A single-institution retrospective study of causes of prolonged prothrombin time and activated partial thromboplastin time in the outpatient setting.

INTRODUCTION: An algorithmic approach, termed the prolonged clot time profile (PROCT), consisting of initial screening with prothrombin time (PT) and activated partial thromboplastin time (aPTT), reflexive mixing studies if indicated, and follow-up assays depending on initial testing results, offers an efficient approach to delineate the etiology of a prolonged PT/aPTT. Herein, we present the outcomes of the PROCT in the outpatient setting. METHODS: In this retrospective study, we reviewed medical records of consecutive outpatients who had prolonged PT and/or aPTT noted in the routine coagulation laboratory and who had PROCT ordered in our institutional Special Coagulation Laboratory between 2010 and 2017. RESULTS: One hundred and six patients, median age 55 years (IQR 30-67), met our study criteria. Twenty-nine patients had normal PT/aPTT, while 77 had persistent abnormalities and underwent reflexive testing. A prolonged PT, aPTT, or PT and aPTT was noted in 27 (35%), 27 (35%), and 23 (30%) respectively. Forty-nine (64%) had an acquired condition, 17 (22%) had a congenital condition, 7 (9%) had unclear etiology, and 4 (5%) were the result of laboratory artifact. The most common known cause of an isolated prolonged PT in our study was vitamin K deficiency in 8 (10%), the most common cause of an isolated prolonged aPTT was lupus anticoagulant in 4 (5%), and the most common cause of prolonged PT and aPTT was liver disease in 11 (14%). CONCLUSION: Prolonged PT/aPTT have a wide range of causes, including artifactual prolongation or abnormalities in secondary hemostasis due to both inherited and acquired conditions.

Reflex factor coagulation testing in patients with an unexplained prolonged aPTT: An institutional retrospective review.

BACKGROUND: We aim to determine the clinical utility of reflex coagulation investigations (RCI) for prolonged lupus insensitive activated partial thromboplastin time (aPTT) at our institution. METHODS: We retrospectively reviewed all potential RCI (lupus insensitive aPTT of ≥32s) from April 2014 to June 2019. Our diagnostic algorithm requires completion of RCI only if samples had no interfering medications to explain a prolonged aPTT and were either from a preoperative sample or from a patient presenting with unexplained bleeding. Appropriate RCI samples undergo further investigations with one-stage factor activity testing for factors 8(FVIII), 9(FIX), and 11(FXI) reflexively. Data were obtained through electronic medical records to capture clinical characteristics, laboratory findings, prophylactic hemostatic replacement, and bleeding outcomes. RESULTS: Three thousand and three hundreds seventeen samples from 2940 distinct patients were considered as potential RCI during the study period. 263/3317 (8%) samples had RCI completed. Of those, 55/263 (21%) had abnormal factor testing, with the majority from preoperative setting (43/55; 78%). 5/43 (12%) patients were referred to hematology for preoperative evaluation. 5/43 patients received preoperative hemostatic support. A total of 5 patients (5/43) developed postop bleeding. Six patients (6/55) had RCI for unexplained bleeding, and five patients (83%) had a newly identified clinically significant bleeding disorder. CONCLUSION: Reflex coagulation investigations benefited patients presenting with unexplained bleeding as this expedited the diagnosis and management of clinically significant bleeding disorders. RCI for preoperative evaluation infrequently led to additional hemostatic support/referral to hematology. The lack of additional workup for an abnormal factor activity level suggests laboratory alert fatigue as a potential contributory factor.

Caution in Using the Activated Partial Thromboplastin Time to Monitor Argatroban in COVID-19 and Vaccine-Induced Immune Thrombocytopenia and Thrombosis (VITT).

