Bethesda Assay for Detecting Inhibitory Anti-ADAMTS13 Antibodies in Immune-Mediated Thrombotic Thrombocytopenic Purpura

AbstractA diagnosis of thrombotic thrombocytopenic purpura (TTP) is confirmed by a severe deficiency (<10%) of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) activity. Autoantibodies to ADAMTS13 can be detected with a simplified enzyme-linked immunosorbent assay (ELISA). An alternative methodology is a Bethesda assay, which has never been formally assessed in TTP. This study aimed to investigate the inhibitory anti-ADAMTS13 antibody assay and determine if the Bethesda assay is advantageous compared with the ELISA, measuring total immunoglobulin G (IgG) antibodies to ADAMTS 13. The Bethesda method determines the neutralizing activity of anti-ADAMTS13 antibodies in pooled normal plasma. We selected six immune-mediated TTP (iTTP) patients with ADAMTS13 activity levels <10% and strong ADAMTS13 inhibitors by 50:50 mixing studies and analyzed anti-ADAMTS13 antibodies using the Bethesda and ELISA assays. ADAMTS13 activity was stable at room temperature, while a time-dependent decrease in activity was detected in assay conditions of 37°C. Adding 5 mM Ca2+ to citrated plasma prevented loss of ADAMTS13 activity with time. There was time dependence to the antibody-mediated inactivation, after 2-hour incubation. Two of the iTTP patients had no detectable ADAMTS13 antibodies by the Bethesda assay, but had high titer of anti-ADAMTS13 antibodies and low ADAMTS13 antigen levels. The Bethesda assay can only detect anti-ADAMTS13 antibodies that functionally inhibit ADAMTS13. The anti-ADAMTS13 IgG ELISA instead allows the rapid identification of total IgG autoantibodies, detecting both inhibitory and noninhibitory antibodies.

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Exome Sequencing Identifies Glycosylation Defects as a Probable Cause of Immune-Mediated Thrombotic Thrombocytopenic Purpura

American Journal of Clinical Pathology ◽

10.1093/ajcp/aqz112.037 ◽

2019 ◽

Vol 152 (Supplement_1) ◽

pp. S19-S20

Author(s):

Malay Kumar Basu ◽

Elizabeth Staley ◽

Konstantine Halkidis ◽

Jingrui (Jean) Sui ◽

Nicole K Kocher ◽

...

Keyword(s):

Exome Sequencing ◽

Thrombotic Thrombocytopenic Purpura ◽

Potential Contribution ◽

Healthy Controls ◽

Adamts13 Activity ◽

Autoantibody Production ◽

Thrombocytopenic Purpura ◽

Long Term Outcome ◽

Immune Mediated ◽

Severe Deficiency

Abstract Background Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a potentially fatal syndrome, resulting from autoantibodies against ADAMTS13. However, the mechanism underlying autoantibody formation is not known. Neither is known about the other genetic abnormality in the setting of severe deficiency of plasma ADAMTS13 activity. Methods Whole-exome sequencing (WES) was performed in 40 patients with iTTP who had plasma ADAMTS13 activity <10% and a positive inhibitor or elevated anti-ADAMTS13 IgG. Fifteen age- and ethnicity-matched subjects who never had iTTP were recruited as healthy controls. Results WES identified mutations in the genes involved in glycosylation, including O-linked glycosylation to be the major pathway affected in patients with iTTP. Mass spectrometry confirmed the changes in plasma levels of various glycoproteins in patients with acute iTTP when compared with those in the healthy controls. The altered glycosylation in glycoproteins may be responsible for the development of autoantibodies, susceptibility of von Willebrand factor to proteolysis by ADAMTS13, and the clearance of platelets in iTTP patients. Moreover, candidate gene analysis revealed that various genes involving in hemostasis, complement activation, platelet number and function, and inflammation were all affected in patients with iTTP, which may contribute to the onset, progress, severity, and long-term outcome of iTTP. Conclusions Our findings provide novel insight into a pathogenic mechanism underlying autoantibody production and the potential contribution of other genetic abnormalities in pathogenesis of iTTP in the individuals with severe deficiency of plasma ADAMTS13 activity. Future Direction Further studies are warranted to determine the specific glycosylation patterns of various plasma and cellular proteins in patients with iTTP and to determine the synergistic role of various gene mutations and severe ADAMTS13 deficiency in the pathogenesis of iTTP.

