Change over time in incidence of ganciclovir resistance in patients with cytomegalovirus retinitis

BACKGROUND In the mid-1990s, the incidence of cytomegalovirus (CMV) resistance to ganciclovir was estimated to be approximately 25% by 1 year after diagnosis of retinitis in patients with acquired immunodeficiency syndrome. METHODS Two hundred fifty-seven patients with CMV retinitis were enrolled in a prospective observational study during 1993-2003 and were treated with ganciclovir. Demographic characteristics and data on CMV disease, antiretroviral therapy, and ganciclovir resistance were recorded for all patients. Human immunodeficiency virus (HIV) load and CMV load were measured for patients enrolled in 1996 or later. Kaplan-Meier and Cox proportional hazards regression methods were used to examine incidence of resistance. RESULTS The 2-year incidence of resistance was 28% among patients enrolled before 1996 and 9% among those enrolled in or after 1996 (P=.001). All cases of resistance occurred among patients with CD4+ T cell counts