Warad, Deepti

Abstract Background Lemierre's syndrome, sometimes referred to as postanginal septicemia or human necrobacillosis, is a multisystemic infection beginning in the oropharynx and leading to thrombosis of the internal jugular vein (IJV) with septic emboli and potential thrombotic extension to the central nervous system. This disorder occurs in the setting of oropharynx infection, leading to peritonsillar abscess. Within the abscess, anaerobic organisms penetrate the neighboring IJV resulting in an infected thrombus. Often polymicrobial, the infection is associated with the gram-negative bacillus Fusobacterium necrophorum, and if left untreated, may lead to fatal sepsis. With the advancement of antimicrobial therapies and earlier diagnosis of the disease, patient outcomes have improved. There is no clear consensus regarding the role of anticoagulation in this disorder. Some reports are in favor of anticoagulation therapy in conjunction with systemic antibiotic therapy while others support the use of antibiotic therapy alone. The purpose of this study is to better define the role of anticoagulation in this disorder and if thromboses outcomes are improved with anticoagulation therapy. Methods Pediatric and adult patients diagnosed with Lemierre's syndrome at the Mayo Clinic (Rochester, MN) between the years 1964 and 2014 were identified. Study inclusion criteria required radiologic confirmation of jugular vein thrombosis (JVT) in the setting of oropharynx infection, clinically diagnosed blood stream or local bacterial infection and intraoperative or radiological confirmation of head and neck loculated infection, and at least 3 months follow up. Patient demographics, clinical, microbiological and radiographic features, management and thromboses outcomes were reviewed. Thrombosis outcome was defined based on radiological findings defined as: CR (complete response-resolution of thrombus), PR (partial response-improvement with decrease in size of thrombus) and NR (no response). Progression/recurrence of thrombosis and bleeding complications data were also reviewed. Results Twenty-four patients were identified with the diagnosis of Lemierre's syndrome. Six patients were excluded due to lack of at least 3 months of follow up. Of the remaining 18 (8 females; 10 males) patients included in this analyses, 7 patients received anticoagulation therapy. Six patients were of the pediatric age group (<18 years). Median age of patients who received anticoagulation was 18.6 years [age range: 14-46.4 years]. Median age for the non-anticoagulated group was 19.2 years [age range: 16-71.8 years]. Microbiologically documented infective organisms were: Fusobacterium necrophorum (n=10), Fusobacterium necrophorum and Arcanobacterium heamolyticum (n=1), Staphylococcus aureus (n=2), Mycoplasma pneumoniae (n=1), Streptococcus pyogenes (n=1), others (n=3). Laterality of thrombosis presentation at diagnosis: right IJV (n=7), left IJV (n=6), bilateral IJV (n=2), left external jugular vein (n=3). Other site involvement/extension included pulmonary (n=2), cavernous sinus thrombosis (n=1), and sigmoid sinus thrombosis (n=1). All patients received broad-spectrum antibiotics. Seven patients received ≥4 weeks anticoagulation (median: 20.6 weeks; range 4-32.9 weeks]. Choice of anticoagulants and duration of anticoagulation practices were at the discretion of the treating physicians. Anticoagulation therapy consisted of unfractionated heparin (UFH) (n=1), UFH with transition to Coumadin (n=1), low molecular weight heparin (LMH) with transition to Coumadin (n=4), LMH (n=1). All patients had an improvement in their thrombus by 3 months (non-anticoagulated patient group: CR=9 and PR=2; anticoagulated patient group: CR=2 and PR=5). None of the patients developed recurrent thrombosis or progression during the follow up period regardless of their anticoagulation status. None of the patients who were anticoagulated developed bleeding complications. Conclusions This retrospective study suggests that anticoagulation in Lemierre's syndrome does not affect thrombosis outcomes. All patients achieved partial or complete thrombus resolution and no progression/recurrence of thrombus was noted in any patient regardless of whether anticoagulation status. Aggressive and prompt antimicrobial therapy remains the standard of care for this life-threatening disorder. Disclosures No relevant conflicts of interest to declare.