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Anti-ADAMTS13 Antibodies and a Novel Heterozygous p.R1177Q Mutation in a Case of Pregnancy-Onset Immune-Mediated Thrombotic Thrombocytopenic Purpura

TH Open ◽

10.1055/s-0037-1615252 ◽

2018 ◽

Vol 02 (01) ◽

pp. e8-e15 ◽

Cited By ~ 2

Author(s):

Elien Roose ◽

Claudia Tersteeg ◽

Ruth Demeersseman ◽

An-Sofie Schelpe ◽

Louis Deforche ◽

...

Keyword(s):

Genetic Analysis ◽

Thrombotic Thrombocytopenic Purpura ◽

Acute Phase ◽

Activity Levels ◽

The Novel ◽

Adamts13 Activity ◽

Thrombocytopenic Purpura ◽

Linker Region ◽

The Third ◽

Immune Mediated

In this study, we investigated a case of pregnancy-onset thrombotic thrombocytopenic purpura (TTP). The patient had severely decreased ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 motif, member 13) activity levels during acute phase and the presence of inhibitory anti-ADAMTS13 autoantibodies was demonstrated, which led to the diagnosis of immune-mediated TTP. However, ADAMTS13 activity was only mildly restored during remission, although inhibitory anti-ADAMTS13 antibodies were no longer detected. We hypothesized that genetic abnormalities could account for this discrepancy between ADAMTS13 activity and antigen. Genetic analysis revealed the presence of two heterozygous substitutions on the same allele: a single nucleotide polymorphism (SNP) c.2699C > T (p.A900V), located in the beginning of the T5 domain, and a mutation c.3530G > A (p.R1177Q) located in the third linker region of ADAMTS13. In vitro testing of those substitutions by expression of recombinant proteins revealed a normal secretion but a reduced ADAMTS13 activity by the novel p.R1177Q mutation, which could partially explain the subnormal activity levels found during remission. Although changes in the linker region might induce conformational changes in ADAMTS13, the p.R1177Q mutation in the third linker region of ADAMTS13 did not expose a cryptic epitope in the metalloprotease domain. In conclusion, we report on an immune-mediated pregnancy-onset TTP patient who had inhibitory anti-ADAMTS13 autoantibodies during acute phase, but not during remission. Genetic analysis confirmed the diagnosis of immune-mediated TTP and revealed the novel p.R1177Q mutation which mildly impaired ADAMTS13 activity.

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Correlation Of ADAMTS13 Activity With Baseline Characteristics and Management Patterns In Patients With Suspected Thrombotic Thrombocytopenic Purpura In The State Of Rhode Island

Blood ◽

10.1182/blood.v122.21.3556.3556 ◽

2013 ◽

Vol 122 (21) ◽

pp. 3556-3556

Author(s):

Nathan T. Connell ◽

Joseph D. Sweeney

Keyword(s):

