Age-related waning of in vitroInterferon-γ levels against r32kDaBCG in BCG vaccinated children

Table 1 Percent-number and mean ± SD of Stimulation-Indices in PBMC assays with BCGr32Kda protein in different categories of children.

	Scar +ve n = 45	Scar -ve n = 45	TB n = 25	P value
Mean (± SD) of positive SIs	4.9 ± 1.9^a	2.9 ± 1.17^b	2.9 ± 0.73^c	p < 0.0004^ab p < 0.0014^ac
Mean (± SD) of negative SIs	1.6 ± 0.29	1.6 ± 0.31	1.7 ± 0.20
%n with positive SI*	79	39	58
%n with negative SI*	21	61	42

Stimulation Indices (SI) < 2: negative & ≥ 2: positive in T cell assays.
Statistical analysis of the mean values of SIs was done by Student's t-test.
Chi-square test to compare number of children was done by cross tabulation method:
*Scar positive Vs. Scar negative, χ² = 10.465; p < 0.001
* Scar positive Vs. Tuberculosis, χ² = 3.630; p < 0.057