Abstract Introduction: The prevalence of venous thrombosis and pulmonary embolism (VTE) increases with age. Definitive VTE diagnosis or exclusion relies on imaging modalities, which are found to be negative in a high proportion of tested patients. Algorithms based on pretest clinical probability (low and intermediate) in conjunction with negative d-dimer test results have reliably excluded VTE sparing the need for additional imaging studies. Currently, the cutoff for a negative d-dimer is based on reference ranges regardless of age of the donor population. Since baseline d-dimer increases with aging, an age-adjusted d-dimer (AADD) cutoff for patients older than 50 years (age*10 ng/mL FEU) has been shown to improve specificity of diagnosis while still maintaining a high sensitivity (>97%) of detecting VTE/PE (Righini, et al. JAMA, 2014). Due to FDA restrictions, clinical laboratories cannot implement and report such AADD cutoffs. Major hurdles include: AADD cutoffs are assay-dependent, and there is a lack of feasible strategy for laboratories to verify the AADD cutoffs. We hypothesize that an adequate study of age-distribution of baseline d-dimer levels of healthy donors can assist the verification of AADD cutoffs and ultimately ensure patient safety in the VTE patient population. Objective: Establish an age dependent reference range for patients 50 years or older with the HemosIL HS 500 D-dimer reagent on the ACL TOP 700 (Instrumentation Laboratory, Bedford MA, USA); and compare this range with the manufacturer provided and literature recommended AADD cutoffs. Methods: D-dimer assay was performed on plasma samples from normal adult donors per the manufacturers' instructions. D-Dimer age, gender distribution and association were analyzed using non-parametric Wilcoxon rank sum, Kolmogorov-Smirnov tests, and quantile regression methods to estimate the 95th percentile to establish a reference range. Results: We studied 241 healthy donors, ranging from 21-91 years of age. Statistically significant differences between males and females (100 [42%] male) were detected (p-value <0.001; p-value =0.0009). Using CLSI guidelines, these statistical differences (median d-dimer for men = 200, while median d-dimer for women = 300) are not considered clinically significant, since only 6% of women would be outside an overall reference range (CLSI guideline states to partition if over 8% for either group would be outside the overall reference range). Using the quantile regression method, a significant association between d-dimer and age was found at the median (P<0.0001). We then established a reference range (95th percentile) for donors younger than age 50 at 635 ng/mL FEU for both men and women and AADD reference range for patients 50 and older (635 + (age - 50)*10 ng/mL) (Figure 1). This reference range was verified with our sample set, with only 6.2% of donors higher than the established reference limit. If we used the non-AADD cutoff provided by the manufacturer for donors younger than 50 (500 ng/mL FEU) and the literature recommended AADD cutoffs for older donors (age*10 ng/mL FEU), 13.3% of our normal donors were above the limits, resulting in not validating this literature reference range per CLSI guidelines in EP28-A3c. These data imply that if both manufacturer and literature recommended AADD cutoffs were adopted, HemosIL HS 500 D-dimer assay should have sufficient sensitivity and negative predictive value, although with slightly lower specificity than those reported by Righini, et al. for detecting VTE/PE. Conclusion: Our study verifies the association between d-dimer level and age and for the first time, to our knowledge, determined AADD normal range for the HemosIL HS 500 D-dimer assay. The manufacturer and literature recommended AADD cutoffs should provide sufficient sensitivity and negative predictive value for VTE/PE exclusion. Figure 1 Age distribution of D-Dimer values (n=241). Figure 1. Age distribution of D-Dimer values (n=241). Disclosures No relevant conflicts of interest to declare.

