Here are the results of our July, 2018 Quick Question, "How do you measure factor IX therapy?"
- Clot-based factor assay (34) 83%
- Immunoassay (4) 10%
- Chromogenic substrate (3) 7%
We had 41 respondents. Although there are a few chromogenic substrate-based factor IX assays available worldwide, none has been approved by the US FDA , though two are marketed in the US for "research use only." Conversely, there are a number of chromogenic factor VIII assays available, some of which are approved. In general, chromogenic substrate methodology provides for greater precision, and in the case of synthetic extended half-life therapeutic factor concentates, greater accuracy. Chromogenic substrate approaches are likely grow in popularity as these concentrates replace standard preparations.