Measuring the HIV Care Continuum Using Public Health Surveillance Data in the United States.

The HIV care continuum is a critical framework for situational awareness of the HIV epidemic; yet challenges to accurate enumeration of continuum components hamper continuum estimation in practice. We describe local surveillance-based estimation of the HIV continuum in the United States, reviewing common practices as recommended by the Centers for Disease Control and Prevention. Furthermore, we review some challenges and biases likely to threaten existing continuum estimates. Current estimates rely heavily on the use of CD4 cell count and HIV viral load laboratory results reported to surveillance programs as a proxy for receipt of HIV-related outpatient care. As such, continuum estimates are susceptible to bias because of incomplete laboratory reporting and imperfect sensitivity and specificity of laboratory tests as a proxy for routine HIV care. Migration of HIV-infected persons between jurisdictions also threatens the validity of continuum estimates. Data triangulation may improve but not fully alleviate biases.