Abstract Hemorrhagic complications remain a challenge with surgical procedures in patients with bleeding disorders. Tonsillectomy and adenoidectomy are some of the most common surgical procedures performed in pediatric patients. Adequate hemostasis in patients with bleeding disorders is centered on comprehensive hemostatic support and dexterous surgical technique. To assess our institutional experience with children and young adults with bleeding disorders that underwent tonsillectomy and/or adenoidectomy we performed a retrospective chart review of all such patients (age< 25 years) over duration of 20 years from July 1992 to July 2012. Nineteen patients were identified. The mean age was 10.2 years (Range 2.5 – 23.2 years) with 13 females and 6 males. The cohort included 2 patients with platelet disorders, 5 patients with von Willebrand disease and 12 patients with factor deficiencies (see table 1). Sixteen patients (84%) underwent tonsillectomy and adenoidectomy, while 3 patients (16%) underwent tonsillectomy only. Pre-operative treatment in the form of coagulation factor infusion (with a goal of 100% factor levels prior to surgery) or DDAVP was given to 16 patients (84%). Nine patients (47%) received anti-fibrinolytic agent, aminocaproic acid, starting pre-operatively for an average of 15.5 days (Range 10 – 36 days) post-operatively. Six patients (32%) received aminocaproic acid only post-operatively for an average of 12 days (Range 7-14 days). One patient received Tranexamic acid for 19 days. Intraoperative hemostasis was achieved by electrocautery in 16 patients (84%) and coblation technique in 2 patients (10%). Surgical hemostasis technique for 1 patient was undocumented, however this patient did not have any bleeding complications subsequently. Ten patients (53%) experienced post-operative hemorrhage including 2 patients (10%) with early (<24 hours) bleeding and 8 patients (42%) with delayed (>24 hours) bleeding from surgical site. Bleeding resolved spontaneously in 2 patients while 8 patients (42%) required interventions such as cauterization (4 patients), extended aminocaproic acid dosing (4 patients), DDAVP (1 patient), DDAVP and tranexamic acid (1 patient), recombinant factor VII (1 patient), Humate-P® (1 patient), Factor VIII infusion (1 patient) and Factor IX infusion (1 patient). Three patients (30% of bleeding patients) required transfusions including 1 patient that received platelet transfusions, 1 patient received PRBCs and another patient received FFP. Recurrent bleeding was noted in 3 patients and the rate was significantly higher in older patients amongst those with bleeding complications (p=0.0189).Table 1Age (years, months)GenderDiagnosisSeverity of diseasePost-operative bleeding (Early ≤ 24 hours, Delayed >24 hours)Recurrent bleeding14,5MEssential ThrombocythemiaModerateEarlyYes13,6MFactor VII deficiencyMildDelayedNo6,7FFactor VII deficiencyMildDelayedNo7,6FFactor VII deficiencyMildNo-11,2FFactor XI deficiencyMildEarlyNo8,4MHemophilia ASevereDelayedNo9,4FHemophilia A carrierMildDelayedNo15,2FHemophilia A carrierMildNo-5,0MHemophilia BMildNo-23,2MHemophilia BMildDelayedYes6,1FHemophilia B carrierMildNo-6,8FHemophilia B carrierMildNo-15,2FHemophilia B carrierMildNo-11,4FMay-Hegglin anomalyModerateDelayedNo4,0FType 1 von WillebrandMildDelayedNo13,5FType 2A von WillebrandModerateDelayedYes2,5MType 2A von WillebrandModerateNo-9,9FType 2B von WillebrandModerateNo9,1FType III von WillebrandSevereNo- The rate of bleeding complications in pediatric patients with mild bleeding disorders undergoing adenotonsillectomy has been reported to be similar to that of normal population. In our cohort, delayed bleeding was more common than early bleeding consistent with current literature. We observed a higher rate of bleeding complications (53%) than reported in literature despite aggressive hemostatic support and adequate surgical techniques; however, our sample size was limited. Although there was no association between delayed hemorrhage and age, recurrent bleeding was associated with older age. We conclude that patients with bleeding disorders undergoing adenotonsillectomy are at a higher risk of bleeding and require close monitoring with hemostatic support for a prolonged period of time in post-operative period. Disclosures: No relevant conflicts of interest to declare.

