Human immunodeficiency virus disease in California. Effects of the 1993 expanded case definition of the acquired immunodeficiency syndrome.

On January 1, 1993, the case definition of the acquired immunodeficiency syndrome (AIDS) in adults and adolescents used for monitoring the AIDS epidemic in California was expanded to include persons infected with the human immunodeficiency virus (HIV) with CD4 T-lymphocyte counts of less than 200 x 10(6) per liter (< 200 per mm3), pulmonary tuberculosis, recurrent pneumonia, or invasive cervical cancer. To assess the implications of this revision on AIDS case reporting in California, we compared cases reported through the end of 1994 based on 1 or more of the 4 new AIDS-defining conditions added in 1993 to cases reported based on pre-1993 AIDS-defining opportunistic infections and cancers. The 4 new conditions included in the 1993 expanded AIDS case definition accounted for a 23% increase in cumulative AIDS cases reported in California by the end of 1993, a 170% increase in the number of cases reported during 1993, and an 88% increase in the number of patients with AIDS living at the end of 1993. The number of cases reported in 1993 (19,629) was 124% more than that reported in 1992 (8,780) and 69% more than that reported in 1994 (11,587). The proportion of cases among women, injection-drug users, and African Americans also increased as a result of this change in the case definition. The expansion of the case definition may have resulted in a peak or plateau in the AIDS incidence in California because of reporting earlier in the HIV disease progression. The expanded case definition has enhanced the usefulness of AIDS surveillance data for targeting secondary prevention efforts, but more behavioral and HIV serosurveys are still needed to adequately target primary HIV prevention efforts.