Recombinant ADAMTS13 for Immune Thrombotic Thrombocytopenic Purpura.

In patients with immune thrombotic thrombocytopenic purpura (iTTP), autoantibodies against the metalloprotease ADAMTS13 lead to catastrophic microvascular thrombosis. However, the potential benefits of recombinant human ADAMTS13 (rADAMTS13) in patients with iTTP remain unknown. Here, we report the clinical use of rADAMTS13, which resulted in the rapid suppression of disease activity and complete recovery in a critically ill patient whose condition had proved to be refractory to all available treatments. We also show that rADAMTS13 causes immune complex formation, which saturates the autoantibody and may promote its clearance. Our data support the role of rADAMTS13 as a novel adjunctive therapy in patients with iTTP.

Emergency transfusion with whole blood versus packed red blood cells: A study of 1400 patients.

BACKGROUND: Low-titer group O whole blood (LTOWB) is increasingly used for emergency transfusion. We studied whether initial release of LTOWB compared with packed red blood cells (pRBCs) reduced overall blood requirements for patients needing emergency transfusion. Secondary outcomes examined included survival and non-lethal adverse clinical outcomes. STUDY DESIGN AND METHODS: A retrospective, single-center, before-versus-after study compared patients transfused with emergency-release, uncrossmatched pRBC followed by component therapy (2016-2019) versus patients transfused with emergency-release, uncrossmatched LTOWB followed by component therapy (2019-2022). RESULTS: Outcomes were available for 602 patients in the pRBC group versus 749 in the whole blood group. The two groups were similar for age, sex, race, estimated blood volume, ABO blood groups, and underlying diagnosis. Use of LTOWB was associated with increased blood product use at 24 h (4.0 (2.0-12.0) in pRBC group versus 6.5 (4.2-12.7) in LTOWB group, p < .0001) and at 7 days (5.5 (3.0-13.0) in pRBC group versus 7.3 (4.3-14.3) in LTOWB group, p < .0001). Initial use of LTOWB was not associated with improved 24 h or 30 day survival nor lower incidence of non-lethal adverse clinical outcomes compared with pRBC. DISCUSSION: Our study showed a statistically significant increase in total blood use and blood acquisition costs for patients receiving initial emergency transfusion with LTOWB compared with pRBC. The initial use of LTOWB offered no advantage over component therapy for 30 day survival or selected non-lethal adverse outcomes.

Retrospective analysis of outcomes in patients with acute hypertriglyceridemic pancreatitis treated without therapeutic plasma exchange.

BACKGROUND: Therapeutic plasma exchange (TPE) is often used to decrease serum triglyceride levels in hypertriglyceridemic pancreatitis (HTGP), although there is a lack of high-quality data directly attributing improved clinical outcomes to TPE. There are currently no large studies evaluating the treatment of HTGP without TPE. STUDY DESIGN AND METHODS: This study retrospectively analyzes clinical and laboratory outcomes of 115 encounters at Massachusetts General Hospital (MGH) wherein a HTGP patient was treated without TPE and compares these outcomes to those of HTGP patients in the literature treated with TPE. RESULTS: After management without TPE, the median reduction in serum triglycerides was 48% (IQR 29%-63%) on day one and 74% (IQR 60%-84%) on day two in 115 episodes of acute HTGP. The reductions were comparable to those reported in several large published case series after a course of TPE (65.8% to 81% reduction). In 25 episodes among 24 patients, treatment included admission to an intensive care unit. There was no significant difference in mortality or rates of local complication, mechanical ventilation, or use of vasoactive medication or renal replacement therapy between this ICU subset and published cohorts (all P > .05). CONCLUSIONS: HTGP patients who do not receive TPE do not experience inferior outcomes compared to patients in the literature treated with TPE. The added value of TPE in HTGP, if any exists, needs to be demonstrated in controlled trials.

Deaths and complications associated with the management of acute immune thrombotic thrombocytopenic purpura.

