Appendix III: Technical Notes

A Centers for Disease Control, Reproductive Health Glossary. http://www.cdc.gov/reproductivehealth/EpiGlossary/glossary.htm#EPPENDIX III: TECHNICAL NOTES

Year of Diagnosis versus Year of Report:

There are two dates associated with an HIV case, the date of HIV diagnosis and the date the case was reported to Orange County HIV/AIDS Surveillance and Monitoring Program. Most HIV/AIDS data reports utilize the report date to determine what year the case was reported. When showing case demographics in individual years, this data report will focus on the date that the case was diagnosed with HIV (unless this date is absent, in which case the AIDS diagnosis date will be used). Presenting data by year of diagnosis gives a clearer picture of the current nature of the epidemic and the demographics of the most newly infected individuals. Due to reporting delays, diagnosis data for 2018 is incomplete as cases diagnosed in 2018 will continue to be reported throughout 2018. By using the year of report, the number of cases reported each year should be relatively stable making it appropriate to compare the most current year of reporting to previous years. However, in recent years additional surveillance efforts were made to identify cases of HIV never reported to the SOA. This resulted in an increased number of cases being reported that were not reflective of an increase in the epidemic, nor were they reflective of the demographics of persons newly diagnosed.

Calculation of Rates:

 Population based rates were calculated by using population figures from California Department of Finance data

sets; the numerator represents the number of cases in a particular sub-population, period of time, or the whole population. The rate is expressed per 100,000 population.

 Percentages are calculated by dividing the number of cases in a particular group by the total number of cases

reported or diagnosed for that time period or subset. For example, the percentage of cumulative cases reported that were age 26-35 at diagnosis would be the number of cases age 26-35 at diagnosis divided by the total number of cumulated cases reported.

Data Limitations:

 Reported vs. Diagnosed cases: Data presented by demographics in this report represents the number of HIV cases diagnosed in a particular year. Caution must be taken in interpreting these data, since cases will continue to be reported which were diagnosed in previous years, so diagnosis data is never “complete.” However, it does give a more accurate picture of the current epidemic and who is testing positive today.

 Attention should be given to what the numbers represent (rates, number of cases, percentages, etc.). Please

refer to the Glossary of Terms for definitions.

 Surveillance data are revised as duplicate cases are removed at the state level. Therefore, the total numbers

presented for a particular period are subject to revision.

 The number of HIV cases among some subgroups may be small. Small numbers may appear misleadingly large when viewed as a rate. Therefore, large rates for some characteristics should be interpreted with caution.

National HIV/AIDS Strategy Methodology:

 Goal 1: Reduce the Number of New HIV Infections • Objectives 1, 2, 3: • HIV incidence (new HIV diagnosis) estimates are based on algorithms developed by the Centers for

Disease Control and Prevention (CDC) March 2018.

• Rate for Objective 2-1 is per 100 PLWH while other rates are calculated per 100,000.  Goal 2: Increase Access to Care and Optimize Health Outcomes for People Living with HIV • Objectives 4, 5, 6, 7, 8: • Laboratory data were used as a proxy for care visits; a care visit was defined as a CD4 and/or viral load

laboratory result reported to Orange County Health Care Agency (OCHCA).

• Newly diagnosed persons linked to care were defined as persons diagnosed with HIV infection during a

calendar year and received care within one months of their diagnosis (30 days).

• Homelessness in the Ryan White population is determined by the number of clients who were not stably

housed at some point during 2018.

 Goal 3: Reduce HIV-related Health Disparities • Objectives 9, 10: • Denominator for 2018 included current Orange County residents diagnosed with HIV on or before

December 31, 2018.

• Persons whose most recent viral load test result was less than 200 copies/ml during January 1-December

31 of each year were considered virally suppressed and included in the numerator of those with an “undetectable viral load”.

Suggested Citation:

 County of Orange, Health Care Agency, HIV/AIDS Surveillance and Monitoring, July 2019.