnoses had the lowest median time between diagnosis and entry to care (4 and 8 days, respectively). Multi-race individuals had the highest median time between diagnosis and entry to care (43 days; Table 2).

Table 2.

Median Time (Days) Between First HIV or AIDS Diagnosis and First Entry into Care, and Unadjusted and Adjusted Hazard Ratio (HR) Analyses for Predicting Timely Linkage to Care by Sociodemographics and Clinical Factors Among 6841 Individuals Newly Diagnosed with HIV in 2007–2009 in Los Angeles County

		Linked to care
Variable (reference group)	Median time (days) between first diagnosis and first entry into care (95% CI)	Unadjusted HR (95% CI)	Adjusted HR (95% CI)
Sociodemographics
Gender (male)
Male	25 (25–26)
Female	31 (29–31)	0.89 (0.83–0.97)^b	1.03 (0.87–1.22)
Race/ethnicity (white)
White	19 (18–20)
African American	29 (28–30)	0.81 (0.76–0.88)^c	0.81 (0.75–0.87)^c
Latino	27 (27–28)	0.84 (0.79–0.90)^c	0.83 (0.77–0.89)^c
Asian/PI	29 (27–31)	0.82 (0.72–0.94)^b	0.82 (0.71–0.94)^b
American Indian/Alaska Native	35 (30–45)	0.90 (0.59–1.38)	0.91 (0.59–1.41)
Multi-race	43 (34–49)	0.87 (0.71–1.07)	0.84 (0.69–1.04)
Age (45+)
45+	20 (20–21)
13–44	28 (27–28)	0.90 (0.85–0.95)^c	0.95 (0.90–1.01)
Country of birth (US)
US	28 (28–29)
Non-US	27 (26–27)	1.03 (0.96–1.09)	1.00 (0.93–1.08)
Unknown	20 (18–21)	1.01 (0.94–1.09)	0.98 (0.90–1.06)
HIV risk group (MSM)
MSM	25 (24–25)
IDU	31 (29–34)	0.91 (0.80–1.03)	0.86 (0.74–1.01)
MSM/IDU	34 (31–39)	0.92 (0.80–1.05)	0.90 (0.79–1.03)
Heterosexual contact	29 (27–31)	0.89 (0.82–0.97)^b	0.89 (0.75–1.05)
Other/unknown	12 (8–61)	1.77 (0.57–5.50)	1.90 (0.61–5.93)
Incarcerated at diagnosis (No)
No	27 (27–28)
Yes	4 (2–5)	1.20 (1.09–1.33)^c	1.22 (1.09–1.37)^c
Clinical factors
Type of facility (private)
Private	29 (29–30)
Public/Federal	20 (20–21)	1.09 (1.03–1.15)^b	1.07 (1.01–1.14)^a
Concurrent HIV/AIDS diagnoses^d (No)
No	30 (29–30)
Yes	8 (8–9)	1.69 (1.57–1.81)^c	1.68 (1.56–1.81)^c

MSM, men who have sex with men; IDU, injection drug use.

p<0.05; ^b p<0.01; ^c p<0.001.

Concurrent HIV/AIDS diagnoses are defined as having an AIDS diagnosis and an HIV diagnosis in the same month and year.

The unadjusted and adjusted hazard ratios for predicting timely linkage to care by sample characteristics are presented in Table 2. Characteristics associated with delayed linkage to care included females compared with males (HR=0.89; 95% CI=0.83–0.97; p<0.01), African Americans, Latinos, and Asian/PI compared with Whites (HR=0.81; 95% CI=0.76–0.88; p<0.001, HR=0.84; 95% CI=0.79–0.90; p<0.001; and HR=0.82; 95% CI=0.72–0.94; p<0.01, respectively), individuals age 13–44 years compared with those 45 years and older (HR=0.90; 95% CI=0.85–0.95; p<0.001), and heterosexual contact as a mode of HIV transmission compared with MSM (HR=0.89; 95% CI=0.82–0.97; p<0.05). Characteristics associated with timely linkage to care included individuals incarcerated at time of diagnosis compared with individuals not incarcerated at diagnosis (HR=1.20; 95% CI=1.09–1.33; p<0.001), individuals who obtained HIV tests at a public or federal facility compared with individuals who tested at a private facility (HR=1.09; 95% CI=1.03–1.15; p<0.001), and individuals with concurrent HIV/AIDS diagnoses compared with those without concurrent HIV/AIDS diagnoses (HR=1.69; 95% CI=1.57–1.81; p<0.001).

In our adjusted analysis, the association between delayed linkage to care and African American, Latino, and Asian/PI race remained statistically significant. Similarly, the association between timely linkage to care and incarceration at diagnosis, public testing facility, and concurrent HIV/AIDS diagnosis remained significant (Table 2).

Retention in care

Of the 37,325 individuals living with HIV as of December 31, 2009 (prevalent HIV cases), 19,427 (52%) were retained in care (Table 1).

