A pediatric clinical and immunologic staging system for HIV infection has been developed that includes age-related definitions of immune suppression (Table 1 and Table 2) (27). Although the CD4+ T cell absolute count that identifies a specific level of immune suppression changes with age, the CD4+ T cell percentage that defines each immunologic category does not.
A change in CD4+ percentage, not number, may be a better marker of identifying disease progression in children. In infected children and adults, the CD4+ T cell count declines as HIV infection progresses, and patients with lower CD4+ T cell counts have a poorer prognosis than patients with higher counts (Table 3).
Knowledge of immune status (i.e., CD4+ T cell count and percentage) is essential when caring for HIV-infected infants and children and CD4+ T cell values should be obtained as soon as possible after a child has a positive virologic test for HIV and every three months thereafter (28, 29).
Infected infants who have a thymic defect lymphocyte immunophenotypic profile (i.e., CD4+ T cell count <1,900/mm3 and CD8+ T cell count <850/mm3) during the first six months of life have had more rapid HIV disease progression than infants who do not have this profile (30).
The CD4+ T cell count or percentage value is used in conjunction with other measurements to guide antiretroviral treatment decisions and primary prophylaxis for PCP after age one year. However, measurement of CD4+ T cell values can be associated with considerable intrapatient variation.
Even mild intercurrent illness or the receipt of vaccinations can produce a transient decrease in CD4+ T cell count and percentage; thus, CD4+ T cell values are best measured when patients are clinically stable.
Make no modification in therapy in response to a change in CD4+ T cell values until the change has been substantiated by at least a second determination, with a minimum of one week between measurements.