Factor VIII and IX assays for post-infusion monitoring in hemophilia patients: Guidelines from the French BIMHO group (GFHT)

Bioclinical features of haemophilia patients in Benin in 2023: Towards better care

OBJECTIVE

To analyse the demographic, clinical and laboratory data of Beninese patients with haemophilia.

METHOD

A prospective survey was conducted in three different hospitals of Benin from April 2021 to March 2022, to analyse clinical and biological features of patients with haemophilia previously diagnosed or identified based on personal/family history.

RESULTS

A total of 101 patients were studied, 97 with haemophilia A and 4 with haemophilia B, including 26 new cases identified after family investigation. Their median age was 11 years, and the most frequent initial manifestations were cutaneous-mucosal haemorrhages (29.70%) and post-circumcision haemorrhages (25.74%). Previous joint bleedings were present in 77% of them, with an arthropathy in 65 cases, which particularly affected the knees (75%), elbows (41%) and ankles (29%). Factor VIII (FVIII) levels combined with activated partial thromboplastin time (APTT) values did not always enable, as would be expected, the distinction between severe and moderate haemophilia, since they were >1 IU/dl in 31 of 74 patients with APTT > 80 s, and between 1 and 2 IU/dl in 26 other cases with previous joint haemorrhages, including 18 with chronic arthropathy. Therefore, for these patients, severe haemophilia could not be excluded, and this uncertainty probably reflects technical difficulties affecting the pre-analytical and analytical stages of the APTT and FVIII/IX assays.

CONCLUSION

Our study proved that haemophilia is a significant reality in Benin, but also remains under-diagnosed in some districts of the country. In addition, more reliable biological tests are needed in the future to better define the severity of the disease and improve treatment of patients.

Evaluating Factor VIII Concentrates Using Clot Waveform Analysis

Background/Objectives: FVIII reagent activity varies across different assays, as well as activated partial thromboplastin time (APTT) reagents. The hemostatic ability of various FVIII reagents was examined via clot waveform analysis (CWA). Methods: APTT was measured using 12 APTT reagents, a small amount of tissue factor-induced FIX activation (sTF/FIXa) and a small amount of thrombin time (sTT) in order to examine 10 FVIII reagents and reference plasma (RP) using CWA. FVIII activity was measured using CWA-APTT, a chromogenic assay, or CWA-sTT. Results: Although the peak time (PT) and peak height (PH) of the CWA-APTT were markedly different in different FVIII reagents using several APTT reagents, the PTs of CWA-APTT were generally normal or shortened and the PHs of CWA-APTT were generally lower than those of RP. The FVIII activity varied, as evaluated using APTT, and was higher when using the CWA-sTT method than the APTT or chromogenic methods. CWA-sTT showed an elevated second peak of first DPH in all FVIII reagents, and both CWA-sTF/FIXa and CWA-sTT were enhanced using APTT reagents. Conclusions: Our evaluation of the hemostatic ability of FVIII reagents varied among APTT reagents. CWA-sTT can be used to further evaluate the hemostatic ability of an FVIII concentrate based on thrombin burst.

The Evaluation of Clot Waveform Analyses for Assessing Hypercoagulability in Patients Treated with Factor VIII Concentrate

BACKGROUND

Regular prophylactic therapy has become an increasingly common treatment for severe hemophilia. Therefore, hypercoagulability-a potential risk factor of thrombosis-is a cause for concern in hemophilic patients treated with a high dose of FVIII concentrate. In clot waveform analysis (CWA)-thrombin time (TT), a small amount of thrombin activates clotting factor VIII (FVIII) instead of fibrinogen, resulting in FVIII measurements using CWA-TT with a small amount of thrombin.

METHODS

The coagulation ability of patients treated with FVIII concentrate or emicizumab was evaluated using activated partial thromboplastin time (APTT), TT and a small amount of tissue factor-induced FIX activation assay (sTF/FIXa) using CWA.