Introduction Patients with inherited and acquired platelet disorders (PD) frequently present with thrombocytopenia and/or mucocutaneous bleeding. Diagnosis of PDs relies on both clinical and laboratory investigation, which encompasses both routine and esoteric platelet testing. The former includes platelet indices, light transmission aggregation (LTA) and platelet function analyzer (PFA-100). The latter includes platelet glycoprotein (GP) assessment by flow cytometry and platelet transmission electron microscopy (PTEM). Several recent studies have demonstrated limited sensitivities of routine platelet testing. It is uncertain if a combination of both routine and esoteric testing can vastly improve the sensitivity. Our goal is to assess the value of platelet esoteric testing and the ultimate sensitivity of laboratory platelet testing in diagnosing PDs. Methods Patients (between year 2012 and 2015) with a known or suspected inherited or acquired platelet disorders were recruited for platelet routine and esoteric testing. Patients' clinical features including ISTH bleeding assessment tool (BAT) scores, platelet count, LTA, PFA-100 ADP (CADP) and epinephrine (CEPI) cartridge closure times, GP expression by flow cytometry and PTEM were performed. All clinical and laboratory variables were collected and statistically analyzed. Results A total of 69 patients (51 females; median age 40 years; range: 8 months to 76 years) were enrolled to this cohort study. By retrospective chart review, 34 patients (49%) had a positive ISTH-BAT score (range 0 to 16). The most common bleeding manifestations (on any degree of severity) were cutaneous bleeding present in 53% of patients (n=37), menorrhagia in 47% of females (n=24), epistaxis in 36% (n=25) and postoperative bleeding in 35% (n=24). Joint, muscle and CNS hemorrhage were the least frequent with 7%, 6% and 1% of patients reporting bleeding in these sites. A total of 22 patients (32%) had thrombocytopenia at the time of their evaluation. Fifty-eight patients (84%) had platelet aggregation studies and of those 15 (26%) had an abnormal study. PFA-100 was performed in 57 patients (83%) of whom 42% (n=24) had prolonged closure times with either ADP or epinephrine. PTEM was performed on all samples. Twenty-seven patients (39%) had abnormal platelet structure including 17 patients who had dense granule deficiency. GP by flow cytometry was performed in 41 patients (59%) and abnormal glycoprotein expression was detected in 6 patients (15%). Of the 55 patients who had all tests performed, 22 patients (40%) had completely normal results. Of the routine tests, only PFA-CEPI or -CADP prolongation is associated with the likelihood of a PTEM abnormality (P<0.005). With the assistance of molecular testing, there were 2 cases of MYH-9 mutation-related platelet disorders, one of RUNX1 mutation-associated thrombocytopenia, one of York platelet syndrome, two of Bernard Soulier variants, one of Quebec syndrome and three of gray platelet syndrome or variants. Bleeding scores showed no statistically significant association with severity of any laboratory abnormalities. Conclusion In this cohort, the sensitivity of routine platelet testing in clinically suspected PDs is about 30-40%. Addition of platelet esoteric testing improves the sensitivity to 60%. However, the degree of platelet laboratory abnormalities do not predict severity of bleeding. The findings of this cohort underscore the importance of clinical assessment and both platelet routine and esoteric testing in investigation of patients with suspected PDs. Disclosures No relevant conflicts of interest to declare.