INTRODUCTION: Argatroban is licensed for patients with heparin-induced thrombocytopenia and is conventionally monitored by activated partial thromboplastin time (APTT) ratio. The target range is 1.5 to 3.0 times the patients' baseline APTT and not exceeding 100 s, however this baseline is not always known. APTT is known to plateau at higher levels of argatroban, and is influenced by coagulopathies, lupus anticoagulant and raised FVIII levels. It has been used as a treatment for COVID-19 and Vaccine-induced Immune Thrombocytopenia and Thrombosis (VITT). Some recent publications have favored the use of anti-IIa methods to determine the plasma drug concentration of argatroban. METHODS: Plasma of 60 samples from 3 COVID-19 patients and 54 samples from 5 VITT patients were tested by APTT ratio and anti-IIa method (dilute thrombin time dTT). Actin FS APTT ratios were derived from the baseline APTT of the patient and the mean normal APTT. RESULTS: Mean APTT ratio derived from baseline was 1.71 (COVID-19), 1.33 (VITT) compared to APTT ratio by mean normal 1.65 (COVID-19), 1.48 (VITT). dTT mean concentration was 0.64 µg/ml (COVID-19) 0.53 µg/ml (VITT) with poor correlations to COVID-19 baseline APTT ratio r2 = 0.1526 p <0.0001, mean normal r2 = 0.2188 p < 0.0001; VITT baseline APTT ratio r2 = 0.04 p < 0.001, VITT mean normal r2 = 0.0064 p < 0.001. CONCLUSIONS: We believe that dTT is a superior method to monitor the concentration of argatroban, we have demonstrated significant differences between APTT ratios and dTT levels, which could have clinical impact. This is especially so in COVID-19 and VITT.

Hypercoagulation detected by routine and global laboratory hemostasis assays in patients with infective endocarditis.

BACKGROUND: Coagulation system is heavily involved into the process of infective endocarditis (IE) vegetation formation and can facilitate further embolization. In this study we aimed to assess the coagulation and platelet state in IE implementing a wide range of standard and global laboratory assays. We also aim to determine whether prothrombotic genetic polymorphisms play any role in embolization and mortality in IE patients. METHODS: 37 patients with IE were enrolled into the study. Coagulation was assessed using standard coagulation assays (activated partial thromboplastin time (APTT), prothrombin, fibrinogen, D-dimer concentrations) and integral assays (thromboelastography (TEG) and thrombodynamics (TD)). Platelet functional activity was estimated by flow cytometry. Single nuclear polymorphisms of coagulation system genes were studied. RESULTS: Fibrinogen concentration and fibrinogen-dependent parameters of TEG and TD were increased in patients indicating systemic inflammation. In majority of patients clot growth rate in thrombodynamics was significantly shifted towards hypercoagulation in consistency with D-dimers elevation. However, in some patients prothrombin, thromboelastography and thrombodynamics were shifted towards hypocoagulation. Resting platelets were characterized by glycoprotein IIb-IIIa activation and degranulation. In patients with fatal IE, we observed a significant decrease in fibrinogen and thrombodynamics. In patients with embolism, we observed a significant decrease in the TEG R parameter. No association of embolism or mortality with genetic polymorphisms was found in our cohort. CONCLUSIONS: Our findings suggest that coagulation in patients with infective endocarditis is characterized by general hypercoagulability and platelet pre-activation. Some patients, however, have hypocoagulant coagulation profile, which presumably can indicate progressing of hypercoagulation into consumption coagulopathy.

Incidence, and preoperative and intraoperative prognostic factors of deep venous thrombosis in patients with glioma following craniotomy.

OBJECTIVES: The aim of this study was to investigate the incidence of deep vein thrombosis (DVT) and the preoperative and intraoperative risk factors associated with DVT in glioma patients METHODS: We conducted a retrospective analysis of data obtained from glioma patients at Sanbo Hospital (Beijing, China) between 2018 and 2021. Symptomatic DVT was confirmed by Doppler ultrasonography. Multivariable logistic regression analysis was used to identify preoperative and intraoperative characteristics associated with DVT. Basic clinical variables and laboratory results were analyzed. RESULTS: A total of 492 glioma patients were included. Of these, 73 (14.84%) developed DVT, and three (0.61%) developed DVT and pulmonary embolism (PE). Multivariate analyses revealed that the following factors were highly predictive of post-operative DVT: older age ranges of 46--55 years (odds ratio [OR]: 2.94; 95% confidence interval [CI]: 1.41--6.13; p = 0.004), 56--65 years (OR: 7.86; 95% CI: 3.63--17.03; p < 0.001), and > 65 years (OR: 4.94; 95% CI: 1.83--13.33; p = 0.002); partial thromboplastin time (APTT; OR: 0.91; 95% CI: 0.84--1.00; p = 0.040); D-dimer (OR: 2.21; 95% CI: 1.28--3.82; p = 0.005); and surgery duration (OR: 2.87; 95% CI: 1.6 --5.07; p < 0.001) CONCLUSIONS: Older age, preoperative APTT, D-dimer, and surgery duration independently increased the risk of developing postoperative DVT. These findings may facilitate the development of a thrombosis risk score that will allow physicians to develop individualized strategies to prevent DVT as early as possible.

