Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 0 0 2026 08 19 1 12 Mengchun Chen Clinical Laboratory, Hainan Women and Children’s Medical Center, Haikou, China Ling Hu Department of Hematology, Hainan Women and Children’s Medical Center, Haikou, China Jing Xue Clinical Laboratory, Hainan Women and Children’s Medical Center, Haikou, China Biao Liu Clinical Laboratory, Hainan Women and Children’s Medical Center, Haikou, China Meng Chang Clinical Laboratory, Hainan Women and Children’s Medical Center, Haikou, China 2025 12 26 2026 03 24 Immune thrombocytopenia (ITP), the commonest pediatric acquired bleeding disorder, involves immune dysregulation; assessing C3/C4, Ig(G/A/M), and lymphocyte subsets has diagnostic value. A retrospective study enrolled 40 children with ITP (0–18 years, meeting pediatric ITP criteria) admitted to our hospital (January 2023 to March 2025) as the ITP group, and 40 healthy children as controls. Serum IgG, IgA, IgM, C3, C4, lymphocyte subsets (CD3+, CD4+, and CD8+ T cells, CD19+ B cells, and CD16+CD56+ NK cells), autoimmune antibodies, TORCH, EBV, and CMV status were detected. Pearson correlation and receiver operating characteristic curves analyzed correlations and diagnostic efficacy of single/combined indicators, and multivariate logistic regression was used for statistical analysis. Baseline data were balanced. Compared with controls, ITP patients had higher IgG, lower IgM, C3 and C4, similar IgA; lower CD3⁺ and CD4⁺ percentages and CD4⁺:CD8⁺ ratio, higher CD8⁺ cells, similar CD16⁺/CD56⁺ and CD19⁺; and higher epstein-barr virus/cytomegalovirus and autoantibody positivity. Pearson analysis showed reduced CD4⁺, CD3⁺, C3, C4 and elevated CD8⁺, IgG correlated with lower platelet count. ROC of combined CD4⁺, CD8⁺, C3, C4, IgG gave AUC 0.967, sensitivity 92.5%, specificity 90.0%, outperforming single indices. Children with ITP have abnormal immunoglobulins, inadequate complement activation, and imbalanced lymphocyte subsets; combined detection of these aids ITP diagnosis and provides clinical basis. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/4720 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/4720/2391