Abstract Background: Pediatric Anti-Phospholipid Syndrome (APS) is the most commonly acquired state of hypercoagulability in children, and is defined by venous and/or arterial thrombosis in the presence of circulating anti-phospholipid antibodies (aPLs) (most commonly lupus anticoagulant (LA), anticardiolipin antibody (aCL) and anti-β2-glycoprotein antibody (aβ2GP)). Catastrophic APS (CAPS) is a rare manifestation of APS, with thrombosis of multiple vessels that can lead to multi-system organ failure. Purpose: To determine the thromboses outcomes and factors predisposing to the risk of thrombotic recurrence in pediatric patients with a diagnosis of APS. Methods: Retrospective review of patients between the ages of 0-21 years diagnosed and treated with APS from 1997-2013 at our institution. Clinical data and long-term outcomes of these patients were reviewed. Exclusion criteria included neonatal APS and thrombosis with fetal loss. Statistical tests were performed using JMP software (© 2014 SAS Institute Inc., North Carolina, US). Associations between categorical variables were tested using chi-square test or Fisher’s exact test when required. Differences were considered statistically significant if p<0.05. Results: The study identified 23 patients (12 female; 11 male). Three patients with CAPS were identified and excluded from the analysis (3 female). Gender distribution for primary and secondary APS was similar (5 female/6 male primary APS; 4 female/5 male secondary APS). The median follow up period was 3.2 years (range; 0.01 – 16.87 years ). Median age at diagnosis of first episode of thrombosis was 16.16 years (range; 6.05 – 20.6 years). Nine patients (45%) with secondary APS had underlying autoimmune disease or malignancy (7 systemic lupus erythematosus, 1 ulcerative colitis, 1 Non-Hodgkin Lymphoma) and the remaining 11 patients were diagnosed as primary APS. Arterial and venous thrombosis occurred as the first thrombotic event in 7 (35%) and 13 (65%) patients, respectively. Lower extremity deep vein thrombosis (DVT) was the most frequent thrombotic event 11/20 (55%), followed by pulmonary embolism 7/20 (35%), ischemic stroke 4/20 (20%), lower extremity arterial thrombosis 3/20 (15%), upper extremity DVT 2/20 (10%), and IVC thrombosis 2/20 (10%). Recurrent or progressive thrombotic events occurred in 12/20 patients (60%). Of those, 7 were venous (58%), 5 were arterial (42%). At the time of recurrence, 3 patients were fully anticoagulated, (INR 2.5-3.5) versus 9 who were subtherapeutic (INR<2.0). Recurrent/progression thrombotic events occurred at the original site of thrombosis in 8 patients (3 arterial, 5 venous) while the remaining 4 recurrent thrombotic events occurred at other sites than the primary site. Overall venous and arterial thrombotic events were no different among primary or secondary APS (p=0.88). Thrombosis recurrence/progression risk at the original site or distant site was no different among primary or secondary APS (p=0.22 and p=0.30 respectively). Risk of recurrence/progression was not associated with subtherapeutic levels of anticoagulation (p=0.08), or presence of residual thrombosis at primary site at the time of recurrence (p=0.48). Conclusion: Recurrence and/or progression of thrombosis in APS occurred in 60% of the patients in our cohort, with 25% of the thrombosis recurrences occurring despite documented therapeutic anticoagulation in these patients. In contrast to other studies, our APS cohort demonstrated a higher rate of recurrence with other groups reporting thrombosis rates of recurrence such as 19-25%. Our cohort demonstrated similar rates of primary and secondary APS among female patients, in contrast to other studies suggesting higher rates of secondary APS in females. Potential risk factors such as primary versus secondary APS, subtherapeutic anticoagulation, and residual thrombosis from primary thrombotic event were not found as significant risk factors for thrombosis recurrence. Larger pediatric APS studies are needed in order to address other potential risk factors for thrombosis (ie obesity, inherited thrombophilia, intensity of anticoagulation, immune suppression approach for secondary APS), in order to establish treatment strategies for the prevention of recurrent thrombosis. Disclosures No relevant conflicts of interest to declare.