Prevalence and Clinical Impact of Reduced Coagulation Factor XII Activity in Patients Receiving Extracorporeal Membrane Oxygenation.

OBJECTIVES: Extracorporeal membrane oxygenation provides large surface exposure to human blood leading to coagulation activation. Only limited clinical data are available on contact activation and coagulation factor XII activity in extracorporeal membrane oxygenation patients. DESIGN: Prospective cohort study. SETTING: Three medical ICUs at the Medical University of Vienna. PATIENTS: Adult patients receiving venovenous or venoarterial extracorporeal membrane oxygenation. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The primary outcome was the change in coagulation factor XII activity in response to extracorporeal membrane oxygenation. Secondary outcomes included the prevalence of reduced coagulation factor XII activity (< 60%) among patients receiving extracorporeal membrane oxygenation and association of coagulation factor XII activity with thromboembolic and bleeding complications. An exploratory endpoint was the association of coagulation factor XII activity and activated partial thromboplastin time in heparinase-treated samples in vitro. Fifty-one patients with a total of 117 samples were included in the study between July 2018 and February 2020. Fifty patients (98%) had reduced coagulation factor XII activity at any timepoint during extracorporeal membrane oxygenation. Median coagulation factor XII activity during extracorporeal membrane oxygenation treatment was 30% (interquartile range, 21.5-41%) and increased after discontinuation (p = 0.047). Patients with thromboembolic complications had higher median coagulation factor XII activity during extracorporeal membrane oxygenation (34% vs 23%; p = 0.023). The odds of a thromboembolic event increased by 200% per tertile of median coagulation factor XII activity (crude odds ratio, 3.034; 95% CI, 1.21-7.63). No association with bleeding was observed. In heparinase-treated samples, coagulation factor XII activity correlated well with activated partial thromboplastin time (r = -0.789; p = 0.007). CONCLUSIONS: We observed a high prevalence of reduced coagulation factor XII activity in adult patients on extracorporeal membrane oxygenation, which may confound activated partial thromboplastin time measurements and limit its clinical usefulness for monitoring and titrating anticoagulation with unfractionated heparin. Lower coagulation factor XII activity was associated with less thromboembolic complications, which may highlight the potential of coagulation factor XII to serve as a target for anticoagulation in extracorporeal membrane oxygenation.

The Prognostic Role of Prothrombin Time and Activated Partial Thromboplastin Time in Patients with Newly Diagnosed Multiple Myeloma.

PURPOSE: To evaluate the prognostic role of prothrombin time (PT) and activated partial thromboplastin time (APTT) for newly diagnosed multiple myeloma (MM). METHODS: We retrospectively analyzed 354 patients with newly diagnosed MM who received primary treatment in our center. The propensity score matching technique was used to reduce the bias between groups. RESULTS: Among 354 patients, lengthened PT or APTT was observed in 154 (43.5%) patients and 200 (56.5%) patients had normal PT and APTT. Patients with lengthened PT or APTT had significantly shorter median overall survival (OS) (37.5 vs. 73.8 months, p < 0.001) and progression-free survival (PFS) (23.1 vs. 31.6 months, p = 0.001) than those with normal PT and APTT. Univariate Cox proportional hazards regression analyses showed that lengthened PT or APTT was associated with shorter OS (HR = 2.100, 95% CI: 1.525-2.893, p < 0.001). Lengthened PT or APTT was also a poor prognostic factor for OS (HR = 3.183, 95% CI: 1.803-5.617, p < 0.001) in multivariable analyses. The poor effect of lengthened PT or APTT on PFS was confirmed in univariate analysis (HR = 1.715, 95% CI: 1.244-2.365, p = 0.001), but it had no impact on PFS in multivariate analysis (p = 0.197). In the propensity score matching analysis, 154 patients, 77 in each group, were identified. Among 154 matched patients, the OS of patients with lengthened PT or APTT was shorter (38.4 vs. 51.0 months, p = 0.030), but PFS was similar (29.0 vs. 35.0 months, p = 0.248). CONCLUSION: These results demonstrated that lengthened PT or APTT was an independent poor prognostic factor for patients with newly diagnosed MM.