Plasma Exchange ◽

Thrombotic Thrombocytopenic Purpura ◽

Rhode Island ◽

Turnaround Time ◽

Activity Level ◽

Activity Levels ◽

Adamts13 Activity ◽

Thrombocytopenic Purpura ◽

Baseline Characteristics ◽

Pre Treatment

Abstract Introduction While the activity level of ADAMTS13 can be helpful in diagnosing patients with thrombotic thrombocytopenic purpura (TTP), the current long turnaround time of this test for most institutions limits its role in early clinical decision-making about the initiation of plasma exchange. Levels of ADAMTS13<10% are pathognomonic of TTP and levels in excess of 10% indicate an alternate cause of thrombotic microangiopathy. The aim of the study was to look at recent practice in the State of Rhode Island regarding the criteria for initiation of plasma exchange with a subsequent categorization of those patients based on ADAMTS13 activity levels. Methods Patients with a diagnosis of TTP were identified from hospital records of the major hospitals in Rhode Island which perform therapeutic apheresis in calendar years 2011 and 2012. From a chart review and blood bank records, baseline clinical parameters were collected, the number of therapeutic plasma exchanges (TPE) performed and the volume of plasma utilized. Pre-treatment ADAMTS13 activity was recorded if available in addition to the number of days from the initiation of TPE to test result availability. An analysis was performed to examine if patients who had a pre-treatment ADAMTS13 activity level ≤10% differed in baseline characteristics or response to TPE from those with activity levels >10%. Based on the normality of the distribution of the data, independent t-tests or Wilcoxon rank-sum tests were performed using SAS version 9.3. Results During this two year period, 24 patients received plasma exchange in Rhode Island for a presumptive diagnosis of TTP. The mean age was 47 years (range 20-89 years) and 38% were male. ADAMTS13 activity was available for 20 patients and 7 (30% of those exchanged) had documented pre-treatment activity levels ≤10% consistent with TTP. The median turnaround time for the ADAMTS13 assay was 10 days (range 2-52). Mean baseline parameters at the time of presentation are shown in the table. As expected, creatinine levels were lower in those patients with true TTP (p=0.0410). ADAMTS13 activity level was predictive of the number of days to a platelet count ≥150 x 109/L (Pearson correlation 0.56; p-value 0.0458). Overall, 4238 units of plasma were utilized for exchange. Of these 4238 units, 1886 were transfused to patients who were subsequently shown to have an ADAMTS13 activity >10%, and 813 of the 1886 units (20% of all plasma exchanged) were transfused after the results of enzyme activity were available in this population. Conclusions Based on an ADAMTS13 >10%, a significant volume of plasma was unnecessarily transfused. Reducing the turnaround time for the ADAMTS13 assay in tertiary care centers could help clinicians better determine which patients will benefit from plasma exchange, avoiding the morbidity and expense associated with large volume plasma exchange. Disclosures: No relevant conflicts of interest to declare.

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FRETS-VWF73 rather than CBA assay reflects ADAMTS13 proteolytic activity in acquired thrombotic thrombocytopenic purpura patients

Thrombosis and Haemostasis ◽

10.1160/th13-08-0688 ◽

2014 ◽

Vol 112 (08) ◽

pp. 297-303 ◽

Cited By ~ 13

Author(s):

Ilaria Mancini ◽

Carla Valsecchi ◽

Luca Lotta ◽

Louis Deforche ◽

Silvia Pontiggia ◽

...

Keyword(s):

Thrombotic Thrombocytopenic Purpura ◽

Proteolytic Activity ◽

Binding Activity ◽

Adamts13 Activity ◽

Flow Conditions ◽

Thrombocytopenic Purpura ◽

Severe Deficiency ◽

Adamts13 Deficiency ◽

Von Willebrand ◽

Willebrand Factor

SummaryCollagen-binding activity (CBA) and FRETS-VWF73 assays are widely adopted methods for the measurement of the plasmatic activity of ADAMTS13, the von Willebrand factor (VWF) cleaving-protease. Accurately assessing the severe deficiency of ADAMTS13 is important in the management of thrombotic thrombocytopenic purpura (TTP). However, non-concordant results between the two assays have been reported in a small but relevant percentage of TTP cases. We investigated whether CBA or FRETS-VWF73 assay reflects ADAMTS13 proteolytic activity in acquired TTP patients with non-concordant measurements. Twenty plasma samples with non-concordant ADAMTS13 activity results, <10% using FRETS-VWF73 and ≥20% using CBA, and 11 samples with concordant results, <10% using either FRETS-VWF73 and CBA assays, were analysed. FRETS-VWF73 was performed in the presence of 1.5 M urea. ADAMTS13 activities were also measured under flow conditions and the VWF multimer pattern was defined in order to verify the presence of ultra-large VWF due to ADAMTS13 deficiency. In FRETS-VWF73 assay with 1.5 M urea, ADAMTS13 activity significantly increased in roughly 50% of the samples with non-concordant results, whereas it remained undetectable in all samples with concordant measurements. Under flow conditions, all tested samples showed reduced ADAMTS13 activity. Finally, samples with non-concordant results showed a ratio of high molecular weight VWF multimers higher than normal. Our results support the use of FRETS-VWF73 over CBA assay for the assessment of ADAMTS13 severe deficiency and indicate urea as one cause of the observed differences.

