At the end of June each year, AIDS cases reported during the preceding 120 months are aggregated into ten 12-month periods and 10 “survival” weights are applied to the 10 AIDS case counts. The summary count, which results from this computational formula, is the estimated number of persons living with AIDS in the EMA or state for purposes of the Ryan White CARE Act funding allocations. The survival weights are updated by CDC every two years according to methods specified in the Act (the weights were most recently updated in July 2001).

The legislative authority for the method of estimating the number of persons living with AIDS under Title I is Section 2603(a)(3)(c) of the Ryan White CARE act. The legislative authority for the Title II estimation of the number of persons living with AIDS is Section 2618(2)(d). The same set of survival weights is used for both Title I and Title II. The current weights are:

Year 1 — .12
Year 2 — .22
Year 3 — .32
Year 4 — .43
Year 5 — .57
Year 6 — .68
Year 7 — .76
Year 8 — .80
Year 9 — .85
Year 10 — .89

For each 12-month reporting period, the proportion of persons reported with AIDS and known to be alive is computed as follows:

(cases minus deaths)/cases

This proportion is the weight for the 12-month period.

These weights will be updated in July 2003, as required by the CARE act, by using the AIDS cases reported through June 30, 2003.

Details for the Three Methods of Estimating the Number of Persons Living with AIDS

Method I — Ryan White CARE act formula
The counts of reported AIDS cases for the last 120 months are aggregated into ten 12-month periods. The first year (i.e., earliest) count is multiplied by .12. The second year count is multiplied by .22, and so on for all 10 counts. The total of these 10 weighted counts is the estimated number of people living with AIDS for a given state or EMA. The estimates from this method are based on AIDS surveillance data reported to CDC through June 2001.

Method II — Number of Persons Reported to be Living with AIDS
For each state or EMA, the number of persons reported with AIDS with vital status “alive” as of June 30, 2001 is calculated. (See HIV/AIDS Surveillance Report, 2001, 13[No.1]:Table 1). Persons whose vital status is unknown are excluded, as well as those whose residence is unknown. This total count is the estimated number of people living with AIDS.

Method III — Adjustments for Reporting Delays
Estimated AIDS data are adjusted for reporting delays by a maximum likelihood statistical procedure; differences in reporting delays for geographic area, racial/ethnic, age, sex, and vital status and exposure categories are taken into account, but it is assumed that reporting delays within these groups have not changed over time (Statistics in Medicine 1998;17: 143-54 and Lecture Notes in Biomathematics 1989;83:58-88). Two maximum likelihood procedures are performed—for delays in reporting AIDS cases and for delays in reporting AIDS deaths. On the basis of the results of these procedures, each AIDS case is then assigned an AIDS incidence adjustment weight and an AIDS death adjustment weight. The point estimate of the number of persons living with AIDS is derived by subtracting the estimated cumulative number of deaths of persons with AIDS from the estimated cumulative number of persons diagnosed with AIDS. The estimates from this method are based on AIDS surveillance data reported to CDC through December 31, 2001, and include cases diagnosed and deaths occurring through June 2001. Estimated AIDS cases and estimated AIDS deaths are adjusted for reporting delays, but not for incomplete reporting. Methods used for AIDS surveillance are described in the HIV/ AIDS Surveillance Reports available at www.cdc.gov/hiv/topics/surveillance/resources/reports/index.htm.