title: Discontinuation of proton pump inhibitors during assessment of chromogranin A levels in patients with neuroendocrine tumours.
abstract: BACKGROUND
  The aim of this prospective study was to examine whether discontinuation of proton pump inhibitors (PPIs) or replacement by H(2)-receptor antagonists (H2RA) resulted in a decrease of chromogranin A (CgA) levels in 196 patients with well-differentiated neuroendocrine tumours (NETs).
  
  
  METHODS
  Patients with an unexpectedly high CgA level not connected with NET disease discontinued PPIs, or used H2RA instead; 2 weeks later CgA level was measured again.
  
  
  RESULTS
  In all, 19 out of 196 (10%) patients showed unexpected elevated CgA levels, they all used PPI. In 11 out of 19 patients with no evidence of the disease, median CgA decreased from 390 μg l(-1) during PPI treatment to 56 μg l(-1) after discontinuation (P=0.003). In 8 out of 19 patients with stable disease, median CgA decreased from 618 to 318 μg l(-1) (P=0.012). In 12 out of 19 patients who ceased all acid inhibition, CgA levels decreased by 82%, while in the seven patients who replaced PPI by H2RA, CgA decreased by 77% (P=0.967).
  
  
  CONCLUSIONS
  Proton pump inhibitor use causes falsely elevated CgA levels in patients with NET. We recommend to stop, or replace PPI by H2RA, to obtain a reliable CgA value.
authors: Department of Clinical Chemistry, The Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital, PO Box 90203, 1006 BE Amsterdam, The Netherlands. t.korse@nki.nl
authors: C M
authors: CM
authors: Korse
authors: M
authors: M
authors: Muller
authors: B G
authors: BG
authors: Taal
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D053379:Chromogranin A / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000378:metabolism*; D054328:Proton Pump Inhibitors / Q000008:administration & dosage*; D055815:Young Adult
chemical_list: D053379:Chromogranin A; D054328:Proton Pump Inhibitors