BACKGROUND:Thrombotic thrombocytopenic purpura (TTP) is a rare but potentially fatal disorder caused by ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) deficiency. Prompt identification/exclusion of TTP can thus be facilitated by rapid ADAMTS13 testing. The most commonly utilized (enzyme-linked immunosorbent assay [ELISA]-based) assay takes several hours to perform and so does not generally permit rapid testing. OBJECTIVES:To evaluate the utility of a new automated test for ADAMTS13 activity, the HemosIL AcuStar ADAMTS13 Activity assay, based on chemiluminescence and able to be performed on an ACL AcuStar instrument within 33 minutes. PATIENTS/METHODS:This multicenter (n = 8) assessment included testing of more than 700 test samples, with similar numbers of prospective (n = 348) and retrospective (n = 385) samples. The main comparator was the Technozym ADAMTS13 Activity ELISA. We also assessed comparative performance for detection of ADAMTS13 inhibitors using a Bethesda assay. RESULTS:Overall, the chemiluminescent assay yielded similar results to the comparator ELISA, albeit with slight negative bias. ADAMTS13 inhibitor detection was also comparable, albeit with slight positive bias with the AcuStar assay. Assay precision was similar with both assays, and we also verified assay normal reference ranges. CONCLUSIONS:The HemosIL AcuStar ADAMTS13 Activity assay provided results rapidly, which were largely comparable with the Technozym ADAMTS13 Activity ELISA assay, albeit lower on average. Conversely, inhibitor levels tended to be identified at a higher level on average. Thus, the HemosIL AcuStar ADAMTS13 Activity assay provides a fast and accurate means to quantitate plasma levels of ADAMTS13 for TTP/ADAMTS13 identification/exclusion, and potentially also for other applications.

Histiocytic sarcoma (HS) is a rare and aggressive lympho-hematopoietic malignancy that represents less than 1% of all non-Hodgkin lymphomas with poor response to therapy. According to the World Health Organization classification it is defined on the basis of morphological and immune-histochemical properties of mature tissue histiocytes.1 It can occur sporadically or in association with other haematological neoplasms such low-grade lymphomas (follicular lymphoma or chronic lymphocytic leukaemia among others).2 Patients can present with either localised or disseminated disease involving organs such as the skin, central nervous system, spleen, gastrointestinal system, lymph nodes and the bone marrow. The pathogenesis of HS remains unclear and the presence of characteristic cytogenetic abnormalities such as PTEN, p14ARF and p16INK4A are currently non-contributory in the management or prognostication of the disease.3 As a result of the rarity of the disease and lack of clinical trials, treatment strategies remain a challenge due to limited therapeutic options which are largely based on case studies. We report a case of a 65-year-old woman presenting with histioctytic sarcoma, transformed from a low-grade B lymphoproliferative disorder (LPD). This case aims to highlight the heterogeneity of this disease, aggressive course and the limited treatment options available. References 1.Swerdlow SH, Campo E, Harris NL, et al., editors. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues. Lyon: IARC, 2017.2.Shao H, Xi L, Raffeld M, et al. Clonally related histiocytic/dendritic cell sarcoma and chronic lymphocytic leukemia/small lymphocytic lymphoma: a study of seven cases. Mod Pathol 2011; 24: 1421–32.3.Carrasco DR, Fenton T, Sukhdeo K, et al. The PTEN and INK4A/ARF tumor suppressors maintain myelolymphoid homeostasis and cooperate to constrain histiocytic sarcoma development in humans. Cancer Cell 2006; 9: 379–90.