Characteristics of studies included in review, first CD4 cell count measurement after HIV diagnosis and mortality rates prior to initiation of antiretroviral therapy (ART).

n.r. not reported.

*

Immunological and clinical eligibility criteria for ART initiation were the following:

WHO 2003 guidelines [33]: all children if WHO paediatric stage III.

WHO paediatric stage I (only when CD4 count available) or paediatric stage II:

<18 months: CD4 percentage <20%.

≥18 months: CD4 percentage <15%.

WHO 2006 guidelines [20]: all children if WHO stage 3 or 4 (there are specific rules for WHO stage 3 in case of co-infections).

WHO stage 1 or 2 (total lymphocyte counts are used in sites where CD4 values cannot be determined):

<1 year: CD4 percentage <25% or absolute CD4 cell count <1500 cells/µl.

1 to <3 years: CD4 percentage <20% or absolute CD4 cell count <750 cells/µl.

3 to <5 years: CD4 percentage <15% or absolute CD4 cell count <350 cells/µl.

≥5 years: CD4 percentage <15% or absolute CD4 cell count <200 cells/µl.

• WHO 2010 guidelines [21]: all children if <2 years or in WHO stage 3 or 4.

WHO stage 1 or 2:

2 to <5 years: CD4 percentage ≤25% or absolute CD4 cell count ≤750 cells/µl.

≥5 years: ≤350 cells/µl.

WHO 2003 guidelines [33]: all children if WHO paediatric stage III.

WHO paediatric stage I (only when CD4 count available) or paediatric stage II:

<18 months: CD4 percentage <20%.

≥18 months: CD4 percentage <15%.

WHO 2006 guidelines [20]: all children if WHO stage 3 or 4 (there are specific rules for WHO stage 3 in case of co-infections).

WHO stage 1 or 2 (total lymphocyte counts are used in sites where CD4 values cannot be determined):

<1 year: CD4 percentage <25% or absolute CD4 cell count <1500 cells/µl.

1 to <3 years: CD4 percentage <20% or absolute CD4 cell count <750 cells/µl.

3 to <5 years: CD4 percentage <15% or absolute CD4 cell count <350 cells/µl.

≥5 years: CD4 percentage <15% or absolute CD4 cell count <200 cells/µl.

• WHO 2010 guidelines [21]: all children if <2 years or in WHO stage 3 or 4.

WHO stage 1 or 2:

2 to <5 years: CD4 percentage ≤25% or absolute CD4 cell count ≤750 cells/µl.

≥5 years: ≤350 cells/µl.

**

Absolute CD4 count A, percentage CD4 P.

***

Of 162 HIV exposed children, all 24 children who were diagnosed HIV positive were included.