Incidence of opportunistic illness before and after initiation of highly active antiretroviral therapy in children

Background: Little is known about immune reconstitution inflammatory syndrome in children in the United States. Methods: LEGACY is a longitudinal cohort study of HIV-infected participants 0-24 years at enrollment during 2005 to 2007 from 22 US clinics. For this analysis, we included participants with complete medical record abstraction from birth or time of HIV diagnosis through 2006. Opportunistic illness (OI) included AIDS-defining conditions and selected HIV-related diagnoses. We calculated the incidence (#/100 patient-years) of OI diagnosed in the months pre- and postinitiation of the first highly active antiretroviral therapy (HAART) regimen which was followed by ≥1 log reduction in HIV viral load. We defined OI as immune reconstitution inflammatory syndrome if an OI incidence increased after HAART initiation. "Responders" were defined as experiencing ≥1 log decline in viral load within 6 months after HAART initiation. Results: Among 575 patients with complete chart abstraction, 524 received HAART. Of these 524 patients, 343 were responders, 181 were nonresponders and 86 experienced OI. Responders accounted for 98 of 124 (79%) of OI. Pre-HAART and post-HAART OI incidences were 43.7 and 24.4 (P = 0.003), respectively, among responders and 15.9 and 9.1 (P = 0.2), respectively, among nonresponders. Overall, OI incidences among responders and nonresponders were 33.8 and 12.3, respectively (P = 0.002). Responders were more likely than nonresponders to experience herpes simplex and herpes zoster before HAART initiation (all, P < 0.002). Conclusions: The lack of immune reconstitution inflammatory syndrome in participants initiating HAART may be due to low overall OI rates. The unexpectedly higher OI prevalence comprised mainly of herpes simplex and zoster, before HAART initiation among responders, may have motivated them to better adhere to HAART.