Clinical And Basic Research Of Immune Thrombocytopenia In Children

Objectives1.To assess the effect of antinuclear antibody(ANA)titer and its variation on outcomes of childhood immune thrombocytopenia(ITP).2.To assess the efficacy and safety of hydroxychloroquine in children with chronic ITP.And to analyze the effect of ANA on the efficacy of hydroxychloroquine.3.To assess the level of platelet apoptosis and autophagy in children with ITP.And to explore the effect of hydroxychloroquine on platelet apoptosis.Methods1.We conducted a single-center retrospective cohort study of children with ITP at a tertiary general hospital in China from January 2013 to January 2022.A generalized estimating equation model was used to assess the association between repeated ANA titer measurements and platelet counts.Cox proportional hazards regression models adjusted for confounding factors were used to assess the association between ANA titer and AID development.2.We collected data from children diagnosed with chronic ITP based on the cohort in the first section of this study.Mixed effects models were used to assess the effect of hydroxychloroquine on platelet count.Side effects associated with hydroxychloroquine were also summarized.3.Autophagy and apoptosis markers,including mitochondrial inner membrane potentials and phosphatidylserine(PS)exposure,were examined using flow cytometry.Results1.A total of 324 children with ITP were included in this study,with a median followup time of 25 months(maximum 160 months).39.2%of patients in this cohort had ANA in a titer of≥ 1:160.Results from a generalized estimating equation model revealed that patients with higher ANA titers had lower platelet counts at onset but higher recovery rates of the platelet count at follow-up times.Results from Cox regression models adjusted for potential confounders revealed that patients whose ANA titers were≥ 1:160 were more likely to develop to autoimmune disease than those whose ANA titers were<1:160(hazard ratio,3.33;95%CI,1.61 to 6.86),and the risk of AID development increased with the rise of ANA titers(P value for trend<0.001).2.A total of 191 children with chronic ITP were included in this study.61 patients had used hydroxychloroquine during the clinical course.Results from a mixed effects model revealed that hydroxychloroquine had effect on increasing platelet counts in children with chronic ITP(mean difference:22.09×109/L;95%CI:5.14～39.05).11.5%(7/61)of patients experienced side effects associated with hydroxychloroquine.3.A total of 12 ITP children and 12 healthy children were included in this study.The level of platelet autophagy in children with ITP was not significantly different from in healthy controls.The proportion of platelets with mitochondrial membrane depolarization in children with ITP tended to be higher than in healthy controls(mean:8.89%vs.3.49%;P=0.006),while the proportion of platelets with PS exposure in children with ITP were not significantly different from that of controls(mean:13.78%vs.10.60%;P=0.33).Platelet apoptosis was not significantly affected by hydroxychloroquine.And the level of platelet apoptosis was not different in ITP children between the ANA positive group and ANA negative group.Conclusions1.Among children with ITP,the ANA titer was negatively correlated with platelet counts at onset but positively correlated with the recovery rate of subsequent platelet counts.The risk of AID development increased with the rise of ANA titers.2.Hydroxychloroquine had effect on increasing platelet counts in children with chronic ITP.But side effects associated with hydroxychloroquine need to be monitored regularly.3.In ITP children,the level of platelet autophagy was not different from healthy controls,but the level of platelet apoptosis may increase.Hydroxychloroquine inhibited platelet autophagy but had no significant effect on platelet apoptosis.Platelet apoptosis was not significantly correlated with ANA in children with ITP.