BACKGROUND: The introduction of therapeutic plasma exchange (TPE) dramatically decreased mortality in patients with immune thrombotic thrombocytopenic purpura (iTTP). However, there are few modern descriptions of residual causes of death from iTTP and complications associated with TPE. STUDY DESIGN AND METHODS: This was a retrospective study in a multi-institutional cohort of 109 patients with iTTP between 2004 and 2017. Complications of TPE were analyzed in a subset of this cohort (74 patients representing 101 treatment courses). RESULTS: Death occurred in 8 of 109 patients (7.3%) and in 8 of 219 captured episodes of acute iTTP (mortality rate per episode: 3.7%). Neither the number of TPE treatments nor length of hospitalization predicted mortality. The majority of deaths (5/8) were associated with delay in the diagnosis of iTTP or initiation of TPE or presentation to the hospital in a moribund state. A subset of patients (N = 74) was analyzed for TPE-related complications. Most patients (56/74; 76%) had at least one minor or major complication of TPE. Seven of 101 (6.9%) discrete treatment courses were associated with one or more severe complications, including anaphylaxis and line-associated infections and thrombosis. Overall, the most frequent adverse events were mild allergic (urticarial) transfusion reactions, which affected 34 of 101 (34%) treatment courses. One patient died from a TPE-related complication, line-associated bacteremia. CONCLUSION: Early identification of patients with iTTP and the rapid initiation of TPE are paramount in preventing mortality. While TPE was associated with a high rate of adverse events, the vast majority were treatable and TPE-related mortality is low.

Utilizing a PLASMIC score-based approach in the management of suspected immune thrombotic thrombocytopenic purpura: a cost minimization analysis within the Harvard TMA Research Collaborative.

The PLASMIC score is a recently described clinical scoring algorithm that rapidly assesses the probability of severe ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) deficiency among patients presenting with microangiopathic haemolytic anaemia. Using a large multi-institutional cohort, we explored whether an approach utilizing the PLASMIC score to risk-stratify patients with suspected immune thrombotic thrombocytopenic purpura (iTTP) could lead to significant cost savings. Our consortium consists of institutions with an unrestricted approach to ADAMTS13 testing (Group A) and those that require pre-approval by the transfusion medicine service (Group B). Institutions in Group A tested more patients than those in Group B (P < 0·001) but did not identify more cases of iTTP (P = 0·29) or have lower iTTP-related mortality (P = 0·84). Decision tree cost analysis showed that applying a PLASMIC score-based strategy to screen patients for ADAMTS13 testing in Group A would have reduced costs by approximately 27% over the 12-year period of our study compared to the current approach. Savings were primarily driven by a reduction in unnecessary therapeutic plasma exchanges, but lower utilization of ADAMTS13 testing and subspecialty consultations also contributed. Our data indicate that using the PLASMIC score to guide ADAMTS13 testing and the management of patients with suspected iTTP could be associated with significant cost savings.

Red blood cell alloantibodies are associated with increased alloimmunization against human leukocyte antigens.

BACKGROUND: Alloantibodies recognizing human leukocyte antigens (HLA) can cause immune-mediated refractoriness to platelet transfusion. An association between HLA alloimmunization and red blood cell (RBC) alloimmunization has been suggested but remains uncertain. STUDY DESIGN AND METHODS: We tested for HLA alloantibodies in 660 patients with and without RBC alloantibodies. Calculated panel reactive antibody (cPRA) values were determined for HLA alloimmunized patients. Current and historical diagnoses and blood product exposure were catalogued. Variables associated with high-level HLA alloimmunization (cPRA ≥ 90%) were evaluated. RESULTS: The cohort included 366 women and 294 men with median age of 66 years (interquartile range [IQR], 53-76). The number of patients with and without RBC alloantibodies was 447 and 213, respectively. Among patients with and without RBC alloantibodies, 20.6% and 8.5% had a cPRA ≥ 90%, respectively (p < 0.0001). In univariate analyses of men and nulliparous women and previously pregnant women, the median number of RBC alloantibodies was significantly higher in patients with a cPRA ≥ 90% (p < 0.0001). The number of RBC alloantibodies remained an independent predictor of a cPRA ≥ 90% in multivariate analysis (odds ratio [OR] 1.50, 95% confidence interval [CI] 1.22-1.85). Other independent predictors of a cPRA ≥ 90% were parity (OR 1.26, 95% CI 1.08-1.47), age (OR 0.98, 95% CI 0.97-1.00), history of renal disease (OR 1.88, 95% CI 1.02-3.48), and number of non-leukoreduced products transfused (OR 1.02, 95% CI 1.00-1.04). CONCLUSIONS: RBC alloimmunization was significantly associated with HLA alloimmunization with a cPRA ≥ 90%. RBC alloimmunization status combined with specific components of the clinical history may estimate the risk of high-level HLA alloimmunization.

