Figure 6. IFN-γ production by CD8 T cells is the most relevant immune parameter associated with HBsAg decline. Multivariate analyses, including binary logistic regression and decision tree algorithms, were performed to identify the immune parameters associated with different HBsAg kinetics in pegIFN-α-treated patients. (A) Spearman’s correlation matrix of the main immunological variables (TNF-α/CD4, IFN-γ/CD4, TNF-α/CD8, IFN-γ/CD8, as fold increase between weeks 24PT and baseline) and HBsAg log decline; (B) logistic regression and ROC analysis; (C) decision tree analysis on fold increase of IFN-γ production by HBV-specific CD8 T cells segregated according to the HBsAg log reduction values. AUC, area under the curve; Bas, baseline; HBsAg, hepatitis B surface antigen; IFN-γ, interferon-gamma; log₁₀, logarithm base 10; ns, not significant; pegIFN-α, pegylated IFN-alpha; PT, post-treatment; ROC, receiver operating characteristic; TNF-α, tumour necrosis factor-alpha; w, week.