Transient viral load increases in HIV-infected children in the U.K. and Ireland: what do they mean?

OBJECTIVES: To investigate transient increases in viral load during sustained suppression in children in the UK and Ireland Collaborative HIV Paediatric Study (CHIPS).
DESIGN: Cohort of HIV-infected children from 39 centres.
METHODS: Transient viraemia was defined as > or =1 detectable viral loads (> or =50 copies/ml) between two undetectable values (<50 copies/ml) <280 days apart, during a period of sustained viral suppression (from a confirmed level of <50 copies/ml until the last undetectectable measurement before antiretroviral therapy change or until a confirmed level of >50 copies/ml).
RESULTS: Of 595 children initiating HAART without previous treatment, 347 (58%) achieved sustained suppression. Of these, 78 (23%) experienced 109 episodes of transient viraemia (median 134 copies/ml); 92 (84%) had levels of <1000 copies/ml (maximum 39,839). Transient viraemia was more common during second-line therapy (25/100 child-years [CY]) and following a previous episode (19/100 CY) compared with first-line therapy without a previous episode (11/100 CY). Rates decreased with age at HAART initiation (incidence rate ratio [IRR] 0.95 per year older; P = 0.05), but were higher in those suppressed for longer (IRR 1.63 in those suppressed for 21 year versus <1 year; P = 0.03). CD4+ and CD8+ T-cell counts were similar before and after transient viraemia. Of detectable viral loads during periods of suppression 44% were transient increases rather than virological failure: experiencing transient viraemia did not increase subsequent virological failure (P = 0.20).
CONCLUSIONS: Transient viraemia is relatively common among children on HAART, occurring more frequently in those starting HAART at younger ages, on second-line therapy and after longer suppression. It does not appear to affect CD4+ or CD8+ T-cell counts or the risk of subsequent virological failure. Natural variation, assay effects and adherence might all have a role.