Abstract Background Congenital/hereditary qualitative platelet disorders (CQPD) can be classified by platelet count (eg, normal or decreased) and platelet size as well as by functional defect. Based on mean platelet volume (MPV), congenital thrombocytopenias (CT) are classified as macro-thrombocytopenias (eg, Bernard-Soulier syndrome [BSS], MYH-9 [myosin heavy chain 9, non-muscle]-associated thrombocytopenias, gray platelet syndrome [GPS], etc.); microthrombocytopenias (eg, Wiskott-Aldrich syndrome and variants); and those with normal platelet size. CQPDs with normal platelet count include Glanzmann thrombasthenia (GT), dense granule storage pool disorders (DG-SPD) including Hermansky-Pudlak syndrome (HPS), platelet secretion disorders and many others. Diagnosis has relied on platelet counting and sizing, blood smear light microscopy, platelet aggregation (agg) and platelet function analyzer (PFA-100) studies. Platelet transmission electron microscopy (PTEM) and flow cytometry can provide supplementary information and molecular analysis is also evolving. The objective of this study was to determine the roles of platelet transmission electron microscopy (PTEM) and flow cytometry in the diagnosis of CQPD and CT. Methods In this retrospective cohort study, after IRB approval, the electronic medical record system was queried for patients (pt) with a confirmed CQPD or CT seen at Mayo Clinic between 2000 and 2015. A detailed chart review was undertaken. Results 54 pt (64% female) met our study criteria; median age was 32 years (range 1 day to 81 years). 18/54 (33%) pt had macrothrombocytopenia: BSS 4 (7%); MYH-9 10 (19%); gray platelet syndrome 4 (7%). 36/54 (66%) had normal MPV: Glanzmann thrombasthenia 6 (11%); storage pool disorders including DG-SPD 10 (19%) and HPS 2 (3%), mild alpha granule deficiency 3 (6%) and York platelet syndrome 4 (7%); platelet secretion disorders 4 (7%); ANKRD26 mutation 3 (6%); congenital amegakaryocytic thrombocytopenia 1 (2%); GATA-1 mutation 1 (2%); RUNX-1 mutation 1 (2%); and Jacobsen syndrome 1 (2%). 44 pt (81%) had a positive bleeding history: epistaxis 52%, cutaneous bleeding 57%, gastrointestinal bleeding 21% and menorrhagia 54%; 10 pt (19%) had a negative bleeding history. Results of standard and esoteric platelet testing are summarized in Table 1. Diagnosis in the 10 pt with glycoprotein deficiency (BSS or GT) was established by agg; flow cytometry was confirmatory but not necessary. Of the 23 pt with SPD, 5 had a negative bleeding history; 4 pt had normal agg and PFA-100 and were diagnosed exclusively by PTEM. In this group, the abnormalities on platelet aggregation and PFA were variable and PTEM allowed for a better definition of the specific abnormalities. For MYH-9 patients, PTEM confirmed leukocyte inclusions that had already been identified on light microscopy. PTEM was the only diagnostic modality able to identify the abnormality in York platelet syndrome. In 5/54 (9%) genetic testing was necessary for diagnosis (GATA-1, ANKRD26 and RUNX-1) Conclusion In this cohort, standard platelet assays established the diagnosis in the large majority of CQPD and CT. PTEM was essential for confirmation in DG-SPD, mild alpha granule deficiency and York platelet syndrome and useful in combination with molecular testing to establish a diagnosis in selected cases. Guidance on selection of patients for such specialized testing requires further study. Table 1. Results of standard and esoteric platelet testing for 54 patients with congenital qualitative platelet disorders and/or thrombocytopenia Disorder n (%) Platelet aggregation PFA PTEM Flow cytometry Confirmation by genetics Done Abnormal Done Abnormal Done Abnormal Done Abnormal Glanzmann thrombasthenia 6 (11) 6 6 5 5 1 0 3 3 0 Bernard-Soulier syndrome & variants 4 (7) 4 4 4 4 3 0 4 4 0 MYH-9 related disorders 10 (19) 7 2 8 3 5 5 4 2 5 Dense granule deficiency and HPS 12 (22) 12 8 12 8 12 12 4 0 0 Alpha granule deficiency* 7 (13) 7 4 7 6 7 7 4 4 1 York platelet syndrome 4 (7) 1 0 1 1 4 4 1 1 0 TXA2 or PG synthesis/receptor defect 4 (7) 4 4 4 3 3 0 3 0 0 CATM 1 (2) 0 - 0 - 0 - 0 - 1 ANKRD26 3 (6) 3 3 3 2 3 3 3 3 3 GATA-1 1 (2) 0 - 1 1 1 1 1 1 1 RUNX-1 1 (2) 1 0 1 1 0 - 0 - 1 Jacobsen syndrome 1 (2) 1 0 1 1 1 1 1 0 1 MYH-9: myosin heavy chain 9, non-muscle (MHY-9) associated thrombocytopenia, HPS: Hermansky-Pudlak Syndrome, TXA2: thromboxane A2, PG: prostaglandin CATM: congenital amegakaryocytic thrombocytopenia. * Includes gray platelet syndrome Disclosures Pardanani: Stemline: Research Funding.

