In direct ELISAs, approximately 15% cross-reactivity with recombinant human (rh) FGF R4 is observed, 5% cross-reactivity with rhFGF R1 alpha (IIIb), rhFGF R1 alpha (IIIc), and rhFGF R1 beta (IIIb) is observed, and less than 1% cross-reactivity with recom