HIV viral load testing has recently become available to HIV infected patients outside of research protocols. The interpretation of viral load measurements, the best laboratory technique for their determination and the frequency with which the test should be performed is the focus of active research in the pediatric population. We report our initial experience with viral load measurements in a cohort of HIV infected children.

Methods: This retrospective cohort study describes the results of viral load analysis completed to date in HIV infected children followed at the Hospital for Sick Children, a tertiary care facility. Plasma was obtained from heparinized samples of blood taken during routine clinic visits commencing in December 1995 and stored at -70°C for subsequent analysis. Viral load determinations were performed using the NASBA assay (Organon Teknica). Mean levels were determined and compared based on mode of infection. Where possible testing was performed before and after changes in antiretroviral therapy.

Results: Results are available for 58 children, of whom 65% were perinatally infected (mean age 5.7 years). Of the remaining transfusion infected patients, 53% were hemophiliacs. The route of infection is unknown in one patient. The mean age for the non-hemophiliac and hemophiliac transfusion infected patients were 12.6 and 13.9 years respectively. There was a significant difference in initial viral loads between the perinatally infected and hemophiliac transfusion recipients (4.97 vs 3.5 log10, p<.01). Data available for 17 of the perinatally infected children and 10 of the transfusion recipients revealed initial mean decreases in viral load after addition of 3TC of 0.98 and 1.5 log10 respectively. Overall, data is available for 27 of the patients before and after adding 3TC to their antiretroviral regimen. Of these, 59% had a reduction of viral load of at least 0.5 log10 with a mean reduction of 1.19 log10.

Discussion: This preliminary data suggests that baseline viral loads are relatively high in this pediatric HIV infected cohort, with significantly higher values in the perinatally infected group. We have also demonstrated a substantial decrease in viral load after the addition of new antiretroviral agents in the majority of these children. The clinical relevance of these changes and the ways in which viral load testing will best be used in the ongoing care of HIV infected children has yet to be determined.