Vitamin K2 (Menaquinone-7) supplementation does not affect vitamin K-dependent coagulation factors activity in healthy individuals.

BACKGROUND: Vitamin K has long been regarded as a procoagulant drug by physicians, and concerns have been raised with regard to its effects on hemostasis. Although many studies have shown that vitamin K supplementation is safe for thrombotic events, the effect of vitamin K supplementation on the activities of vitamin K dependent procoagulation factors in healthy individuals is not available. OBJECTIVES: This study aimed to investigate whether vitamin K2 supplementation at recommended doses affects the activity of vitamin K dependent procoagulation factors in healthy individuals without any anticoagulation treatment. DESIGN: Forty healthy volunteers between 25 and 40 years of age were recruited. Menaquinone-7 (MK-7) was administrated at 90 µg for 30 days. Prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), and blood coagulation factors II, VII, IX, and X activities and Protein induced by vitamin K absence or antagonist-II (PIVKA-II) were measured on days 0 and 30 after MK-7 administration. RESULTS: PT, APTT, and TT showed no significant differences on day 30 when compared with baseline. The activities of coagulation factors II, VII, IX, and X on day 30 showed no significant differences with those at baseline. PIVKA-II levels were unchanged after 30 days of MK-7 supplementation. CONCLUSIONS: MK-7 supplementation at recommended dosage does not affect vitamin K-dependent coagulation factors' coagulation activity, and does not enhance the carboxylation of prothrombin in healthy individuals. This indicated that MK-7 administration does not alter hemostatic balance in healthy populations without anticoagulation treatment.

Applying index of circulating anticoagulant to mixing tests with lupus anticoagulant screen and confirm reagents can distinguish with high specificity between lupus anticoagulants and direct factor Xa inhibitors.

BACKGROUND: Lupus anticoagulants (LA) are detected by prolongation of clotting times for dilute Russell's viper venom time (dRVVT) and activated partial thromboplastin time (APTT) screening tests. Direct oral anticoagulants (DOACs) can interfere with both screening and confirmatory tests. The present study aimed to investigate the influence of direct factor Xa inhibitors (DiXaIs) on screen, confirm and mixing tests and establish a method for differentiation from other sample types. MATERIALS AND METHODS: A total of 257 samples including nonanticoagulated LA positive, LA positive with DiXaIs, factor deficiency, FVIII inhibitors, warfarin and non-APS DiXaIs were tested. APTT reagents Cephen LS/Cephen and dRVVT reagents LA1/LA2 were used, respectively, to screen/confirm the study group. Index of circulating anticoagulant (ICA) was calculated from clotting times based on the following formula as ICA screening and ICA confirmation. ICA= (1:1 Mix sample - Normal pooled plasma) / Screen patient x 100. An ICA matrix was established which suggested the presence of a DiXaI when both ICA screening and confirmation were above the cut-off. When only ICA screening is elevated, LA is suspected. RESULTS: Sensitivity and specificity of the ICA matrix were 52.2% and 92.8% for DiXaIs and 38.1% and 96.7% for LA in APTT, and 61.2% and 92.9% for DiXaIs and 22.2% and 88.4% for LA in dRVVT, respectively. CONCLUSION: The ICA matrix achieved high specificity with a lower apparent sensitivity for DiXaI samples comparatively to other devices but due only to less interferences: the matrix could contribute to differentiating DiXaIs from LA in samples where anticoagulation status is unknown.

Analytical Performance Evaluation of Automated Coagulation Analyzer CP3000 for Routine and Special Coagulation Assays.

CP3000 coagulation analyzer is a high-throughput, fully automated coagulation analyzer. The objective of this study was to evaluate the analytical performance of CP3000 coagulation system for general and special coagulation analyses. Quality control materials and patient samples were used to evaluate the analytical performance of CP3000 coagulation system. Precision, carryover, linearity, comparability with ACL-TOP 700 coagulation system, and verification of reference range were evaluated or performed according to Clinical and Laboratory Standards Institute guidelines. Within-run and between-run precisions were below 5% for both normal and abnormal ranges. There was no detectable carryover. The linearity of antithrombin and fibrinogen were excellent. The comparability between CP3000 and ACL-TOP 700 coagulation systems was acceptable except for activated partial thromboplastin time and thrombin time due to differences in reagent composition. Reference ranges proposed by the manufacturer were verified to be acceptable. CP3000 coagulation system is a reliable system that can be used to perform routine and special coagulation tests rapidly and accurately. Because of its small footprint as an additional advantage, the implementation of CP3000 coagulation system can be efficient in hospital laboratories of various sizes.

