Migration Distorts Surveillance Estimates of Engagement in Care: Results of Public Health Investigations of Persons Who Appear to Be out of HIV Care

Background: Prevention and clinical efforts are increasingly focused on improving the HIV care cascade, the sequential steps from diagnosis to engagement in care and viral suppression. Monitoring of this cascade is largely dependent on HIV laboratory surveillance data. However, little is known about the completeness of these data or the true care status of individuals for whom no data are reported.

Methods: We investigated people presumed to be living with HIV/AIDS in King County, WA, who had no laboratory results reported to HIV surveillance for at least 1 year between 2006 and 2010. We determined whether each person had relocated, died, or remained in the county.

Results: Of 7379 HIV-infected people presumed living in King County, 2545 (35%) had 1 or more 12-month gap in laboratory reporting. Among these individuals, 47% had relocated, 7% died, and 38% remained in King County; we were unable to determine the status of 8%. Of individuals remaining in the area, 91% had evidence of returning to or being in HIV care. Case investigations reduced the proportion of individuals thought to be out of care in 2011 from 27% to 16%.

Conclusions: Investigations of individuals without laboratory results reported to HIV surveillance identified large numbers of people who are no longer living in the area. Our findings suggest that current estimates of the HIV care cascade may be too pessimistic and that individual case investigations are required to accurately define the size and composition of the population of people living with HIV in local areas.