Severe CD4+ T-cell lymphopenia is not observed in frequent plateletpheresis donors collected on the Fenwal Amicus.

BACKGROUND: In a recent study, we determined that 30% of frequent plateletpheresis donors collected using the Trima Accel Automated Blood Collection System (Terumo BCT) had a CD4+ T-cell count below 200 cells/µL. Whether CD4+ T-cell lymphopenia is associated with donation using other plateletpheresis instruments is unknown. STUDY DESIGN AND METHODS: We obtained blood samples from 30 current frequent Fenwal Amicus plateletpheresis donors. All participants had made 20 to 24 plateletpheresis donations in the most recent 365-day period, and all had previously donated over 50 times on the Fenwal Amicus instrument. Blood samples were analyzed to determine blood counts, including CD4+ and CD8+ counts. RESULTS: Of 30 study participants, none had a CD4+ count below 200 cells/µL. There was one participant with a CD4+ count between 200 and 300 cells/µL. This individual was over the age of 55 and had a history of more than 300 lifetime plateletpheresis sessions. One participant had a CD8+ count below the lower limit of normal (125 cells/µL) and a normal CD4+ count. CONCLUSION: We did not detect severe CD4+ lymphopenia in frequent platelet donors undergoing plateletpheresis with the Fenwal Amicus. Since the Fenwal Amicus does not incorporate a leukoreduction system chamber, this finding supports the hypothesis that such chambers-found in the Trima Accel instrument-contribute to CD4+ lymphopenia in frequent platelet donors.

Clinical features and outcomes in patients with thrombotic microangiopathy not associated with severe ADAMTS13 deficiency.

BACKGROUND: The a disintegrin and metalloprotease with thrombospondin type 1 motifs, member 13 (ADAMTS13) activity assay has become important in distinguishing autoimmune thrombotic thrombocytopenic purpura from other forms of thrombotic microangiopathy (TMA). Although the significance of severe deficiency in ADAMTS13 (activity levels 10% or less) has been well defined, little data are available on the clinical importance of mild to moderate deficiency (activity levels 11%-70%) among patients with TMA. STUDY DESIGN AND METHODS: We conducted a retrospective study using the Harvard TMA Research Collaborative Registry. Among 254 patients who met the inclusion criteria for TMA, 186 patients with ADAMTS13 activity levels greater than 10% were divided into moderate-deficiency (11%-40%), mild-deficiency (41%-70%), and no-deficiency (greater than 70%). RESULTS: Compared with mild or no deficiency, moderate ADAMTS13 deficiency correlated with older age; higher bilirubin and international normalized ratio; and increased frequency of sepsis, shock, or multiorgan failure. Platelet counts, lactate dehydrogenase levels, and the presence of renal or neurologic dysfunction did not vary across the three patient cohorts. While moderate ADAMTS13 deficiency was associated with increased 90-day mortality in univariate analysis, this association was no longer significant in multivariate analysis. Variables that independetly predicted 90-day mortality in this cohort of patients included Charlson comorbidity index, alanine aminotransferase level, platelet count, creatinine, and the presence of sepsis, shock, or multiorgan failure. CONCLUSION: Moderately deficient ADAMTS13 activity identifies a cohort of patients with TMA who are at increased risk for 90-day mortality. The ADAMTS13 activity level in this group is not an independent predictor of poor outcomes but instead appears to be a marker of disease acuity.