The Evaluation of APTT Reagents in Reference Plasma, Recombinant FVIII Products; Kovaltry® and Jivi® Using CWA, Including sTF/7FIX Assay.

The FVIII activity in patients treated with several extended half-life FVIII (EHL-FVIII) agents different when various activated partial thromboplastin time (APTT) reagents were used. The present study examined the difference in clot waveform analysis (CWA) findings and FVIII activity when various APTT reagents and CWA were used. The CWA including FVIII activity was measured using 12 APTT reagents, and the FIX activation based on a small amount of tissue factor assay (sTF/FIX) were examined in reference plasma (RP), EHL-FVIII (Jivi®) and Kovaltry®. The 3 APTT reagents were associated with high variation in the peak time and height in the CWA when analyzing low concentrations of FVIII. The peak time and height could not be measured with one APTT reagent, and there were marked differences in the CWA findings between Jivi® and Kovaltry® among APTT reagents. Several APTT reagents showed a markedly lower FVIII activity with Jivi® than with Kovaltry®. In the FVIII assay, the peak time measured with sTF/FIX did not differ markedly between Jivi® and Kovaltry®; however, the FVIII activity in Jivi® (as measured by the peak height) tended to be higher than in Kovaltry®. The CWA findings for monitoring Jivi® varied for monitoring Jivi® depending on the APTT reagents used, and sTF/FIX assay may be able to measure the EHL-FVIII.

Clinical utility of activated partial thromboplastin time clot waveform analysis and thrombin generation test in the evaluation of bleeding phenotype in Hemophilia A.

CONTEXT: Hemophilia A is classified as mild, moderate, and severe based on Factor VIII levels (FVIII). Clot-based assays only detect initiation of thrombin generation, hence FVIII levels may not accurately predict the bleeding risk in all hemophilia patients. The entire process of thrombin generation as measured by global hemostasis tests like activated partial thromboplastin time clot waveform analysis (APTT CWA) and thrombin generation test (TGT) may reflect the actual bleeding phenotype. AIMS: To assess the utility of TGT and CWA as a screening tool to identify bleeders and to evaluate the bleeding phenotype in Hemophilia A. SETTINGS AND DESIGN: Prospective, observational study of 147 consecutive patients referred for coagulation workup. SUBJECTS AND METHODS: Bleeding assessment tool was used to identify bleeders. Patients were classified as severe and nonsevere bleeders based on clinical criteria. TGT was performed by calibrated automated thrombogram, CWA by photo-optical coagulometer and factor levels by one stage clot-based assays. STATISTICAL ANALYSIS USED: The Kruskal-Wallis test with post-hoc analysis was done to examine the difference in CWA/TGT parameters amongst hemophilia classified by FVIII levels. Receiver operating characteristic (ROC) analysis was performed to estimate the diagnostic accuracy of CWA and TGT in discriminating between clinically severe vs nonsevere bleeders. RESULTS: Using ROC derived cut-offs of min1, min2 and peak height of thrombin (PH), the sensitivity (min1:91.67%, min2:91.67%, PH: 97.22%, FVIII: 86.11%) and specificity (min1:100%, min2:100%, PH: 90.91%, FVIII: 90.91%) of CWA/TGT was superior to FVIII to distinguish between clinically severe vs nonsevere bleeders. Phenotypic heterogeneity of bleeding severity was identified in our study population. Clinical severity correlated with CWA/TGT parameters instead of FVIII levels. CONCLUSIONS: CWA and TGT are more effective tools than conventional factor assays to identify clinically severe bleeders and tailor prophylaxis as per bleeding phenotype.

Revisiting the effects of spectral interfering substances in optical end-point coagulation assays.