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Open ADAMTS13, induced by antibodies, is a biomarker for subclinical immune-mediated thrombotic thrombocytopenic purpura

Blood ◽

10.1182/blood.2019004221 ◽

2020 ◽

Cited By ~ 4

Author(s):

Elien Roose ◽

An-Sofie Schelpe ◽

Edwige Tellier ◽

György Sinkovits ◽

Bérangère S Joly ◽

...

Keyword(s):

Thrombotic Thrombocytopenic Purpura ◽

Adamts13 Activity ◽

Thrombocytopenic Purpura ◽

Follow Up Study ◽

Open Conformation ◽

Immune Mediated ◽

Long Term Follow Up ◽

Donor Plasma

Recently, we showed that during the acute phase of immune-mediated thrombotic thrombocytopenic purpura (iTTP), ADAMTS13 circulates in an open conformation. Although the cause of this conformational change in acute iTTP remains elusive, ADAMTS13 is mainly closed in iTTP patients (i) in remission with an ADAMTS13 activity >50% and undetectable anti-ADAMTS13 autoantibodies, and (ii) after rituximab treatment, suggesting a role for anti-ADAMTS13 autoantibodies. Therefore, IgGs from 18 acute iTTP patients were purified and added to closed ADAMTS13 in healthy donor plasma. This resulted in open ADAMTS13 in 14/18 (78%) samples, proving that indeed anti-ADAMTS13 autoantibodies can induce an open ADAMTS13 conformation. To further elucidate the conformation of ADAMTS13 in iTTP patients, we studied a novel iTTP patient cohort (n=197) that also included plasma samples of iTTP patients in remission where ADAMTS13 activity was <50%. The open ADAMTS13 conformation was not only found during acute iTTP but also in patients in remission with an ADAMTS13 activity <50% and in half of the patients with an ADAMTS13 activity >50%, although free anti-ADAMTS13 autoantibodies were not always detected. Thus open ADAMTS13 is not only a hallmark of acute iTTP, but also a novel biomarker to detect subclinical iTTP in patients in remission. Finally, a long term follow-up study in one iTTP patient showed that the open conformation precedes a severe drop in ADAMTS13 activity. In conclusion, we have shown that anti-ADAMTS13 autoantibodies from iTTP patients induce an open ADAMTS13 conformation. Most importantly, an open ADAMTS13 conformation is a biomarker for subclinical iTTP and could become an important tool in TTP management.

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Relative incidence of thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome in clinically suspected cases of thrombotic microangiopathy

Clinical Kidney Journal ◽

10.1093/ckj/sfz066 ◽

2019 ◽

Vol 13 (2) ◽

pp. 208-216 ◽

Cited By ~ 1

Author(s):

Ulf Schönermarck ◽

Wolfgang Ries ◽

Bernd Schröppel ◽

Lars Pape ◽

Malgorzata Dunaj-Kazmierowska ◽

...

Keyword(s):

