The aim of this transversal study was to describe the virological and immunological features of
HIV-infected youths transferred from pediatric to adult care units since 1997 vs. the non-transferred
patients from the Madrid Cohort of HIV-infected children and adolescents in Spain.We included 106
non-transferred and 184 transferred patients under clinical follow-up in 17 public hospitals in Madrid
by the end of December 2017.Virological and immunological outcomes were compared in transferred
vs. non-transferred patients.ART drug resistance mutations and HIV-variants were analyzed in all
subjects with available resistance pol genotypes and/or genotypic resistance profiles.Among the
study cohort, 133 (72.3%) of 184 transferred and 75 (70.7%) of 106 non-transferred patients had
available resistance genotypes. Most (88.9%) of transferred hadART experience at sampling.A third
(33.3%) had had a triple-class experience.Acquired drug resistance (ADR) prevalence was significantly
higher in pretreated transferred than non-transferred patients (71.8% vs. 44%; p= 0.0009), mainly
to NRTI (72.8% vs. 31.1%; p< 0.0001) and PI (29.1% vs. 12%; p= 0.0262). HIV-1 non-B variants
were less frequent in transferred vs. non-transferred (6.9% vs. 32%; p< 0.0001). In conclusion, the
frequent resistant genotypes found in transferred youths justifies the reinforcement of HIV resistance
monitoring after the transition to avoid future therapeutic failures.