目的　探讨全身炎症反应综合征 (SIRS)患儿血清补体 (C3 、C4 )活性、C反应蛋白 (CRP)水平及血小板计数变化的临床意义。方法　采用前瞻性研究方法 ,用全自动免疫比浊定量分析法和全自动血细胞计数仪测定 6 8例SIRS患儿血清C3 、C4 、CRP水平和血小板计数及其动态变化。　结果SIRS患儿首次测定的血清C3 [(4 0 6± 1 0 9)g/L]、C4 [(1 6 4± 0 89)g/L]、CRP[(5 7± 2 0 )g/L]及血小板计数 [(6 10± 140 )× 10 9/L]均显著高于非SIRS患儿组和正常对照组 (F分别为 2 77 4、10 2 0、2 2 7 0及196 2 ,P <0 0 5或 <0 0 1) ,但非SIRS患儿组和正常对照组四组参数比较差异均无显著意义 (P >0 0 5 )。动态观察发现 :SIRS组病情好转后四项参数均较好转前低 (C3 、C4 、CRP及血小板成对比较的t值分别为 14 9、8 9、14 7及 18 0 ,P <0 0 1) ;而恶化组CRP持续升高、C3 、C4 和血小板计数持续下降 ,明显不同于好转前 (C3 、C4 、CRP及血小板计数的成对比较t值分别为 8 0、4 7、2 4及 11 4,P <0 0 5或 <0 0 1)。而且病情恶化组SIRS患儿病情变化后C3 、C4 和血小板水平均低于好转组 [C3(1 5 4± 0 6 8)g/L与 (0 86± 0 6 7)g/L ,P <0 0 5 ;C4 (0 45± 0 2 3)g/L与 (0 2 5± 0 0 9)g/L ,P <0 0 5 ;血? Objective To investigate the clinical significance of serum complement (C3, C4) activity, C-reactive protein (CRP) and platelet count in children with systemic inflammatory response syndrome (SIRS). Methods A prospective study was conducted. Serum C3, C4, CRP levels and platelet counts and their dynamic changes in 68 children with SIRS were measured by automatic immunoturbidimetric assay and automatic hemocytometer. Results The serum C3 [(406 ± 1 0 9) g / L], C4 [(164 ± 0 89) g / L], CRP [(57 ± 2 0) g / L] and platelet count [(6 10 ± 140) × 10 9 / L] were significantly higher than those in non-SIRS infants and healthy controls (F = 2 77 4,10 2 0,2 ​​2 7 0 and 196 2, respectively , P <0.05 or <0.01). However, there was no significant difference in the parameters of the four groups between the non-SIRS children group and the normal control group (P> 0.05). Dynamic observation showed that the four parameters in the SIRS group improved significantly after the improvement (C, C4, CRP and platelet paired comparison t values ​​were 14 9,8 9,14 7 and 180, P <0 01 ), While CRP in worsening group continued to increase, while C3, C4 and platelet count continued to decrease, which were significantly different from those before improvement (the paired t values ​​of C3, C4, CRP and platelet count were 80,47,24 and 11 4, P <0 0 5 or <0 0 1). Moreover, the changes of C3, C4 and platelet in children with SIRS were significantly lower than those in the improvement group [C3 (154 ± 068) g / L and (866 ± 067) g / L, P < (0 45 ± 0 2 3) g / L and (0 25 ± 0 0 9) g / L, P 0 05;