Thalassemia free survival after allogeneic stem cell transplantation (SCT) is about 80–90% with either matched related or unrelated donors. However, the probability of finding a HLA-compatible donor is less than 50%. We explored the use of a mismatched related (“Haplo-”) donor. All patients received two courses of pre-transplant immunosuppression therapy (PTIS) with fludarabine (Flu) and dexamethasone (Dxm) to facilitate engraftment. After two courses of PTIS, a reduced-toxicity conditioning regimen of rabbit anti-thymocyte globulin (ATG), Flu, and IV Busulfan (Bu) was given followed by T-cell replete peripheral blood progenitor cells (PBPC). GVHD prophylaxis consisted of cyclophosphamide (Cy) on days SCT +3 and +4 (Post-Cy), and on day SCT +5 tacrolimus or sirolimus was started together with a short course of mycophenolate mofetil. Thirty-one patients underwent haplo-SCT. Their median age was ten years (range, 2 to 20 years). Twenty-nine patients engrafted with 100% donor chimerism. Two of three patients with high titers of donor-specific anti-HLA antibodies suffered primary graft failure. Median time to neutrophil engraftment was 14 days (range, 11 to 18 days). Five patients developed mild to moderate, reversible veno-occlusive disease, while nine patients developed acute GVHD grade II, that quickly responded to steroid therapy. Only five patients developed limited chronic GVHD. Projected overall and event-free survival rates at two years are 95% and 94%, respectively. The median follow up time is 12 months (range; 7 to 33 months). This haplo-SCT protocol may yield excellent outcomes for thalassemia patients, and provide a treatment option for patients lacking a HLA-matched donor.

1410 Poster Board I-432 INTRODUCTION: In Thailand, the prevalences of iron deficiency anemia (IDA) and thalassemia carrier are high in the range between 20-50%. Screening of both disorders may show the similar results of low hemoglobin (Hb) and mean corpuscular volume (MCV). Therefore, additional laboratory investigations such as ferritin level, percentage of iron saturation, Hb analysis and DNA study may be required for the definite diagnosis, resulting in an increased cost. Previous studies have identified several formulas to differentiate between IDA and thalassemia carrier by using red blood cell (RBC) parameters. However, individual formula may not applicable for particular population. This study aims to establish a formula to differentiae between IDA and thalassemia carrier in school-age children in central Thailand where the prevalences of β and α thalassemia carriers are high. METHODS: After informed consent, blood was collected and tested for complete blood count (CBC), ferritin level, iron level, total iron binding capacity level, Hb analysis, and DNA study for α- thalassemia-1 (or Southeast-Asian deletion). IDA was diagnosed according to the WHO criteria. Iron deficient erythropoiesis (IDE) was defined as normal hemoglobin (Hb) level and low percentage of iron saturation or ferritin levels. Subjects diagnosed of IDA and thalassemia carrier were selected for further analysis. RESULTS: Three hundred and forty-five healthy children, aged (mean±SD) 11.3±1.7 years, were enrolled in the study. The prevalences of IDA, IDE, thalassemia trait (β, a-thalassemia-1, Hb Constant Spring and HbE trait), thalassemia disease (Hb H, β/E and Hb EE), and normal subjects were 11.6%, 38.3%, 26.1%, 2.3% and 28.7%, respectively. The red blood cell (RBC) parameters of normal, IDA, IDE, HbE trait, β trait and α trait groups were shown in the table below. The median (range) values of serum ferritin level in IDA {37.3 (92.6-162.4)}, IDE {34.3 (3-268.2)} groups were significantly different when compared to normal subjects {46.9 (13.4-232.9)}, p<0.001. However, serum ferritin level alone was not enough for the diagnosis of IDA (area under ROC curve of 0.4). Various reported formulas were used to calculate the area under ROC curve, England and Fraser, 0.78; Mentzler, 0.6; Ehsani, 0.57; Shine-Lai, 0.51; RDW/RBC, 0.88; Srivastava, 0.63; RDWI, 0.79; Green and King, 0.82 and RDW, 0.69. The RDW/RBC had the highest area under ROC curve (0.88). Further analysis of the result to differentiae IDA and thalassemia carrier showed that the RDW/RBC value of ≥3 had the sensitivity and specificity of 82.4% and 88.1%, respectively, in our studied subjects. CONCLUSION: Other than the history of iron intake and thalassemia disease in the family, RDW/RBC≥3 may be an additional test to differentiate between IDA and thalassemia carrier in Thai population. In the future, the validity of this formula in a larger scale of population is recommended. Disclosures: No relevant conflicts of interest to declare.

Patients with severe thalassemia commonly have a survival that is significantly shorter than that of the general population. Allogeneic hematopoietic stem cell transplantation (allo-SCT) is the only established treatment that is potentially curative, but it is limited by the availability of donors and the medical condition of the patient. To expand the donor pool to include haploidentical related donors, we introduced a program consisting of a pharmacologic pretransplant immune suppression phase (PTIS) and 2 courses of dexamethasone and fludarabine, followed by pretransplant conditioning with fludarabine-i.v. busulfan and post-transplant graft-versus-host disease (GVHD) prophylaxis with cyclophosphamide, tacrolimus, and mycophenolate mofetil. We transplanted 83 consecutive transfusion-dependent patients with thalassemia (median age, 12 years; range, 1 to 28 years) with a minimum follow-up of 6 months (median, 15 months; range, 7 to 53 months); the 3-year projected overall and eventfree survival is over 96%, and there have been no secondary graft failures. Of the first 31 patients, we had 2 graft failures, both of them occurring in patients with extremely high titers of anti-donor-specific HLA antibodies (anti-DSAs), but after adjusting the PTIS to include bortezomib and rituximab for patients with high titers of anti-DSAs and using pharmacologic dose guidance for busulfan, we had no graft failures in the last 52 patients. Six (7%) of 83 patients developed severe GVHD. We conclude that this is a safe and efficacious approach to allogeneic SCT in thalassemia, yielding results comparable to those available for patients with fully matched donors.

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