Use of the Platelet Indices for Differential Diagnosis of Pediatric Immune Thrombocytopenic Purpura (ITP)

Introduction: The prognosis of pediatric immune thrombocytopenic purpura ( ITP ) has a favorable prognosis, about 80 % of ITP children will be cured in 6 months with or without therapy, the rest of patients develop to chronic ITP. However, it is difficult to predict the course of this disease at the time of diagnosis. Recent advances of automated blood cell analyzer enable to measure various blood cell parameters. Among these parameters, platelet indices such as mean platelet volume (MPV), platelet size deviation width (PDW) and platelet-large cell ratio (P-LCR) has brought about some information for thrombocytopenia. We studied the significance of such platelet indices in the differential diagnosis of immune thrombocytopenic purpura ( ITP ) and their ability to discriminate the clinical courses of ITP.

Methods: Ninety-three patients were enrolled this study at our institution from 2004 to 2006. Their ages ranged from 1 to 17 years ( media 4.3 years ). Of 93, patients were divided into two goups for analysis, according to the diagnosis of ITP. 34 were diagnosed as ITP and 59 were diagnosed various blood diseases other than ITP. In these 59 non-ITP patients, five were with thrombocytopenia ( platelet count < 100.0 × 10⁹/L ), the other without thrombocytopenia. Of 34 ITP patients, 29 were acute subtype and 5 were chronic. The Sysmex-XE2100 automated blood cell analyzer (Sysmex, Kobe, Japan) was used to measure the blood parameters, including the platelet indices.

Results: According to MPV, PDW and P-LCR, there were no significant differences between ITP patients and non-ITP. In children with ITP, there were significant inverse correlations between the platelet count and evaluated parameters, MPV (R²=0.376), PDW (R²=0.26) and P-LCR(R²=0.338). But no significant correlations were found between the platelet count and these evaluated platelet indices in non-ITP. Also, we have found all platelet indices were significantly higher in chronic ITP than in acute ITP. In particular, PDW (9.910 vs 13.080) and P-LCR (21.071 vs 33.220) showed marked differences between the two groups.

Conclusions: ITP is considered as a result of hyper-destruction of platelets. Increase of platelet count is regarded as decrease of destruction of platelets. Our data suggested that platelet indices, MPV, PDW and P-LCR showed the useful information for the degree of platelet destruction and the ability to predict the clinical courses of ITP.