Background:  ART improves survival among HIV⁺ persons and reduces HIV transmission. But only persons receiving HIV medical care can be prescribed ART and achieve viral suppression. Determining the number of HIV⁺ adults receiving medical care is critical to inform our efforts to improve ART uptake, but there are no nationally representative estimates of the size of the in-care population or the number of HIV⁺ persons on ART and virally suppressed.

Methods:  The Medical Monitoring Project (MMP) conducts clinical surveillance among HIV⁺ adults receiving medical care in 23 cities, states, and territories in the US. Using a 3-stage design, MMP uses probability-proportional-to-size methods to first select states or territories, followed by facilities that provide HIV medical care, and HIV⁺ adults seen at these facilities. This sampling design allows us to estimate the size of HIV⁺ population receiving medical care in the US between January and April 2009. Using in-person interviews and linked medical record abstractions, we describe the characteristics and experiences of the in-care population. Results are weighted for sampling probability and to adjust for patient non-response.

Results:  We estimate that 421,186 (95%CI 379,567 to 462,805) HIV⁺ adults were receiving HIV medical care January through April 2009 in the US, or 44% of the estimated 941,950 persons diagnosed and living with HIV infection. Of those in care, 373,591 (88.7%; 95%CI 86.9 to 90.5) persons were prescribed ART in the past 12 months and the most recent viral load for 287,670 (70.9%; 95%CI 67.7 to 74.1) persons in care was ≤200 copies/mL. By race/ethnicity, blacks were less likely to be prescribed ART (p <0.001) or achieve viral suppression (p <0.001) than whites. In addition, women were less likely to be prescribed ART (p <0.001) or achieve viral suppression (p <0.0001) than men.

Conclusions:  Fewer than half of all persons diagnosed and living with HIV infection in the US were receiving medical care in January through April 2009. While most of those in care were prescribed ART and achieved viral suppression, there were significant disparities by race and gender. Increasing the number of HIV⁺ persons in care is critical to reduce HIV-associated mortality and reduce transmission. Among those in care, disparities in HIV treatment outcomes need to be addressed.