Introduction: In the UK, the fasting plasma concentrations of a panel of gut hormones (vasoactive intestinal peptide (VIP), gastrin, pancreatic polypeptide, glucagon and somatostatin as well as chromogranin A) are frequently measured during the evaluation of patients who have confirmed or clinically suspected neuroendocrine tumours (NETs). However, elevated concentrations of these hormones are sometimes also detected in patients who have no other evidence of a NET. We sought to evaluate the frequency and implications of such abnormal false positive test results in routine clinical practice.
Methods: We conducted a retrospective audit of all fasting gut hormone profile results performed over 12 months at a single large UK hospital that has a large tertiary NET clinical practice.
Results: Fasting gut hormone concentrations were measured in 231 patients during 2017 and 136 of these patients were not already known to have a NET at the time of initial testing. Elevated concentrations of gastrin (75 patients), chromogranin A (35 patients), glucagon (13 patients), somatostatin (5 patients), pancreatic polypeptide (3 patents) and VIP (2 patients) were detected. Of these 31/75 raised gastrin concentrations, 8/35 raised chromogranin A concentrations, 2/13 raised glucagon concentrations, 3/5 raised somatostatin concentrations, 1/3 raised PP concentrations and 1/2 raised VIP concentrations were found in patients who after additional investigations had no other confirmed biochemical or radiological evidence of NET. We extended the audit for glucagon and somatostatin to include the 3 year period Aug 2016Aug 2019 and found a total of 7 false positive raised glucagon concentrations (out of a total of 38 elevated tests) and 4 false positive elevated plasma somatostatin concentrations (out of 9 elevated results).
Conclusions: False positive elevations of plasma gastrin and chromogranin A are relatively common and potential causes such as proton pump inhibitor drug use and atrophic gastritis are well recognised. This study demonstrated that elevated plasma concentrations of other gut hormones are also detected in some patients who have no other evidence of NETs. In such cases a variety of other potential causes (e.g. cirrhosis and medullary thyroid carcinoma for hypersomatostatinaemia and diabetes mellitus, liver or renal impairment for hyperglucagonaemia) should be considered.
02 Dec 2019
UK and Ireland Neuroendocrine Tumour Society