Objective To investigate the associations of initial peripheral blood T lymphocyte subsets, natural killer (NK) cell level and effective platelet (PLT) recovery time with disease relapse in primary immune thrombocytopenia (ITP) children, and to construct a multifactorial predictive model for relapse risk.

Methods A total of 129 children with newly diagnosed ITP were selected and divided into relapse group (n=43) and control group (n=86) based on the results of 1-year follow-up. Initial immune indicators (T lymphocyte subsets, NK cells), PLT-related parameters, and clinical baseline data were compared between the two groups. Univariate analysis was used to screen potential risk factors, which were then incorporated into a Logistic regression model to construct a multifactorial predictive model.

Results The proportion of preceding infections in the relapse group was 39.53%, which was higher than 15.12% in the control group (P < 0.05). Before treatment, the PLT, mean platelet volume (MPV), and platelet distribution width (PDW) in the relapse group were lower than those in the control group, while the effective PLT recovery time was longer than the control group (4.92±1.43) days versus (3.36±1.20) days, P < 0.05. The levels of CD3^-CD19⁺, CD3⁺CD19^-, CD3⁺CD4⁺, CD3⁺CD8⁺, CD4⁺/CD8⁺, and NK cells in the relapse group were lower than those in the control group (P < 0.05). Multifactorial Logistic regression analysis revealed that preceding infections, prolonged effective PLT recoverytime, decreased CD3^-CD19⁺, decreased CD3⁺CD19^-, decreased CD3⁺CD4⁺, decreased CD3⁺CD8⁺, decreased CD4⁺/CD8⁺, and decreased NK cells were independent risk factors for relapse in children with ITP (P < 0.05).

Conclusion Decreased initial peripheral blood T lymphocyte subsets and NK cell levels, along with prolonged effective PLT recovery time, are associated with disease relapse in children with ITP. A multifactorial model integrating these indicators can provide a reference for clinical stratification of relapse risk.