INTRODUCTION: Hemolysis, icterus, and lipemia (HIL) are common pre-analytical variables in the clinical laboratory. Understanding their effects on coagulation laboratory results is essential. METHODS: HIL effects on the prothrombin time (PT), activated partial thromboplastin time (APTT), dilute Russell's viper venom time (DRVVT), thrombin time (TT), and protein C chromogenic activity (CFx) were evaluated on the ACL TOP 750 optical analyzer and STA-R Evolution mechanical analyzer (PT and APTT only) by spiking normal donor, patient, and commercial control samples with varying concentrations of hemolysate, bilirubin, or a lipid emulsion. The relative difference or bias compared to the original results was determined. RESULTS: Hemolysis (H) indices up to 900 mg/dL did not affect the APTT, PT, DRVVT Confirm, TT, and CFx; however, H indices above approximately 200 mg/dL resulted in a false-negative DRVVT screen and screen/confirm ratio in samples with a lupus anticoagulant. There was an artifactual prolongation of the PT and APTT when conjugated bilirubin was dissolved in aqueous solvents and not when it was dissolved in dimethyl sulfoxide. Icterus (I) indices up to 45 mg/dL did not result in significant (>15%) bias for all assays evaluated. The PT and APTT assays failed to produce a robust clot curve when the lipemia (L) index exceeded 6000 milliabsorbance units (mAbs), and the TT and DRVVT assays failed when the L index exceeded 3000 mAbs; the CFx assay was unaffected by lipemia. CONCLUSIONS: Verification of the manufacturer's recommended interference thresholds is important since it may avoid inappropriate instrument flagging and/ or sample rejection.

Overall hemostasis potential and aPTT-clot waveform analysis as powerful laboratory diagnostic tools for identification of hemophilia A patients with unexpected bleeding phenotype.

INTRODUCTION: Traditionally used laboratory methods do not always accurately reflect bleeding severity in hemophilia A (HA) patients. The ability of three global assays for identifying patients with unexpected bleeding phenotype was investigated. METHODS: Overall hemostasis potential (OHP), aPTT-clot waveform analysis (aPTT-CWA), endogenous thrombin potential (ETP), FVIII activities, and prothrombin fragment 1 + 2 concentrations were measured in 62 HA patients (30 severe and 32 non-severe) and 27 male controls. Bleeding phenotype was determined using our proposed scoring system including age at first joint bleed, number of target joints, and number of joint/muscle bleeds per year. Bleeding score ≤ 4 defined patients with mild bleeding phenotype (N = 27); score ≥ 5 defined severe bleeding phenotype (N = 35). RESULTS: The receiver operating characteristic analysis performed for distinguishing patients with severe and mild bleeding phenotype yielded following values of area under the curve: 0.910 (FVIII); 0.891 (aPTT-CWA parameter DELTA); 0.769 (OHP); and 0.634 (ETP). Unexpected bleeding phenotype was identified in 11/62 HA patients: 8/32 (25%) non-severe HA patients had severe, while 3/30 (10%) severe HA patients had mild bleeding phenotype, and global assays enabled the identification of all these patients. OHP and DELTA were revealed as the most reliable parameters for bleeding phenotype determination (10/11 and 9/11 unexpected results, respectively). CONCLUSION: This study emphasizes OHP and aPTT-CWA as a powerful laboratory diagnostic tool in identifying HA patients with unexpected bleeding presentations, with the best results achieved by combining both assays. Global assays should not completely replace FVIII activity measurement but should be a part of the HA diagnostic algorithm.

Effectiveness of a Calculation-Free Weight-Based Unfractionated Heparin Nomogram With Anti-Xa Level Monitoring Compared With Activated Partial Thromboplastin Time.

BACKGROUND: Accurate monitoring of intravenous unfractionated heparin (UFH) is essential to mitigate the risk of adverse drug events associated with dosing errors. Although recent data support anti-factor Xa (anti-Xa) monitoring preferentially over activated partial thromboplastin time (aPTT) to improve time to therapeutic anticoagulation, the utility of incorporating anti-Xa monitoring with a calculation-free weight-based UFH nomogram has not been formally evaluated. OBJECTIVE: The primary objective of this study was to evaluate the time to therapeutic anticoagulation of a calculation-free weight-based UFH nomogram integrated with anti-Xa monitoring versus a historical control of aPTT monitoring utilizing manual dose calculations. METHODS: This was a retrospective analysis of patients with anti-Xa monitoring and a novel calculation-free weight-based UFH nomogram compared with a historical control with aPTT monitoring and manual calculations. RESULTS: A total of 103 patients in the aPTT cohort and 100 patients in the anti-Xa cohort were analyzed. The anti-Xa cohort achieved goal therapeutic target 3.8 hours sooner than the aPTT cohort (P = 0.03). Patients with anti-Xa monitoring required 1 fewer adjustment per 2.5 patient-days of UFH with the venous thromboembolism nomogram (P = 0.02). Patients in the aPTT cohort required more infusion interruptions because of supratherapeutic values (P = 0.007) and boluses because of subtherapeutic values (P = 0.044). There were no differences in rates of thromboembolism, major bleeding, or clinically relevant nonmajor bleeding between the cohorts. CONCLUSION AND RELEVANCE: This study demonstrated that anti-Xa UFH monitoring integrated with a calculation-free nomogram results in faster time to therapeutic anticoagulation and fewer dose adjustments compared with aPTT monitoring with manual calculations.

