Table 1.
Outcome measure definitions and data sources
| Metric | Definition | Reference | Data Sources | Numerator Population | Denominator Population |
|---|---|---|---|---|---|
| Timing of HIV diagnosis | |||||
| Intertest interval | Median number of months between the last negative and the first positive HIV test | Helms, et al [2] | Surveillance case reports, testing history questionnaires, One-on-One charts. | NA | All persons newly diagnosed with HIV in King County, 2005–2009 |
| CD4 count at diagnosis | Median CD4 count at the time of HIV diagnosis | CDC [3] | First CD4 count reported to surveillance within 6 months after HIV diagnosis, One-on-One charts. | NA | |
| Late HIV diagnosis | Proportion of persons diagnosed with AIDS within one year of HIV diagnosis | CDC [4] | Surveillance case report forms, CD4 count reports | Persons reported with an AIDS diagnosis or laboratory surveillance evidence of a CD4 count <200 or CD4 percentage <14% within 12 month of HIV diagnosis date | |
| AIDS and death within one year of HIV diagnosis | Proportion of persons who were diagnosed with AIDS and died in the first year after HIV diagnosis | Death reports, death ascertainment | Persons with AIDS diagnosis and date of death <12 months after HIV diagnosis date | ||
| Linkage to HIV care | |||||
| Linkage to initial care | Proportion of persons who completed a medical visit within 3 months after HIV diagnosis | NHAS [8] | Dates of CD4 and VL results reported to surveillance | Persons with a CD4 or VL result reported ≤ 3 months after HIV diagnosis date | |
| Linkage to sustained care | Proportion of persons who linked to initial care and completed a second visit 3–9 months after linkage | NA | Persons with a CD4 or VL result reported ≤ 3 months after HIV diagnosis date and second CD4 or VL result reported ≤ 9 months after the first | All persons newly diagnosed with HIV in King County, 2007–2008 | |
| Engagement in continuous HIV care | |||||
| NHAS engagement in care | Proportion of persons with ≥ 2 medical visits ≥ 3 months apart in a calendar year | NHAS [8] and the US Health Resources and Services Administration [5] | Dates of CD4 and VL results reported to surveillance | Persons with ≥ 2 CD4 or VL results ≥ 3 months apart in 2009 (excluding those whose first CD4 or VL was reported in the second half of 2009) | Persons with ≥ 1 laboratory result in 2009 (excluding those whose first CD4 or VL was reported in the second half of 2009) |
| Population-based engagement in care | NA | Persons with ≥ 2 CD4 or VL results ≥ 3 months apart in 2009 (excluding those whose first CD4 or VL was reported in the second half of 2009) | All PLWHA presumed to reside in King County as of December 31, 2009a (excluding those whose first CD4 or VL was reported in the second half of 2009) | ||
| Virologic parameters | |||||
| Population-level virologic suppression | Proportion of persons with virologic suppression (HIV RNA <48 copies/mL) | NHAS [8] Montaner, et al [6] | VL results reported to surveillance | Persons with undetectable VL at the time of last report | Persons with ≥ 1 VL result reported in 2009 |
| Mean community viral load | Mean viral load in the population | Das, et al [7] | NA |
Empty cells indicate that the data source, numerator definition or denominator definition is the same as the completed cell above
a
All persons known to have an HIV diagnosis in King County, regardless of their place of diagnosis, who were not known to have died or relocated
NA, not applicable; CDC, U.S. Centers for Disease Control and Prevention; NHAS, U.S. National HIV/AIDS Strategy; PLWHA, persons living with HIV/AIDS; VL, viral load (HIV RNA)