Background: Younger age at antiretroviral therapy (ART) initiation has been associated with smaller HIV reservoirs. We investigated whether younger age of ART initiation is associated with testing negative and weaker signal on a standard HIV diagnostic test in treated children.
Methods: At exit from a longitudinal study at 2 sites in Johannesburg, South Africa, 316 school-aged, HIV-infected children on continuous ART started at a median age of 6.3 months, were tested with standard total nucleic acid PCR used for infant diagnosis. All negative results were repeated. Simultaneous viral load (VL) and CD4 T-cell counts/percentages, along with data collected over the prior 4 years, were used in multivariable regression to predict negative PCR results and higher cycle threshold (Ct) values (weaker signal).
Results: Seven children (2.2%, 95% confidence interval: 0.6 to 3.8) in the full cohort had negative PCR results; all 7 were in a subset of 102 (6.9%, 95% confidence interval: 2.0 to 11.8) who had initiated ART at age 0-4 months and had VL <50 copies/mL at the time of PCR testing. Only one repeat tested as negative. Younger age at ART initiation, VL <50 copies/mL at time of test, sustained VL <400 copies/mL, lower CD4 T-cell counts, and ever treated with efavirenz were significant predictors of weaker signal on the diagnostic test.
Conclusions: In a small proportion of children who start ART in the first months of life and remain on continuous therapy, standard diagnostic HIV PCR tests may result as negative. Repeat testing may resolve uncertainty of diagnosis.