I would like to know if taking a PPI (Nexium) will alter the chromogranin A count?

Our Medical Director, Richard R.P. Warner MD, states that ALL PPI’s (example, Nexium) will alter CgA results and
should therefore be withheld for about  1 month prior to  the chromogranin A (CgA) test.  Zantac or Tagamet can be substituted during this period.