In childhood, two distinct patterns of LAHS are observed, either associated with infection or autoimmune disease. Initial diagnostic investigations are critical to differentiating these two patterns as the prognosis and outcome for each is distinct.

Patients critically ill with COVID-19 are at risk for thrombotic events despite prophylactic anticoagulation. Impaired fibrinolysis has been proposed as an underlying mechanism. Our objective was to determine if fibrinolysis stimulated by tissue plasminogen activator (tPA) differed between COVID patients and controls. Plasma from 14 COVID patients on prophylactic heparin therapy was obtained and compared with heparinized plasma from 14 different healthy donors to act as controls. Kaolin activated thromboelastography with heparinase was utilized to obtain baseline measurements and then repeated with the addition of 4 nM tPA. Baseline fibrinogen levels were higher in COVID plasma as measured by maximum clot amplitude (43.6 ± 6.9 mm vs. 23.2 ± 5.5 mm, p < 0.0001) and Clauss assay (595 ± 135 mg/dL vs. 278 ± 44 mg/dL, p < 0.0001). With the addition of tPA, fibrinolysis at 30 min after MA (LY30%) was lower (37.9 ± 16.5% vs. 58.9 ± 18.3%, p = 0.0035) and time to 50% lysis was longer (48.8 ± 16.3 vs. 30.5 ± 15.4 min, p = 0.0053) in the COVID-19 samples. Clotting times and rate of fibrin polymerization (‘R’ or ‘α’ parameters) were largely the same in both groups. Clot from COVID patients contains a higher fibrin content compared to standard controls and shows resistance to fibrinolysis induced by tPA. These findings suggest the clinical efficacy of thrombolytics may be reduced in COVID-19 patients.

Background: Monitoring therapy in hemophilia is a major challenge. Measurement of factor levels is time consuming and not available in time to make clinical decisions. With the introduction of extended half-life factor products, determination of treatment frequency becomes important. Global hemostatic assays such as Thrombelastography (TEG) and Thrombin Generation Assay (TGA) may improve monitoring. Focused toward individualizing therapy, these assays may help determine treatment frequency based not just on Factor VIII PK (pharmacokinetic), but also on total hemostatic potential. Objective: To determine the correlation between TGA and TEG parameters, and Factor activity and half-life (t1/2). Design/Methods: With IRB approval and participant consent baseline FVIII activity was obtained at enrollment, 15minutes, 1, 4, 8, 24 and 48 hours post factor replacement in patients who had not received replacement factor for a minimum of 72 hours and were not bleeding. FVIII:C, TEG, and TGA at each time point were measured. Non-compartmental PK analysis was performed on each individual patient profile to measure Factor VIII terminal half-life (t 1/2), mean normalized factor clearance rate and volume of distribution at steady-state (Vdss). Pearson correlation statistical analyses on other variables were performed using JMP ¨ Pro version 12.0.1 (SAS Institute, Cary, NC, USA) Results: 27 patients with hemophilia have enrolled, with a median age of 14 years (range: 2-24 years). 9 patients were eliminated from analysis because of a diagnosis of inhibitors (n=1), factor activity >1% (n=4), inadequate sample collection (n=2), patient on episodic factor replacement (n=1), and inaccurate TGA time point (n=1). The mean Factor level prior to factor administration, after elimination of the subjects (n=18) was 0.4%. As expected, our results indicate a rise in ETP and Factor activity following factor replacement, peaking at 15 minutes post infusion. The mean normalized factor clearance rate was 3.3 ± 1.2ml/h/kg. The Vdss was 2.3 ± 1 L and Factor VIII t½ was 11.5 ± 3 hours. There were strong correlations between ETP and FVIII:C (R2=0.65; p<0.0001), Peak and FVIII:C (R2=0.6; p<0.0001), R Time and Factor VIII:C (R2=0.71; p<0.0001), Peak and R Time (R2=0.59; p<0.0001), ETP and R Time (R2=0.51; p<0.0001) as shown in table 1. Table 1. Correlation data on Factor VIII:C with TGA & TEG Parameters; and TGA parameters with TEG R time R2 P-value TGA Parameters (Peak & ETP) ETP and Factor VIII:C 0.65 p<0.0001 Peak and Factor VIII:C 0.60 p<0.0001 TEG Parameter (R Time) R Time and Factor VIII:C 0.71 p<0.0001 TEG and TGA Parameters Peak and R Time 0.59 p<0.0001 ETP and R Time 0.51 p<0.0001 Conclusions: Global hemostatic assays are less expensive than traditional PK testing and are available at the time of care decisions. Results of global coagulation assays (TEG and TGA) correlated closely with FVIII activities. Global assays may predict breakthrough bleeding independent of factor levels, representing an improvement in monitoring over traditional PK. With the emergence of the bioengineered extended half-life factor products, there is a renewed interest in pharmacokinetic analysis and individualization of therapy. Assays like TEG provide the opportunity to receive feed back in real time that corresponds to FVIII activity, and enable us to make treatment decisions rapidly for each individual patient. Since these assays measure more than just the factor activity, the parameters such as ETP on TGA may be more prognostic of bleeding tendency, as has been shown previously. Pharmacokinetic and pharmacodynamics analysis of this data is ongoing. Our small sample size precludes us from making global predictions. Larger multi center trials would assist in confirming these findings. Disclosures No relevant conflicts of interest to declare.

BackgroundPlatelet function testing to monitor antiplatelet therapy is important for reducing thromboembolic complications, yet variability across testing methods remains challenging. Here we evaluated the agreement of four different testing platforms used to monitor antiplatelet effects of aspirin (ASA) or P2Y12 inhibitors (P2Y12-I).MethodsBlood and urine specimens from 20 patients receiving dual antiplatelet therapy were analyzed by light transmission aggregometry (LTA), whole blood aggregometry (WBA), VerifyNow PRUTest and AspirinWorks. Result interpretation based on pre-defined cutoff values was used to calculate raw agreement indices, and Pearson's correlation coefficient determined using individual units of measure.ResultsAgreement between LTA and WBA for P2Y12-I-response was 60% (r = 0.65, high-dose ADP; r = 0.75, low-dose ADP). VerifyNow agreed with LTA in 75% (r = 0.86, high-dose ADP; r = 0.75, low-dose ADP) and WBA in 55% (r = 0.57) of cases. Agreement between LTA and WBA for ASA-response was 45% (r = 0.09, high-dose collagen WBA; r = 0.19, low-dose collagen WBA). AspirinWorks agreed with LTA in 60% (r = 0.32) and WBA in 35% (r = 0.02, high-dose collagen WBA; r = 0.08, low-dose collagen WBA) of cases.ConclusionsOverall agreement varied from 35 to 75%. LTA and VerifyNow demonstrated the highest agreement for P2Y12-I-response, followed by moderate agreement between LTA and WBA. LTA and AspirinWorks showed moderate agreement for aspirin response, while WBA showed the weakest agreement with both LTA and AspirinWorks. The results from this study support the continued use of LTA for monitoring dual antiplatelet therapy, with VerifyNow as an appropriate alternative for P2Y12-I-response. Integration of results obtained from these varied testing platforms with patient outcomes remains paramount for future studies.