Detection of NF-kB (p65) in the serum is interesting and not surprising. Numerous proteins are are detected in serum. Therefore, additional information could help- is the serum from a healthy individual? If not, any known inflammatory diseases? The presence of p65 in the serum could indicate cell death-associated with pyroptosis in cells and tissues, which is accompanied by inflammation.
Clearly interesting to measure; just to remember that NFkB is a complex, and maybe would be more informative to detect other proteins along with p65, and try to correlate with specific pathologies.