Population-based metrics for the timing of HIV diagnosis, engagement in HIV care, and virologic suppression

Objective To compare population-based metrics for assessing progress toward the US National HIV/AIDS Strategy (NHAS) goals. Design Analysis of surveillance data from persons living with HIV/AIDS (PLWHA) in King County, Washington, USA, 2005-2009. Methods We examined indicators of the timing of HIV diagnosis [intertest interval, CD4 cell count at diagnosis, and AIDS ≤ 1 year of diagnosis (late diagnosis)]; linkage to initial care (CD4 or viral load report ≤3 months after diagnosis) and sustained care (a laboratory report 3-9 months after linkage); engagement in continuous care in 2009 (at least two laboratory reports ≥3 months apart); and virologic suppression. Results Thirty-two percent of persons had late HIV diagnoses, 31% of whom reported testing HIV negative in the 2 years preceding their HIV diagnoses. Linkage to sustained care, but not linkage to initial care, was significantly associated with subsequent virologic suppression. Among 6070 PLWHA in King County, 65% of those with at least one viral load reported in 2009 and 53% of all PLWHA had virologic suppression. Although only 66% of all PLWHA were engaged in continuous care, 81% were defined as engaged using the denominator proposed in the NHAS (at least one laboratory result reported in 2009 excluding persons establishing care in the second half of the year). Conclusions Proposed metrics for monitoring the HIV care continuum may not accurately measure late diagnoses or linkage to sustained care and are sensitive to assumptions about the size of the population of PLWHA. Monitoring progress toward achievement of NHAS goals will require improvements in HIV surveillance data and refinement of care metrics.