Treatment with or without plasma exchange for patients with acquired thrombotic microangiopathy not associated with severe ADAMTS13 deficiency: a propensity score-matched study.

BACKGROUND: Therapeutic plasma exchange (TPE) is a proven treatment for thrombotic thrombocytopenic purpura (TTP) characterized by severe ADAMTS13 deficiency, but the efficacy of TPE in suspected TTP with an ADAMTS13 activity level of more than 10% remains controversial. STUDY DESIGN AND METHODS: We conducted a propensity score (PS)-matched study of 186 adult patients included in the Harvard Thrombotic Microangiopathy (TMA) Research Collaborative registry who presented with TMA suggestive of TTP but an ADAMTS13 activity level of more than 10%. RESULTS: Before matching, patients treated with TPE (n = 71) differed from untreated patients (n = 115) by several clinical measures. PS matching was performed to address clinical disparities between the two groups and resulted in a well-balanced cohort of 59 TPE-treated patients paired with 59 untreated controls, all of whom had TMA. After matching, we observed no significant difference in the primary outcome of 90-day survival between the treated and untreated groups (hazard ratio, 0.88; 95% confidence interval [CI], 0.44-1.77; p = 0.72). In-hospital mortality (odds ratio [OR], 0.77; 95% CI, 0.34-1.75; p = 0.53) and the percentage of patients with platelet count recovery (OR, 1.58; 95% CI, 0.77-3.26; p = 0.21) also did not differ significantly between the two matched groups. CONCLUSION: Our data suggest that routine use of TPE in the diverse group of TMA patients without severe ADAMTS13 deficiency may not significantly improve outcomes.

Impact of severe ADAMTS13 deficiency on clinical presentation and outcomes in patients with thrombotic microangiopathies: the experience of the Harvard TMA Research Collaborative.

The Harvard TMA Research Collaborative is a multi-institutional registry-based effort to study thrombotic microangiopathies (TMA). Laboratory and clinical parameters were recorded for 254 cases of suspected autoimmune thrombotic thrombocytopenic purpura (TTP). Patients with severe ADAMTS13 deficiency (activity ≤10%, N = 68) were more likely to be young, female and without a history of cancer treatment or transplantation. While all patients with severe deficiency were diagnosed with autoimmune TTP, those without severe deficiency frequently had disseminated intravascular coagulation, drug-associated TMA and transplant-related TMA. Patients with severe ADAMTS13 deficiency had superior overall survival at 360 d compared to those without severe deficiency (93·0% vs. 47·5%, P < 0·0001). Almost all patients with severe deficiency received therapeutic plasma exchange (TPE), but the use of TPE in patients with ADAMTS13 activity >10% varied significantly across the institutions in our consortium (13·2-63·8%, P < 0·0001). Nevertheless, 90-d mortality was not different in patients with ADAMTS13 activity >10% between the three hospitals (P = 0·98). Our data show that patients with severe ADAMTS13 deficiency represent a clinically distinct cohort that responds well to TPE. In contrast, TMA without severe ADAMTS13 deficiency is associated with increased mortality that may not be influenced by TPE.

Difficulties in hematopoietic progenitor cell collection from a patient with TEMPI syndrome and severe iatrogenic iron deficiency.