Serum Creatinine ◽

Thrombotic Thrombocytopenic Purpura ◽

Haemolytic Uraemic Syndrome ◽

Primary Objective ◽

Adamts13 Activity ◽

Cross Sectional ◽

Thrombocytopenic Purpura ◽

Relative Incidence ◽

Severe Deficiency ◽

Post Hoc

Abstract Background Data are lacking on the relative incidence of thrombotic thrombocytopenic purpura (TTP), haemolytic uraemic syndrome (HUS) caused by Shiga toxin–producing Escherichia coli (STEC) and atypical HUS (aHUS) in patients presenting with thrombotic microangiopathies (TMAs). Methods This was a prospective, cross-sectional, multicentre and non-interventional epidemiological study. Patients fulfilling criteria for TMAs (platelet consumption, microangiopathic haemolytic anaemia and organ dysfunction) were included in the study. The primary objective was to assess the relative incidence of TTP, STEC-HUS, aHUS and ‘other’ physician-defined diagnoses. The secondary objective was to develop an algorithm to predict a severe deficiency in ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) activity (≤10%) using routine laboratory parameters. A post hoc classification using the recent Kidney Disease: Improving Global Outcomes diagnostic criteria was then undertaken to further classify patient groups. Results aHUS was diagnosed with a relative incidence of 61%, whereas TTP, STEC-HUS and ‘other’ were diagnosed in 13, 6 and 20% of patients, respectively. In the post hoc analysis, 27% of patients with a TMA were classified as ‘primary aHUS’ and 53% as ‘secondary aHUS’. Multivariate analysis revealed that severe deficiency in ADAMTS13 activity (≤10%) was unlikely to underlie TMA if platelet and serum creatinine were above threshold values of 30 × 109/L and 1.8 mg/dL, respectively (negative predictive value of 92.3 and 98.1, respectively, if one or both values were above the threshold). Conclusions In this study, aHUS was the most common single diagnosis among patients presenting with a TMA. In the absence of an ADAMTS13 activity result, platelet count and serum creatinine may aid in the differential diagnosis.

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Effect of plasma exchange on plasma ADAMTS13 metalloprotease activity, inhibitor level, and clinical outcome in patients with idiopathic and nonidiopathic thrombotic thrombocytopenic purpura

Blood ◽

10.1182/blood-2003-11-4035 ◽

2004 ◽

Vol 103 (11) ◽

pp. 4043-4049 ◽

Cited By ~ 318

Author(s):

X. Long Zheng ◽

Richard M. Kaufman ◽

Lawrence T. Goodnough ◽

J. Evan Sadler

Keyword(s):

Plasma Exchange ◽

Thrombotic Thrombocytopenic Purpura ◽

High Titer ◽

Patient Treatment ◽

Adamts13 Activity ◽

Thrombocytopenic Purpura ◽

Hematopoietic Stem ◽

Complete Clinical Remission ◽

Inhibitor Level

Abstract Therapeutic plasma exchange is an effective empiric treatment for thrombotic thrombocytopenic purpura (TTP), but how therapy affects the level of adisintegrin and metalloprotease with thrombospondin type 1 motif 13 (ADAMTS13) or inhibitor has not been reported in many patients. We prospectively analyzed ADAMTS13 activity and inhibitor levels in 37 adults with TTP. ADAMTS13 level at presentation was lower than 5% in 16 of 20 patients with idiopathic TTP and in none of 17 patients with TTP associated with hematopoietic stem cell transplantation, cancer, drugs, or pregnancy (P < .00001). Seven of the 16 patients with ADAMTS13 activity lower than 5% (≈ 44%) had inhibitors. For 8 patients followed serially with ADAMTS13 activity lower than 5% but no inhibitor at presentation, plasma exchange led to complete clinical remission and a rise in ADAMTS13 level. In contrast, 4 patients with low ADAMTS13 activity but high-titer inhibitor (> 5 units/mL) had neither a rise in ADAMTS13 activity nor a reduction in the inhibitor titer: 3 had recurrent disease and 1 died. Among 17 patients with AD-AMTS13 activity at presentation higher than 25%, 10 died. Mortality rate for idiopathic TTP was 15%, whereas mortality for nonidiopathic TTP was 59% (P < .02). We conclude that assays of ADAMTS13 activity and inhibitors in addition to the clinical categories (idiopathic TTP and nonidiopathic TTP) are predictive of outcome and may be useful to tailor patient treatment.

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Diagnostic relevance of ADAMTS13 activity: Evaluation of 28 patients with thrombotic thrombocytopenic purpura - hemolytic uremic syndrome clinical diagnosis

Srpski arhiv za celokupno lekarstvo ◽

10.2298/sarh1308466v ◽

2013 ◽

Vol 141 (7-8) ◽

pp. 466-474

Author(s):

Dragica Vucelic ◽

Danijela Mikovic ◽

Zoran Rajic ◽

Nebojsa Savic ◽

Zivko Budisin ◽

...

