Ethnic and Serologic Differences Predict Clinical Behavior and Response in Immune Thrombocytopenia (ITP).

In this study we studied the impact of race and serologic markers in clinical behavior and response in ITP patients as defined by ASH definition.

Methods: Clinical data extracted from presentation included age, sex, platelet count (PLT). All patients were negative for hepatitis B, C and HIV and patients with malignancy were excluded. Records complete with serologic markers such as ANA, anticardiolipin antibody (ACA), lupus anticoagulant (LA), cryoglobulins (CRG) were included. From 1998–2004 this yielded 160 patients; 142 of these were from US center and 18 from the Singaporean center. Information about anti-phospholipid syndrome (APS), any thrombotic episode, concurrent development of lymphomas and response to therapy was extracted from clinical records.

Results: Of the 160 patients 94 were non-Asian and 66 were Asian patients. Median age of Asian and non Asian patients was similar (38.1 Vs 39.2y). However Asians had higher female representation (92.4 vs. 70.2%, p=0.001). Presenting mean PLT count was higher in Asians (30.4X10⁹/L vs. 24.2 x10⁹/L), and were less likely to have PLT less than 10x10⁹/L (24% vs. 35%; p=0.09). There were no differences in life threatening bleeding or need for transfusion or admission. Presentation and response differences with ethnicity are depicted in Table 1. Presence of any autoimmune marker was higher in Asians (70%vs. 32%; p<0.05), ANA > 1:80, (44%vs. 28%;p<0.05) and positive cryoglobulins (15% vs. 2%, P<0.05). Presence of LA, ACA or the APS did not differ with race yet more vascular thrombosis were seen in Asians (5 vs. 1, p <0.05). Thrombosis occurred more often in presence of LA (4/14 vs. 2/146), ACA (4/23 vs. 2/137) and APS (4/23 vs. 2/137), all p<0.01. Five patients developed B-cell lymphomas, this occurred more often in patients with auto-antibodies (5/76 Vs 0/84, p=0.02). There was no difference in response to steroid treatment by race, but the presence of APS, ANA > 1:80 and LA were poor predictors of response to steroids. An inverse correlation was significant at the level 0.05 (2-tailed), with correlation coefficients being −0.197, −0.346, −0.247.

Conclusions: Racial differences occur in ITP with Asian patients having higher female preponderance, milder disease, and more auto-antibodies. Presence of such antibodies may also relate to development of B-cell NHL. ACA, APS and LA are not only predictors of thrombotic risk in ITP patients, but also predict poor response to steroid therapy.