Adolescent, Adult, Anti-HIV Agents, Antiretroviral Therapy, Highly Active, Child, Child, Preschool, Cohort Studies, Dose-Response Relationship, Drug, Drug Administration Schedule, Drug Therapy, Combination, Female, Follow-Up Studies, HIV Infections, Humans, Infant, Male, Maximum Tolerated Dose, Retrospective Studies, Risk Assessment, Severity of Illness Index, Survival Rate, Treatment Outcome