Performance Assessment of a Multifaceted Unfractionated Heparin Dosing Protocol in Adult Patients on Extracorporeal Membrane Oxygenator.

BACKGROUND: The use of extracorporeal membrane oxygenator (ECMO) support devices are associated with complications, including bleeding and thrombosis. Unfractionated heparin (UFH) is the gold standard anticoagulant in ECMO patients. Clinically, UFH is monitored through activated clotting time (ACT), activated partial thromboplastin time (aPTT), and anti-factor Xa assay. It is unknown which assay best predicts anticoagulation effects in adults. OBJECTIVE: To assess the correlation of UFH dosing and monitoring using an established protocol. METHODS: A pilot, prospective cohort, historically controlled study was conducted at a tertiary care hospital. Patients ≥18 years-old who received ECMO on the multifaceted anticoagulation protocol were included and compared with those on the conventional method of anticoagulation. The primary end point was to assess the correlation between UFH dose and different monitoring methods throughout 72 hours using the new protocol guided by ACT and anti-factor Xa assay. RESULTS: In each arm, 20 patients were enrolled. The study revealed that anti-factor Xa assay had the largest number of "strong" correlations 11/20 (55%), followed by both aPTT and aPTT ratio 10/20 (50%), and, finally, ACT 2/20 (10%). Concordance between anti-factor Xa assay and the other monitoring parameters in the prospective arm was generally low: 31% with aPTT ratio, 26% with ACT, and 23% with aPTT. CONCLUSION AND RELEVANCE: The adaption of a multifaceted anticoagulation protocol using anti-factor Xa assay may provide a better prediction of heparin dosing in adults ECMO patients compared with the conventional ACT-based protocol. Further studies are needed to assess the safety and different monitoring modalities.

A Novel Assessment of Factor VIII Activity by Template Matching Utilizing Weighted Average Parameters from Comprehensive Clot Waveform Analysis.

BACKGROUND: Activated partial thromboplastin time (aPTT)-based clot waveform analysis is used to evaluate the comprehensive dynamics of fibrin clot formation. In addition, the technique can be usefully utilized for the rapid assessment of factor (F)VIII procoagulant activity in various clinical settings in patients with hemophilia A (HA). We defined a novel algorithm based on the weighted average parameters from aPTT-based waveforms to devise a template-matching procedure for assessing FVIII activity (FVIII:C). METHODS: The first derivatives of original clot waveforms triggered by the aPTT reagent (Coagpia APTT-N) were used to determine weighted averages of areas surrounded by the waveform at different percentages of maximum height in various clotting factor-deficient plasmas. Prepared templates based on 50 weighted average-related parameters were compared with 78 aPTT-prolonged plasmas. RESULTS: Original nonsmoothed waveforms of the various clotting factor-deficient plasmas with prolonged aPTTs demonstrated a variety of shapes. The weighted averages were calculated after adjustments for different baselines, and the patterns seemed to be governed by the specific clotting factor deficiency. The weighted average-related parameters including baseline wedge (r 2 = 0.998) and aspect ratio (r 2 = 0.998) were highly correlated with FVIII:C levels. Template-matching analyses based on weighted average-related waveform parameters obtained from 158 samples demonstrated that the sensitivity was 97.2% and specificity was 83.3% in aPTT-prolonged plasmas (n = 78). CONCLUSION: This novel algorithm based on weighted averages of aPTT-based waveforms together with template-matching may support clinical usefulness for judging of HA and may aid clinical management in the patients in the absence of specific clotting factor assays.

Microkinetic coagulation assays for human and zebrafish plasma.