RESULTS

The FVIII activity based on CWA-TT was significantly greater than that based on the CWA-APTT or chromogenic assay. FVIII or FVIII-like activities based on the three assays in plasma without emicizumab were closely correlated; those in plasma with emicizumab based on CWA-TT and chromogenic assays were also closely correlated. CWA-APTT and CWA-TT showed different patterns in patients treated with FVIII concentrates compared to those treated with emicizumab. In particular, CWA-TT in patients treated with FVIII concentrate showed markedly higher peaks in platelet-rich plasma than in platelet-poor plasma. CWA-APTT showed lower coagulability in hemophilic patients treated with FVIII concentrate than in healthy volunteers, whereas CWA-sTF/FIXa did not. In contrast, CWA-TT showed hypercoagulability in hemophilic patients treated with FVIII concentrate.

CONCLUSIONS

CWA-TT can be used to evaluate the thrombin bursts that cause hypercoagulability in patients treated with emicizumab. Although routine APTT evaluations demonstrated low coagulation ability in patients treated with FVIII concentrate, CWA-TT showed hypercoagulability in these patients, suggesting that the evaluation of coagulation ability may be useful when using multiple assays.

Factor VIII and Factor IX Activity Measurements for Hemophilia Diagnosis and Related Treatments

Accurate measurement of clotting factors VIII (FVIII) or IX (FIX) is vital for comprehensive diagnosis and management of patients with hemophilia A or B. The one-stage activated partial thromboplastin time (aPTT)-based clotting assay is the most commonly used method worldwide for testing FVIII or FIX activities. Alternatively, FVIII and FIX chromogenic substrate assays, which assess the activation of factor X, are available in some specialized laboratories. The choice of reagent or methodology can strongly influence the resulting activity. Variation between one-stage FVIII or FIX activities has been reported in the measurement of some standard and extended half-life factor replacement therapies and gene therapy for hemophilia B using different aPTT reagents. Discrepancy between one-stage and chromogenic reagents has been demonstrated in some patients with mild hemophilia A or B, the measurement of some standard and extended half-life factor replacement therapies, and the transgene expression of hemophilia A and B patients who have received gene therapy. Finally, the measurement of bispecific antibody therapy in patients with hemophilia A has highlighted differences between chromogenic assays. It is imperative that hemostasis laboratories evaluate how suitable their routine assays are for the accurate measurement of the various hemophilia treatment therapies.

A French Real-World Evidence Study Evaluating the Efficacy, Safety, and Pharmacokinetic Parameters of rVIII-SingleChain in Patients with Hemophilia A Receiving Prophylaxis

BACKGROUND

 rVIII-SingleChain is a recombinant factor VIII (FVIII) with increased binding affinity to von Willebrand factor compared with other FVIII products. rVIII-SingleChain is indicated for the treatment and prevention of bleeding episodes in patients with hemophilia A.

OBJECTIVES

 To collect real-world evidence data from patients treated with rVIII-SingleChain to confirm the efficacy and safety established in the clinical trial program and carry out a population pharmacokinetic (PK) analysis.

PATIENTS/METHODS

 This interim analysis includes data, collected between January 2018 - September 2021, from patients treated with rVIII-SingleChain prophylaxis at French Hemophilia Treatment centers. Data on annualized bleeding rates, dosing frequency, and consumption before and after switching to rVIII-SingleChain were recorded. A population PK analysis was also conducted to estimate PK parameters.

RESULTS

 Overall, 43 patients switched to prophylaxis with rVIII-SingleChain either from a previous prophylaxis regimen or from on-demand treatment. Following the switch to rVIII-SingleChain, patients maintained excellent bleed control. After switching to rVIII-SingleChain, most patients maintained or reduced their regimen. Interestingly, a majority of patients treated >2 ×/weekly with a standard half-life FVIII reduced both injection frequency and FVIII consumption with rVIII-SingleChain. A PK analysis revealed a lower clearance of rVIII-SingleChain (1.9 vs. 2.1 dL/h) and a longer half-life both in adolescents/adults (n = 28) and pediatric (n = 6) patients (15.5 and 11.9 hours, respectively vs. 14.5 and 10.3 hours) than previously reported.

CONCLUSIONS

 Patients who switched to rVIII-SingleChain prophylaxis demonstrated excellent bleed control and a reduction in infusion frequency. A population PK analysis revealed improved PK parameters compared with those reported in the clinical trial.

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.