6 per 100 persons. Nationwide US estimates for the general population in 2003 show an overall ED visit rate of 38.9 visits per 100 persons, suggesting higher utilization among HIV-infected patients than in the general population [3]. Our finding that nearly one-third of patients used the ED within a 6-month interval is consistent with previous data from the pre-HAART and early HAART eras. In the pre-HAART era, 23–43% of HIV-infected persons reported utilizing the ED at least once in a 6-month period [5,28–30]. Other pre-HAART and early HAART estimates of ED utilization varied from 16 to 71% of patients

studied over periods of 3 months to 2 years [31–33]. This suggests that the benefits of HAART have not resulted in decreased use of ED services. A substantial proportion HSP inhibitor of patients (62%) reported that Crizotinib cost their most recent ED visit was because of non-HIV-related illnesses, injuries, or substance abuse. Future studies will need to examine provider-reported reasons for visitation, which may be different from patient self-report. Comparison of reason-for-visit data from patients and primary care providers may

help to identify potentially avoidable ED visits. Nevertheless, if reasons for the most recent visit are representative of reasons for all visits, HIV infection may be incidental in a significant proportion of ED visits by people with HIV disease. It is noteworthy that clinical variables, such as CD4 cell counts, HIV-1 RNA suppression and receipt of HAART were not significantly associated with any ED use. This is in contrast to data from earlier in the HIV epidemic, showing that patients with AIDS were more likely to use the ED than those with less advanced HIV disease [5]. This finding is consistent with our hypothesis that ED use in the current HAART era will be less strongly related to clinical aspects of the disease, compared with the pre-HAART era. Patients with more visits Phosphoglycerate kinase to the primary care physician had higher odds of visiting the ED. Mauskopf et al. [34], who found that patients with fewer than four visits had half the odds of making an ED visit, noted this association early in the epidemic. One interpretation

is that those with the most primary care visits are the most likely to use the ED because they are among the sickest patients. If true, illness burden may be related to comorbid conditions, given the lack of association between ED use and HIV-specific clinical variables. (The association between number of primary care visits and reason for the most recent ED visit was not significant.) All subjects in this study were engaged with a source of regular HIV care. A previous study suggested that lacking a dominant HIV provider may increase the odds of using the ED [34], and thus our results may underestimate ED use by HIV-infected patients lacking a regular source of care. However, it is notable that ED use was relatively common in this sample, despite the presence of established links with primary care providers.