Abstract Background: Aortic stenosis-associated acquired von Willebrand syndrome (AS-AVWS) is caused by an accelerated degradation of the highest molecular weight von Willebrand factor (VWF) multimers (HMWM). We recently reported that the severity of the HMWM loss correlates with the severity of AS and patients’ bleeding tendency (Am J Cardiol, 2013;111:374-81). As for the missing HMWM, it is still uncertain if they are cleared from circulation or redistributed with medium-low MWMs, which can be assessed by VWF propeptide (Pro)/antigen (Ag) ratio. Besides the tedious VWF multimer analysis, it is uncertain if VWF activity by immunoturbidic method (Lx)/ Ag ratio or VWF collagen binding activity (CBA)/Ag ratio can be used as a screening test to predict AS-AVWS. It has been speculated in the literature that VWF:CBA is more sensitive than VWF:Lx for detecting a HMWM loss. Our goal was to exam the laboratory characteristics of various VWF tests in evaluating AS-AVWS and the potential mechanism of HMWM loss. Method: Sixty-six patients (between years 2010-2012, 43% male) with varying degrees of AS (16 mild, 20 moderate, and 30 severe) and separate 21 patients who had aortic valve replacement were assessed with VWF:Ag, VWF:Lx, VWF:CBA, platelet function analyzer collagen plus adenosine diphosphate (PFA-CADP), VWF multimer analysis and multimer ratio by densitometry (Am J Cardiol, 2013;111:374-81) after their echocardiography. The clinical endpoints of this study are AS severity measured by mean gradient (MG) by echocardiography and clinically significant bleeding. Statistical analyses including Spearman rank correlation test, estimation of the area under the receiver operating characteristics (ROC) curve, and Wilcoxon rank sum tests were performed. Results: VWF:Lx and VWF:CBA had strong correlation (Spearman r=0.94, P<0.001), and the correlation of VWF:CBA/Ag and VWF:Ltx/Ag was 0.49, p<0.001). As previously published, in patients with AS, MG correlated with VWF:Lx/Ag (Spearman r = -0.41, p <0.001), PFA-CADP (r = 0.49, p <0.001), and VWF multimer ratio (r = -0.76, p <0.001). MG also correlated with VWF:CBA/Ag (r= -0.38, p=0.002), but not with VWF: Pro/Ag (r=-0.20, p=0.12). Among AS and AVR patients, the area under the ROC curve for detection of the loss of HMWM was 0.88 (95% CI: 0.80-0.95) by VWF multimer ratio, 0.76 (95% CI: 0.65-0.86) by PFA-CADP, 0.70 (95% CI: 0.58-0.82) by VWF:CBA/Ag ratio, 0.67 (95% CI: 0.56-0.70) by VWF:Lx/Ag ratio, and 0.53 (95% CI: 0.41-0.65) by VWF:Pro/Ag . In addition to previously published results, clinically significant bleeding, in 14% of AS patients, was not associated with VWF:CBA/Ag (p=0.25) or VWF:Pro/Ag ratio (p=0.83). VWF: CBA/Ag ratio was significantly lower in patients with severe AS (MG > 40 mmHg) compared to AVR patients (median: 0.84 vs. 1.06, p<0.001), while there was no evidence of a difference in VWF:Pro/Ag (p=0.45). Conclusion: HMWM losses are highly prevalent in patients with moderate to severe AS. Of the VWF tests, PFA-CADP and VWF multimer analysis and ratio had the highest predictive ability for AS-AVWS followed by VWF:CBA/Ag and VWF:Lx/Ag. The VWF:CBA is not overly superior than VWF:Lx for predicting a HMWM loss. The normal VWF:Pro/Ag suggests that AS-AVWS is different from other types of AVWS due to accelerated clearance of HMWM. Disclosures No relevant conflicts of interest to declare.

The risk of viral infections and reactivation occurring in the setting of pediatric allogeneic hematopoietic stem cell transplantation is a concern in the pediatric patient, especially with the use of Alemtuzumab (Campath) as a conditioning agent. The purpose of this study was to determine the incidence of Epstein-Barr virus posttransplant lymphoproliferative disorder (EBV-PTLD), cytomegalovirus (CMV), and adenovirus among pediatric recipients of alemtuzumab at our institution. We found that EBV-PTLD occurred in 2.1% of transplants (1 matched unrelated donor [MUD] recipient), CMV reactivation occurred in 12.5% of transplants (4 MUD and 2 matched related donor [MRD] recipients) with disseminated CMV in 2.1% of cases (1 MRD recipient), and adenovirus infection occurred in 8.3% of the total transplants (2 MUD and 2 MRD recipients). Alemtuzumab continues to be used as a method of graft-versus-host disease and graft failure prevention among pediatric recipients of hematopoietic stem cell transplantation and seems to be safer than previously reported. At our institution, alemtuzumab has not increased the risk for EBV-PTLD, CMV infection, or adenovirus.

Abstract Rates of venous thromboembolism have increased in the adolescent population over the last two decades, likely due to advanced diagnostics, increased use of central venous catheters, chronic medical conditions, obesity, and oral contraceptive use. Of these factors, a modifiable risk factor for adolescents is obesity. Sedentary lifestyle and prolonged immobilization are additional prothrombotic risk factors that are often associated with obesity. With ever‐increasing screen time, sedentary behavior has risen accordingly, especially among gamers. We present four cases of adolescents who developed life‐threatening venous thromboembolic events in the setting of obesity, sedentary lifestyle and/or immobilization, and prolonged video game use.