BACKGROUND: Collection of hematopoietic progenitor cells by apheresis (HPC-A) requires separation of cells by density. Previous studies highlighted the challenges of HPC-A collection from patients with abnormal red blood cells (RBCs). TEMPI syndrome is a recently described condition defined by teleangiectasias, elevated erythropoietin and erythrocytosis, monoclonal gammopathy, perinephric fluid collections, and intrapulmonary shunting. Patients with TEMPI syndrome have responded to therapies used to treat plasma cell dyscrasias and may benefit from autologous HPC transplantation. We report HPC-A collection from a patient with TEMPI syndrome that was complicated by severe iron deficiency. STUDY DESIGN AND METHODS: The patient received granulocyte-colony-stimulating factor (G-CSF) and plerixafor for HPC mobilization and underwent 3 days of HPC-A collection. RESULTS: The patient presented for collection with a microcytic erythrocytosis. Over 3 days, approximately 50 L of whole blood was processed, and 2 × 10(8) CD34+ cells were collected (2.8 × 10(6) CD34+ cells/kg). The mean collection efficiency (CE), percentage of mononuclear cells, hematocrit (Hct), and RBC count were 18%, 90%, 14%, and 9 × 10(11) , respectively. Altering collection variables to avoid RBC contamination reduced CE. Ficoll preparations of the products after freeze-thaw showed RBC contamination and hemolysis. Postthaw viability exceeded 95%. The products were not RBC reduced or washed. There were no adverse reactions during or after infusion. CONCLUSIONS: HPC-A collection from a patient with TEMPI syndrome was complicated by microcytic erythrocytosis, leading to RBC contamination and hemolysis in the product. Adequate HPCs were collected and the patient tolerated infusion without RBC depletion or washing. Our report highlights difficulties of HPC-A collection from iron-deficient patients.

Reduced Albumin Dosing During Large-Volume Paracentesis Is Not Associated with Adverse Clinical Outcomes.

BACKGROUND: LVP is used to manage diuretic-resistant ascites in cirrhotic patients. Albumin administration prevents complications including acute kidney injury and paracentesis-induced circulatory dysfunction, but the optimal dose is unclear. AIM: We sought to assess adherence to guidelines enacted in July 2011 at our center for reducing the albumin dose administered at large-volume paracentesis (LVP) and evaluate the cost and rate of complications of LVPs before and after guideline enactment. METHODS: All LVPs performed on cirrhotic patients in our center's Department of Radiology between July 2009 and January 2014 were studied. Outcomes included adherence to guidelines, LVP complications, and administered albumin cost. Groups were compared using Student's t tests for continuous data and Chi-square or Fisher's exact tests for categorical data. A repeated measurements model accounted for patients with multiple LVPs. RESULTS: Of the 935 LVPs, 288 occurred before guideline implementation (group 1) and 647 occurred after (group 2). The mean dose of albumin administered was 13.7 g/L of ascites removed in group 1 versus 10.3 g/L in group 2 (p < 0.0001). Of the group 2 LVPs, 235 (36.3 %) adhered to guidelines. There were no significant differences in LVP complications. CONCLUSIONS: Guidelines were followed in one-third of LVPs. Despite this limited adherence, a reduction in albumin administration and associated cost savings was still observed. There was no increase in LVP-related complications after guideline implementation or in the adherent group, suggesting that albumin dose can be safely reduced. Future efforts should be directed at enhancing guideline adherence and potentially further reducing albumin dosing.

Anti-HLA alloantibodies in surgical patients refractory to platelet transfusion.

Alloimmune platelet refractoriness (alloPR) among actively bleeding surgical patients with thrombocytopenia represents a life-threatening problem. Here we present three cases in which surgical bleeding was complicated by life-threatening thrombocytopenia and alloPR. We demonstrate that the human leukocyte antigens (HLA) antibodies associated with alloPR are broadly reactive and in high concentration, are not removed by hemodilution, and are not absorbed by transfusion of multiple doses of platelet concentrates. HLA alloPR may be under-recognized among surgical patients. Research is needed to develop pre-operative screening methods that will identify patients in need of specialized platelet support using HLA compatible donor products.

Thrombopoietin levels in patients with disorders of platelet production: diagnostic potential and utility in predicting response to TPO receptor agonists.

