Flow cytometric measurement of platelet-associated immunoglobulin in children with newly diagnosed Immune Thrombocytopenia

OBJECTIVE: To explore the clinical utility of measuring platelet-associated immunoglobulin (PAIG) at the time of diagnosis in children with immune thrombocytopenia (ITP).

METHODS: PAIG was measured by flow cytometry using fluorescent murine anti-IgG and anti-IgM. In a cohort of 88 children with ITP, the assay was performed within 15 days of diagnosis and before any treatment in 68 cases. We reviewed the results and examined the relation of isotype profile and degree of elevation to clinical manifestations and course of disease.

RESULTS: PAIG was elevated in 74%, with raised IgM being more frequent than IgG (63% vs. 44%, P = 0.04) and with isotype profile depending on symptom onset. Platelet counts at presentation were similar in all subgroups, but mucosal bleeding was less frequent in PAIG-negative patients compared to the positive groups (5.5% vs. 34%, P = 0.03). Duration of thrombocytopenia was similar in negative and positive cases, but during follow-up, significant bleeding events occurred less frequently in PAIG-negative patients (0% vs. 14%, P = 0.18).

CONCLUSION: Approximately one-quarter of children are PAIG-negative, and these children have milder bleeding tendency at diagnosis and lower morbidity during follow-up. Raised PAIG possibly may cause some degree of platelet dysfunction.