Linkage to care within 6 months of diagnosis was significantly less frequent among MSM who also inject drugs and persons for whom HIV risk was not known (84% and 69%, respectively, P < 0.01), persons without health insurance or whose insurance status was unknown (86% and 70%, respectively, P < 0.01), and persons whose housing status at diagnosis was unknown (70%, P < 0.01). Retention in care for a second visit was less frequent among persons whose insurance status was not known (60%, P < 0.05). Among persons who were retained in care for a third visit 3–6 months after the second visit, a significantly lower proportion were under 30 years old and a significantly higher proportion were aged 50 years and older (72% and 90%, respectively, P = 0.02).
Of the total study population, 431 (50%) achieved viral suppression within 12 months of diagnosis (Table 2 and Fig. 1). Viral suppression was significantly lower among persons who were younger, MSM who also inject drugs, whose risk group was not reported, who were uninsured or whose insurance status was unknown, who lived in an impoverished neighborhood or whose residence was not known at diagnosis, and who were homeless or whose housing status was not known. Seventy-six percent of persons who were retained in care for at least a third clinic visit achieved viral suppression. Although the percentages of persons achieving viral suppression among those who were retained in care for up to 3 visits were higher than among the total study population, the distribution within subgroups was similar.
In our multivariate analysis, we identified several factors that were associated with an increased risk of not achieving viral suppression within 12 months of diagnosis. The factors were age younger than 40 years at diagnosis compared with persons aged 40 or older [odds ratio (OR): 1.92, 95% confidence interval (CI): 1.4 to 2.7], being homeless (OR: 2.13, 95% CI: 1.3 to 3.5), or having an unknown housing status (OR: 2.67, 95% CI: 1.4 to 5.0) compared with persons who were housed at diagnosis and having only a single medical visit (OR: 11.50, 95% CI: 7.8-17.1) or just 2 visits (OR: 3.21, 95% CI: 2.0 to 5.1) compared with 3 visits within 12 months after diagnosis.
In San Francisco, a city with widely available HIV testing, access to care, and ART at low or no cost, we found that close to 90% of newly diagnosed cases were linked to care within 6 months. Short-term retention in care was not as high; only 72% of persons had a second viral load or CD4 test in the following 3–6 months. But of those with a second test, 80% showed evidence of continued care for at least the next 3–6 months. Unfortunately, because half of the population of newly diagnosed individuals dropped out along the continuum of care, only 50% of the total population achieved viral suppression within 12 months of diagnosis. As expected, among those who remained in care for up to 12 months (i.e., retained in care for a third visit), the proportion virally suppressed was higher than in the total population.
Along this continuum of care, 2 markers of social marginalization and decreased resources—health insurance and housing status—emerged as factors associated with poor utilization of care and not achieving viral suppression. Homelessness has been consistently shown to correlate with poorer health outcomes compared with those who are stably housed.43,52–54 Unstable housing is associated with delayed care and fewer ambulatory visits in persons living with HIV.55–58 This may be from competing priorities such as food security, barriers to managing complex health conditions (such as lack of transportation and storage), and higher burden of comorbidities, including mental illness and substance use.55,59,60 When stable housing is provided as an intervention, HIV outcomes improve.35,52,61,62
Similarly, lower socioeconomic status has long been established as associated with poorer health outcomes, independent of race/ethnicity and insurance, in a variety of chronic illnesses.63–66 In the era of highly effective ART, higher socioeconomic status predicts better care utilization67 and survival.68,69 Finally, our finding that lack of insurance is associated with decreased utilization of outpatient care is also consistent with other studies,56,67,70–72 potentially accounting for increased HIV mortality among the uninsured.73 But in contrast to other studies of care utilization,33,56,67,70,71,74–76 we did not identify gender or race/ethnic differences in entry and retention in care, although the comparison may be limited given the variation in outcomes measured, populations studied, and the interaction among these variables.