In Table 3, we present the unadjusted and adjusted prevalence ratios for the associations between retention in care and sample characteristics for all persons living with HIV (i.e., prevalent HIV cases) in 2009. Characteristics associated with lack of retention in care in our unadjusted analyses included individuals age 13–44 years compared with those 45 and older (PR=0.92; 95% CI=0.90–0.94; p<0.001), individuals with an unknown country of birth compared with US-born individuals (PR=0.90; 95% CI=0.87–0.92; p<0.001), IDU mode of HIV transmission compared with MSM (PR=0.90; 95% CI=0.87–0.94; p<0.001), incarceration at time of diagnosis (PR=0.52; 95% CI=0.47–0.56; p<0.001), individuals who were first diagnosed at a public/federal facility compared with individuals who were diagnosed at a private facility (PR=0.94; 95% CI=0.92–0.96; p<0.001), and those with concurrent HIV/AIDS diagnoses compared with those without concurrent HIV/AIDS diagnoses (PR=0.95; 95% CI=0.93–0.97; p<0.001). Conversely, Latinos, Asians, and multi-race populations were more likely to be retained in care compared with Whites (PR=1.11; 95% CI=1.09–1.14; p<0.001; PR=1.15; 95% CI=1.09–1.21; p<0.001; and PR=1.35; 95% CI=1.27–1.44; p<0.001, respectively). Other characteristics associated with successful retention in care included individuals not born in the US compared with US-born individuals (PR=1.10; 95% CI=1.07–1.12; p<0.001), and other/unknown mode of transmission compared with MSM (PR=1.13; 95% CI=1.03–1.24; p<0.01).

Table 3.

Unadjusted and Adjusted Prevalence Ratio Analyses for Predicting Retention in Care by Sociodemographics and Clinical Factors Among 37,325 Persons Living with HIV as of December 31, 2009 in Los Angeles County

Variable (reference group)	Retained in care Unadjusted PR (95% CI)	Retained in care Adjusted PR (95% CI)
Sociodemographics
Gender (female)
Male	1.00 (0.99–1.00)	0.94 (0.89–0.99)^a
Race/ethnicity (white)
African American	0.98 (0.95–1.01)	1.02 (0.99–1.06)
Latino	1.11 (1.09–1.14)^c	1.13 (1.10–1.16)^c
Asian	1.15 (1.09–1.21)^c	1.13 (1.07–1.19)^c
American Indian/Alaska Native	1.05 (0.91–1.21)	1.08 (0.93–1.24)
Multi-race	1.35 (1.27–1.44)^c	1.37 (1.29–1.46)^c
Age (45+)
13–44	0.92 (0.90–0.94)^c	0.87 (0.86–0.89)^c
Country of birth (US)
Non-US	1.10 (1.07–1.12)^c	1.04 (1.02–1.07)^b
Unknown	0.90 (0.87–0.92)^c	0.93 (0.90–0.95)^c
HIV risk group (MSM)
IDU	0.90 (0.87–0.94)^c	0.88 (0.84–0.93)^c
MSM/IDU	0.99 (0.95–1.03)	1.01 (0.97–1.05)
Heterosexual contact	1.03 (0.99–1.06)	0.95 (0.90–1.00)
Other/unknown	1.13 (1.03–1.24)^b	1.09 (0.99–1.20)
Incarcerated at diagnosis (No)
Yes	0.52 (0.47–0.56)^c	0.56 (0.51–0.61)^c
Clinical factors
Year diagnosed (post-HAART)
Pre-HAART	0.99 (0.97–1.01)	0.94 (0.92–0.96)^c
Type of facility tested (private)
Public/federal	0.94 (0.92–0.96)^c	0.97 (0.95–1.00)^a
Concurrent HIV/AIDS diagnosis^d (No)
Yes	0.95 (0.93–0.97)^c	0.94 (0.92–0.96)^c

Note. Retention in care is defined as having at least two viral load (VL) tests over 90 days apart in calendar year 2009.

p<0.05; ^b p<0.01; ^c p<0.001.

Concurrent HIV/AIDS diagnoses are defined as having an AIDS diagnosis and an HIV diagnosis in the same month and year.

PR, prevalence ratio; MSM, men who have sex with men; IDU, injection drug use; HAART, highly active antiretroviral therapy.

After adjusting for all other covariates available in our analysis, we observed independent associations between lack of retention in care and male gender, age 44 years or younger, unknown country of birth, IDU mode of transmission, incarceration at time of report, diagnosed pre-HAART, diagnosed at a public/federal facility, and concurrent HIV/AIDS diagnoses. Additionally, we observed independent associations between successful retention in care for Latino, Asian, and multi-race categories, as well as for individuals not born in the US in our adjusted analysis (Table 3).