Keyword(s):

Hemolytic Uremic Syndrome ◽

Thrombotic Thrombocytopenic Purpura ◽

Binding Activity ◽

Adamts13 Activity ◽

Activity Assay ◽

Thrombocytopenic Purpura ◽

Uremic Syndrome ◽

Adamts13 Deficiency ◽

A Disintegrin And Metalloproteinase ◽

Thrombospondin Motif

Introduction. The significance of ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin motif-13) activity for diagnosis and therapy of thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) is still a controversial issue. Objective. The aim of this report was to analyze the value of ADAMTS13 measurements in the diagnosis of TTP and HUS. Methods. At presentation, we analyzed patients with idiopathic TTP (n=18), secondary TTP (n=4), diarrhea positive HUS (n=3) and diarrhea negative HUS (n=3) treated in Belgrade, Serbia from 2004 to 2010. ADAMTS13 activity from acute phase samples was measured using the residual collagen binding activity assay at the Haemophilia and Thrombosis Centre, Milan, Italy. Results. There was a significant correlation between reduced ADAMTS13 activity and idiopathic TTP diagnosis (p=0.000) as well as between lower ADAMTS13 activities and higher reticulocytes (p=0.017) and lactate dehydrogenase levels (p=0.027). Significant correlation was also found between higher protease activity and diagnosis of HUS (p=0.000). There was a statistically significant correlation between higher ADAMTS13 activities and higher platelets count (p=0.002), blood urea nitrogen (p=0.000), and creatinine level (p=0.000). Conclusion. Severe ADAMTS13 deficiency points at the diagnosis of idiopathic TTP and it is present in the secondary TTP but not in HUS.

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Residual plasmatic activity of ADAMTS13 is correlated with phenotype severity in congenital thrombotic thrombocytopenic purpura

Blood ◽

10.1182/blood-2012-01-403113 ◽

2012 ◽

Vol 120 (2) ◽

pp. 440-448 ◽

Cited By ~ 74

Author(s):

Luca A. Lotta ◽

Haifeng M. Wu ◽

Ian J. Mackie ◽

Marina Noris ◽

Agnes Veyradier ◽

...

Keyword(s):

Thrombotic Thrombocytopenic Purpura ◽

Limit Of Detection ◽

Clinical Phenotype ◽

Characteristic Curve ◽

Activity Levels ◽

Dependent Manner ◽

Adamts13 Activity ◽

Thrombocytopenic Purpura ◽

Plasma Infusion ◽

Congenital Thrombotic Thrombocytopenic Purpura

Abstract The quantification of residual plasmatic ADAMTS13 activity in congenital thrombotic thrombocytopenic purpura (TTP) patients is constrained by limitations in sensitivity and reproducibility of commonly used assays at low levels of ADAMTS13 activity, blunting efforts to establish genotype-phenotype correlations. In the present study, the residual plasmatic activity of ADAMTS13 was measured centrally by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (limit of detection = 0.5%) in 29 congenital TTP patients. The results were used to study correlations among ADAMTS13 genotype, residual plasmatic activity, and clinical phenotype severity. An ADAMTS13 activity above 0.5% was measured in 26 (90%) patients and lower levels of activity were associated with earlier age at first TTP episode requiring plasma infusion, more frequent recurrences, and prescription of fresh-frozen plasma prophylaxis. Receiver operating characteristic curve analysis showed that activity levels of less than 2.74% and 1.61% were discriminative of age at first TTP episode requiring plasma infusion < 18 years, annual rate of TTP episodes > 1, and use of prophylaxis. Mutations affecting the highly conserved N-terminal domains of the protein were associated with lower residual ADAMTS13 activity and a more severe phenotype in an allelic-dose dependent manner. The results of the present study show that residual ADAMTS13 activity is associated with the severity of clinical phenotype in congenital TTP and provide insights into genotype-phenotype correlations.