The CDC recently published estimates of indicators of engagement in care using several sources of national surveillance data in which they estimate that in 2010, 77% of diagnosed persons were linked to care within 4 months of diagnosis and 51% of diagnosed persons were retained in care.13 Although our definition of timely linkage to care was more generous and our definition of ongoing engagement in care was more restrictive than those used in the national estimates, our results compare favorably to these. Though not included in our analysis, previous studies of HIV risk populations in San Francisco have found, for example, that less than 6% of infected MSM were unaware of their infection; a proportion markedly lower than the national estimates of 20%.13,77
We estimated viral suppression within 12 months of diagnosis among the total population and among persons who had a third visit within 3–6 months after the second visit. Among the persons who remained in care, our finding that 76% were virally suppressed was similar to the national estimate of 77%.13 However, among the diagnosed population, the proportion that was virally suppressed in San Francisco was substantially greater than the proportion reported nationally by CDC (50% versus 35%, respectively) although the estimates of the proportion of persons receiving ART nationwide (89%)13 was similar to what we have reported from San Francisco (83%–89%).77 This may reflect our restriction of the analysis to newly diagnosed cases in San Francisco rather than all living cases, including infected but undiagnosed persons; a separate analysis using the CDC methodology in which we used total population of living HIV cases found that 44% of the HIV-infected population in San Francisco was virally suppressed.78 The differences in the proportions of the infected population that are virally suppressed in San Francisco compared with national data may reflect the much lower proportion of undiagnosed infection among San Francisco risk populations.
Several limitations of this analysis should be considered. We defined linkage to care as an HIV-specific laboratory test within 6 months of diagnosis and retention in care as subsequent tests in the following 3–6 months. Time frames are a bit longer than recommended by the Department of Health and Human Services for CD4 and viral load testing every 3–4 four months.2 We did this to capture persons who may delay obtaining laboratory tests after a clinic visit. Relying exclusively on laboratory tests to indicate medical care can miss persons who received other types of care such as mental health and social support services. A CD4 or viral load test within 6 months of diagnosis may misclassify persons whose tests were conducted at the time of diagnosis and may not represent entry into care. This is unlikely to present a substantial misclassification bias in our study because there were only 13 cases whose CD4 or viral load tests occurred on the same day as their HIV antibody test who also did not have any subsequent tests during the observation period.
Although viral suppression is often defined as an undetectable viral load (<20–74 copies/mL, depending on the assay), some successfully treated individuals can have isolated and transient detectable low levels (usually <400 copies/mL). We defined viral suppression as a viral load of <200 copies per milliliter, consistent with the CDC, AIDS Clinical Trials Group, and Department of Health and Human Services,2,51 because some individuals experience transient elevations in viral load and variation in assays can produce detectable but low levels of virus and neither of these appear to be associated with virological failure.79–82
Our findings come from routine surveillance of HIV and as such cannot distinguish persons who moved from San Francisco from those who are not receiving care because current surveillance methods do not permit following individuals who no longer reside in San Francisco. In addition, HIV-infected San Francisco residents are reported to the San Francisco Department of Public Health but may receive some or all of their care outside of San Francisco. If so, we may have underestimated care use and viral suppression. Updates to the national HIV reporting data management system have been designed to assist in identifying persons who reside in or move to other jurisdictions and should improve estimates of care utilization through monitoring of laboratory data. Our markers of poverty, homelessness, and health insurance only pertain to the time of diagnosis, are imprecise, and do not include other key social determinants of health such as education,37,64,68,83,84 incarceration history,57,85,86 or level of social support.70,87,88 The HIV-infected population in San Francisco differs from that of many other jurisdictions where HIV infection occurs in greater frequency among women, African Americans, Latinos, IDUs, and residents of impoverished neighborhoods and as such our findings may not be representative of other communities.89
Despite these limitations, these findings provide a baseline upon which we can monitor the extent to which our population engages in care and achieves viral suppression. To reach the ultimate goal of eliminating HIV transmission through community-wide viral suppression in San Francisco, enhancing efforts toward early diagnosis, entry, and retention in care, universal provision of ART and adherence support are essential. Our article also highlights the need to prioritize the social and life style determinants of health. Although the ongoing standardized methods of HIV surveillance provide consistent data with which to monitor diagnosis and care indicators, they cannot provide a complete picture of care utilization. For this reason, we support the recommendations outlined in the Institute of Medicine report on monitoring HIV care in the United States to use multiple data sources to evaluate successes, failures, and associated factors associated with HIV diagnosis and care.90
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