[Diagnostic performance of κ/λ serum free light chain ratio (Freelite® assay) and IgGκ/IgGλ ratio (Hevylite® assay) as prognostic biomarkers of the evolution of immune thrombocytopenia into a chronic disease in adult patients]

Introduction: Immune thrombocytopenia (ITP) is an acquired hemorrhagic disease due to antiplatelet antibodies, that will become a chronic disease in 70% of adults. Most of chronic ITP patients display clonal restriction of antiplatelet antibodies. To date, there is no biomarker able to predict the evolution of the disease. The objective of the study is to determine whether Hevylite® and/or Freelite® assays are prognostic factors for progression to chronic ITP.

Methods: This is a retrospective, monocentric, prognostic study of a biomarker, performed using frozen samples stored in a serum library. Freelite® and a Hevylite® assays were performed on the samples collected at diagnosis for adult patients with newly diagnosed ITP at the University Hospital of Poitiers between 2014/01/01 and 2017/05/01. To predict the evolution into a chronic disease, a ROC curve analysis was performed on four variables: IgGκ, IgGκ/IgGλ ratio, IgGκ - IgGλ, and κ/λ ratio.

Results: Thirty-two patients were included and analyzed. No patient had an abnormal κ/λ ratio. Three patients had an abnormal IgGκ/IgGλ ratio. The following variables IgGκ, IgGκ/IgGλ, IgGκ - IgGλ, and κ/λ ratio were not able to predict progression to chronic ITP in our study.

Conclusion: This study did not reveal any prognostic value of the Freelite® and Hevylite® tests on the evolution of ITP into a chronic disease.