Discussion

In our longitudinal and cross-sectional analyses of 37,325 unduplicated adults and adolescents, we used VL test results to estimate both linkage to care and retention in care among PLWH in LAC. Overall, 67% of individuals newly diagnosed with HIV in 2007–2009 were linked to care within 3 months of diagnosis, and 52% of all PLWH were retained in care during the 2009 calendar year. In light of the recent National HIV/AIDS Strategy, which aims to increase linkage to care within 3 months to 85% and retention in care to 80% by 2015,¹⁵ these findings suggest that both linkage to and retention in care are suboptimal in LAC. These findings also demonstrate the critical role of HIV surveillance data for monitoring progress in engagement in care at the population level.²²

We estimated that one-third of newly diagnosed individuals in this study were not linked to care in a timely manner. As advances in HIV treatment are extending the length and quality of life for PLWH, understanding patterns of linkage to care is crucial for developing targeted interventions, and improving mechanisms for immediately engaging individuals in continuous and coordinated quality care when they learn they are HIV infected.^13,15 Sample characteristics associated with delayed linkage to care included being female, African American, Latino, Asian/PI, 13–44 years of age, and heterosexual contact, consistent with a number of other US-based studies that have also associated these factors with delayed linkage to care.^{4,5,23

–26} It is critical that future HIV engagement in care interventions in LAC target these high-risk populations to reduce disparities in linkage-to-care outcomes.

Just over half (52%) of our sample met our definition for successful retention in care (two or more VL test results ≥90 days apart within a year). This is similar to findings in other studies where retention in care ranged from 44% to 52%.^27,28 Since retention in HIV care is crucial to maximizing positive patient outcomes, greater efforts are needed to develop programs for retaining patients in care, especially among those populations with a history of inconsistent use of outpatient HIV care. Sample characteristics associated with lack of retention in care included being male, between the ages of 13–44 years, unknown country of birth, IDU mode of HIV transmission, incarceration at diagnosis, testing at a public/federal facility, and concurrent HIV/AIDS diagnosis. Interestingly, we found that individuals diagnosed during incarceration had a higher rate of entry into care than those not incarcerated at diagnosis, but were less likely to be retained in care. This finding supports an expansion of efforts to engage incarcerated persons into care after they return to the community. Additionally, we found that Latinos were more likely than Whites to be successfully retained in care. This finding is contrary to many linkage and retention-in-care studies that have traditionally shown disparities for Latinos in HIV care.^4,10,23,24 However, a recent study among individuals diagnosed with HIV in Philadelphia found that Latinos had a higher odds of linking to care in a timely manner than Whites.¹³ Future studies on the Latino population are needed to better understand this outcome, especially in LAC where a large proportion of the HIV/AIDS cases are among Latinos.

There are limitations to our study that should be acknowledged. The measurements of entry into care and retention in care were based on reported dates of VL testing from either the provider report or laboratory test reports. Thus, their accuracy depends on the completeness of laboratory test reports. As of January 2012 when this analysis was conducted, we had imported all VL test results in 2007–2010 that match to a case report in EHARS. Nevertheless, these measurements may have underestimated persons' visits for HIV care and the proportion of PLWH who were successfully retained in care. For example, a person might have paid a visit to a medical facility for HIV care and treatment but not received VL testing. Furthermore, the study did not include persons who had been diagnosed with an HIV infection, perhaps through anonymous testing, but had not yet been reported to the LACDPH EHARS system. Finally, our engagement in care measurements may not account for the VL tests of HIV individuals who sought care from a provider outside of LAC. Although we have included from the statewide EHARS database the VL tests reported by the public health officials in other counties that match to the individuals with an HIV diagnosis in LAC, our study may potentially underestimate the number of persons who were actually engaged in HIV care.

Conclusions

This study demonstrates the usefulness of using VL surveillance data to help large metropolitan public health departments monitor important national health goals, such as reducing the time between HIV diagnosis and entry into primary HIV medical care, as well as increasing retention in care among HIV-infected persons. Our findings also corroborate findings from other studies using HIV/AIDS laboratory surveillance data.^10,11,23 In addition, VL surveillance data may serve as an important performance measure for HIV testing and care programs under the auspices of public health departments, as well as for community-based prevention programs.¹⁰ With the growing emphasis on “treatment as prevention” and “test and treat” strategies to reduce the impact of the HIV epidemic in the US,^18,29,30 it will be increasingly important to make use of existing data systems, such as EHARS, to monitor whether improvements in linkage to care and retention in care are tracking with hypothesized reductions in HIV transmission at the population level.³¹ Additionally, when racial/ethnic or other disparities in linkage and retention in care outcomes are observed, public health data systems such as EHARS should be used to better guide the allocation of resources and reduce critical engagement-in-care disparities recognized in the National HIV/AIDS Strategy.²²

Footnotes

Acknowledgments

The authors would like to thank Chun-Mai M. Kuo, Ying Ou, and Emmanuel Mendoza of the HIV Epidemiology Program, Los Angeles County Department of Public Health for their assistance with data management. We also thank Latonya Taylor and her staff for the support with data collection.

Author Disclosure Statement

The data collection, analyses, and manuscript preparation were supported by the Centers for Disease Control and Prevention's HIV Surveillance Grant (NCA U62PS001045), the California Department of Public Health Master Agreement for HIV Surveillance (LAC Office of AIDS Programs and Policy MOU number 10-95267), and California HIV/AIDS Research Program (CH05-DREW-616, CH05-LAC-617).

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