Thrombopoietin (TPO) is the major regulator of megakaryopoiesis. Measurement of serum TPO levels may help distinguish between various causes of thrombocytopenia and predict treatment response to TPO receptor agonists. Serum TPO levels from 118 healthy volunteers and 88 patients with abnormal platelet counts were measured using a quantitative ELISA assay. The mean (range) TPO level in healthy volunteers was 39 (7-99) pg/mL. TPO values were correlated with the patient's diagnosis, platelet count, and response to TPO receptor agonists. 88 patients with history of consumptive thrombocytopenia (39) or hypoproliferative thrombocytopenia (49) were analyzed. Median (interquartile range) TPO level for consumptive thrombocytopenia patients was 63 (48-98) pg/mL with a corresponding median (interquartile range) platelet count of 73 (28-146) × 10(9) /L. In contrast, hypoproliferative thrombocytopenia patients had platelet counts [59 (30-117) × 10(9) /L] comparable with consumptive thrombocytopenia patients, but significantly higher serum TPO levels [706 (358-1546) pg/mL, P < 0.0001]. Analysis of 21 ITP patients treated with TPO receptor agonists demonstrated that a TPO level >95 pg/mL was associated with lack of clinical response (P < 0.002). TPO levels may have diagnostic utility in discriminating between patients with hypoproliferative and consumptive thrombocytopenia. Elevated TPO levels in ITP patients may predict a poor clinical response to treatment with TPO receptor agonists.

Computer vision quantitation of erythrocyte shape abnormalities provides diagnostic, prognostic, and mechanistic insight.

Examination of red blood cell (RBC) morphology in peripheral blood smears can help diagnose hematologic diseases, even in resource-limited settings, but this analysis remains subjective and semiquantitative with low throughput. Prior attempts to develop automated tools have been hampered by their poor reproducibility and limited clinical validation. Here, we present a novel, open-source machine-learning approach (denoted as RBC-diff) to quantify abnormal RBCs in peripheral smear images and generate an RBC morphology differential. RBC-diff cell counts showed high accuracy for single-cell classification (mean AUC, 0.93) and quantitation across smears (mean R2, 0.76 compared with experts, interexperts R2, 0.75). RBC-diff counts were concordant with the clinical morphology grading for 300 000+ images and recovered the expected pathophysiologic signals in diverse clinical cohorts. Criteria using RBC-diff counts distinguished thrombotic thrombocytopenic purpura and hemolytic uremic syndrome from other thrombotic microangiopathies, providing greater specificity than clinical morphology grading (72% vs 41%; P < .001) while maintaining high sensitivity (94% to 100%). Elevated RBC-diff schistocyte counts were associated with increased 6-month all-cause mortality in a cohort of 58 950 inpatients (9.5% mortality for schist. >1%, vs 4.7% for schist; <0.5%; P < .001) after controlling for comorbidities, demographics, clinical morphology grading, and blood count indices. RBC-diff also enabled the estimation of single-cell volume-morphology distributions, providing insight into the influence of morphology on routine blood count measures. Our codebase and expert-annotated images are included here to spur further advancement. These results illustrate that computer vision can enable rapid and accurate quantitation of RBC morphology, which may provide value in both clinical and research contexts.

Pathway-driven rare germline variants associated with transplant-associated thrombotic microangiopathy (TA-TMA).

The significance of rare germline mutations in transplant-associated thrombotic microangiopathy (TA-TMA) is not well studied. We performed a genetic association study in 100 adult TA-TMA patients vs. 98 post-transplant controls after matching by race, sex, and year. We focused on 5 pathways in complement, von Willebrand factor (VWF) function and related proteins, VWF clearance, ADAMTS13 function and related proteins, and endothelial activation (3641variants in 52 genes). In the primary analysis focused on 189 functional rare variants, no differential variant enrichment was observed in any of the pathways; specifically, 29 % TA-TMA and 33 % controls had at least 1 rare complement mutation. In the secondary analysis focused on 37 rare variants predicted to be pathogenic or likely pathogenic by ClinVar, Complement Database, or REVEL in-silico prediction tool, rare variants in the VWF clearance pathway were found to be significantly associated with TA-TMA (p = 0.008). On the gene level, LRP1 was the only one with significantly increased variants in TA-TMA in both analyses (p = 0.025 and 0.015). In conclusion, we did not find a significant association between rare variants in the complement pathway and TA-TMA; however, we discovered a new signal in the VWF clearance pathway driven by the gene LRP1 among likely pathogenic variants.