Coagulation assays, prothrombin time (PT), and partial thromboplastin time (PTT) are tests to measure the clotting ability of plasma and used in evaluating patients suffering from bleeding disorders. These assays require 100 µl of human plasma. In zebrafish, dilute plasma with exogenously added human fibrinogen was used. Our objective is to create a microkinetic coagulation assay for human and zebrafish plasmas using 1 µl plasma under conditions similar to PT and PTTs. Here, we developed an assay using the Take3 plate with wells holding up to 6 µl, which can be loaded in a microplate reader for measuring the absorbance of fibrin formation. In this assay, we used 1 µl of citrated zebrafish or human plasma followed by the addition of either thromboplastin or Dade ACTIN or factor X activator from Russell viper venom as an activating agent and CaCl2. We found 4 or 3 µl of the final volume of reaction was optimal. Our results showed both zebrafish and human plasmas yielded kinetic PT, kinetic PTT, and kinetic Russel's viper venom time curves similar to previously established curves using dilute plasma. This kinetic coagulation was inhibited by heparin and was reduced significantly in coagulation factor deficient plasmas. These results validated our microkinetic coagulation assays. Moreover, we derived clotting times from these kinetic curves, which were identical to human PT, PTT, and Russel's viper venom time. In conclusion, we established a microkinetic assay that could measure blood coagulation activity in models like zebrafish and human blood samples obtained from a finger prick in adults or heel prick in infants.

The First-Derivative Curve of the Coagulation Waveform Reveals the Cause of aPTT Prolongation.

Clot waveform analysis based on activated partial thromboplastin time (aPTT) is reported to be a useful assay. We attempted to find beneficial parameters with the first-derivative curve. We examined 106 plasma samples with prolonged aPTT and analyzed the first-derivative curve statistically by dividing it into 6 groups (Lupus anticoagulant, Heparin, Direct oral anticoagulants, Factor VIII inhibitor, Hepatic dysfunctions and Factor deficiency). We obtained 7 coordinates for parameter measurement by analyzing the first-derivative curve and set 20 parameters including the velocity axis, the time axis, and area parameters. The distribution was checked by extracting each parameter that showed the most significant difference in the 6 groups. As a result, it was revealed that we could classify aPTT prolongation by using a combination of 3 parameters, the initial-to-peak gradient, the ratio initial-to-intermediate velocity/intermediate-to-peak velocity, and the initial-to-peak area size. We constructed a flowchart combining these 3 parameters and were able to discriminate 75% of the specimens. These parameters derived from the first-derivative curve of clot waveform analysis are useful tools to discriminate aPTT prolongation.

Effects of Emicizumab on APTT, FVIII assays and FVIII Inhibitor assays using different reagents: Results of a UK NEQAS proficiency testing exercise.

INTRODUCTION: Emicizumab (Hemlibra: Roche Switzerland) is a, humanized, bi-specific monoclonal modified immunoglobulin G4 (IgG4) which binds human FX, FIX and activated FIX (FIXa) to mimic activated FVIII activity. AIM: Evaluate the effects of emicizumab on the APTT, surrogate FVIII activity and FVIII inhibitor results. METHODS: Two samples were provided, one obtained from an emicizumab treated severe haemophilia A patient with FVIII inhibitors and one constructed by in vitro addition of emicizumab using plasma from a severe haemophilia A patient without FVIII inhibitors. An APTT screen, surrogate FVIII and FVIII inhibitor tests were performed on both samples by participating centres. RESULTS: APTT results were below the lower limit of normal range. Chromogenic FVIII assay results with the Hyphen/Biophen human component-based assay gave higher than expected coefficient of variation (CV) results, 38%-40%. The modified one-stage FVIII assay with emicizumab calibrators showed similar results regardless of the APTT reagent. Inhibitor assay median results for sample S18:23 = 1.43 BU (range 0.9-3.0 BU/ml, CV 38%). S18:24 was classified as below the lower limit of detection. CONCLUSION: APTT screens showed a consistent shortening. Unmodified one-stage Factor VIII assay results were remarkably high. APTT-based assays are unsuitable for measurement of coagulation factors or inhibitors in patients treated with emicizumab. Bovine origin chromogenic assays are insensitive to emicizumab and should be used to monitor FVIII levels/FVIII inhibitors in emicizumab treated patients. Product-specific calibrators should be implemented to reduce result variability.