The Laboratory Monitoring of Altuvoct (Efanesoctocog Alfa): Recommendations From the Laboratory Working Party of the United Kingdom Haemophilia Centres Doctor's Organisation
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Bowyer,Annette Elizabeth
Khan,Mohammed
Lawrence,Caroline
Macdonald,Stephen
Martin,Jill
Platton,Sean
Riddell,Anne
Sanders,Jannene
Williams,Anna
Williams,Stella
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2025
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GENERAL RECOMMENDATIONS: As assays tailored to Altuvoct are necessary, it is essential that every request for a FVIII level for monitoring of Altuvoct clearly identifies when it has been used for treatment of the patient and details the time of sampling relative to timing infusion. RECOMMENDATIONS FOR THE MEASUREMENT OF ALTUVOCT: One-stage assay APTT reagents that are suitable for the post-infusion measurement of Altuvoct are Actin FSL, Synthafax and CK Prest following local verification or validation and when calibrated against a plasma standard (1B). Other one-stage assay APTT reagents that may be suitable for the post-infusion measurement of Altuvoct are APTT-HS, APTT-S, Pathromtin SL and Revohem, but more data with local validation are required (2B). APTT reagents that underestimate the post-infusion measurement of Altuvoct are Synthasil and Thrombocheck SLA. These are not suitable for use (1B). APTT reagents that overestimate the post-infusion measurement of Altuvoct are Actin, Actin FS, Cephen and Cephascreen. These are not suitable for use (1B). CSA are not suitable for the measurement of Altuvoct when calibrated against a plasma calibrator (1B). The use of a correction factor to approximate Altuvoct FVIII activity is not recommended (1B). RECOMMENDATIONS FOR THE MONITORING OF ALTUVOCT IN THE PRESENCE OF FVIII MIMETICS: In the presence of FVIII mimetic therapies, Altuvoct activity should be measured using a chromogenic FVIII assay that uses bovine FX and FIXa substrates (1B). In the presence of FVIII mimetic therapies, one-stage FVIII assays should not be used; Altuvoct activity (measured using a chromogenic FVIII assay that uses bovine FX and FIXa substrates) must be reported with a caveat stating that this is an overestimation of Altuvoct in the order of 1.5-3.0-fold (1B). Chromogenic FVIII assays that use human FX and FIXa substrates should not be used to measure Altuvoct activity in the presence of FVIII mimetics (1B). Chromogenic FVIII assays that use bovine FX and human FIXa substrates require local validation before they can be considered for measuring Altuvoct activity (or residual FVIII in a Bethesda or Nijmegen-modified Bethesda assay) in the presence of FVIII mimetics (1C). RECOMMENDATIONS FOR THE MONITORING OF FVIII INHIBITORS: In the absence of FVIII mimetic therapy, FVIII inhibitors must be assessed using heat-treated patient plasma and a one-stage APTT assay to measure residual FVIII in a Bethesda or Nijmegen-modified Bethesda assay (1B). In the presence of concomitant FVIII-mimetic therapy, FVIII inhibitors must be assessed using heat-treated patient plasma and a chromogenic FVIII assay that uses bovine FX and FIXa substrates to measure residual FVIII in a Bethesda or Nijmegen-modified Bethesda assay (1B).
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Haemophilia : the official journal of the World Federation of Hemophilia