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Clinical and Outcomes Findings for Thrombotic Thrombocytopenic Purpura among 467 Persons with Severely Versus Not Severely Deficient ADAMTS-13 Levels.

Blood ◽

10.1182/blood.v110.11.2088.2088 ◽

2007 ◽

Vol 110 (11) ◽

pp. 2088-2088 ◽

Cited By ~ 3

Author(s):

Charles L. Bennett ◽

Thanh Ha Luu ◽

Anaadriana Zakarija ◽

Hau C. Kwaan ◽

Nicholas Bandarenko ◽

...

Keyword(s):

Thrombotic Thrombocytopenic Purpura ◽

Neutralizing Antibodies ◽

Clinical Laboratory ◽

Survival Rates ◽

Outcome Data ◽

Severe Thrombocytopenia ◽

Activity Levels ◽

Adamts13 Activity ◽

Thrombocytopenic Purpura ◽

Adamts13 Deficiency

Abstract Background: Thrombotic thrombocytopenic purpura (TTP) is a rare disorder that presents with microangiopathic hemolytic anemia and thrombocytopenia, fevers, renal insufficiency and neurologic features. We reviewed clinical, laboratory, and outcome data for TTP cases with severely deficient versus non-severely deficient ADAMTS13 activity levels. Methods: Mean and median data were from the Surveillance, Epidemiology and Risk Factors for TTP (SERF-TTP) study group for idiopathic TTP cases, the Canadian Apheresis Group (CAG), and five published series (Zheng 2004, Raife 2004, Vesely 2003 (Oklahoma TTP-HUS Registry), Matsumoto 2004 (Japan Referral Center), Bennett 2007). Results: Compared to TTP cases with near-normal ADAMTS13 activity levels (n= 282), TTP cases with severe ADAMTS13-deficiency (n=185) were more likely to have severe thrombocytopenia, normal renal function and neutralizing ADAMTS13 antibodies. Severe ADAMTS13 deficient TTP cases have better overall survival after therapeutic plasma exchange (TPE) but are more likely to relapse. TTP patients with severe ADAMTS13 deficiency were primarily categorized as idiopathic or ticlopidine-associated, while TTP patients with non-severely deficient ADAMTS13 activity levels were frequently categorized as idiopathic, secondary to drugs (clopidogrel, quinine), stem cell transplantation, or cancer. Conclusions: Severe ADAMTS13 deficiency is most commonly idiopathic, has better survival following TPE, and a 35–40% spontaneous relapse rate. By contrast, non-ADAMTS13 deficient TTP cases are usually associated with an underlying disorder or external insults. Amongst this cohort, four series have 47–62% survival rates and three series, which contain mostly idiopathic cases, have 83–90% survival rates following TPE. From this, we propose that TTP may occur by three possible mechanism; ADAMTS13-deficient (antibody-mediated), an immunologic mediated pathway independent of ADAMTS13 (i.e. quinine) that is responsive to TPE, and endothelial injury related TTP that is unresponsive to TPE. Platelet count mean (x10^9/L) Creatinine mean (mg/dl) ADAMTS13 neutralizing antibodies (%) Survival % Relapse % * <15% ADAMTS13 activity cutoff Severe ADAMTS13 Deficiency (<10–15%) SERF-TTP (n=30) 19 1.3 83 97 41 Zheng (n=16) 19 1.6 44 81 38 Bennett (n=26) 15 85 Oklahoma (n=18) 12 1.8 94 81 38 Raife (n=50) * 13 1.2 92 35 Japan (n=34) 35 91 Canada (n=11) 16 2.4 82 Not Severely Deficient ADAMTS13 Activity (> 15%) SERF-TTP (n=22) 57 3.9 35 90 0 Raife (n=57) * 44 2.7 83 9 Canada (n=17) 57 4.1 88 Zheng (n=13) 40 3.0 0 54 Bennett (n=13) 62 Japan (n=66) 9 62 Oklahoma (n=94 ) 23 47 3

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