Table 2. HIV Care Continuum Metric Definitions and Associated Data Sources.

Metric	Definition	Numerator	Data Sources
HIV infected	All persons with HIV infection	Not applicable a	Seattle data from National HIV Behavioral Surveillance (percent undiagnosed) HIV case surveillance
HIV diagnosed	Persons aware of their HIV infection	Number of persons diagnosed with HIV (in or out of King County) who were residing in King County as of 12/31/2011	HIV case surveillance including investigations of persons for whom no laboratory data were reported to HIV surveillance
Linked to care	Persons who completed an HIV medical visit within 90 days after HIV diagnosis	Number of persons who had a CD4 count or viral load test result reported to HIV surveillanceb OR had a confirmed care visit with an HIV medical provider ≤ 90 days after HIV diagnosis, among persons diagnosed in 2011	HIV case and laboratory surveillance Individual case investigation
In care	Persons who had ≥ 1 HIV medical visit in 2011	Number of persons with ≥ 1 CD4 or VL report in 2011	HIV case and laboratory surveillance Population-based chart review Adjusted King County data from the Medical Monitoring Project
Retained in continuous care	Persons who had ≥2 CD4 or VL reports ≥ 90 days apart in 2011	Number of persons with ≥2 CD4 or VL reports ≥ 90 days apart in 2011	HIV case and laboratory surveillance
Prescribed ART	Persons with an active ART prescription	Number of persons prescribed ART at the time of the last HIV medical visit in 2011	Population-based chart review Adjusted King County data from the Medical Monitoring Project
Virally suppressed	Persons with a viral load <200 copies/mL	Number of persons with a viral load of <200 copies/mL at last test in 2011	HIV case and laboratory surveillance Population-based chart review Adjusted King County data from the Medical Monitoring Project

^aThe estimated number of HIV infected persons served as the denominator for all steps in the HIV care continuum.

^bExcludes results from laboratory tests ordered by PHSKC staff as part of a program designed to increase linkage to care