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. Author manuscript; available in PMC: 2018 Apr 11.
Published in final edited form as: Int J Endocr Oncol. 2017 Oct 11;4(4):167–185. doi: 10.2217/ije-2017-0018

Table 1.

Currently recommended approach and criteria for the biochemical diagnosis of ZES

  1. When ZES is suspected, the initial test recommended is a fasting serum gastrin (FSG) determination in the absence of antisecretory therapy (Sensitivity- 98–100% in ZES patients various series [42]).

    [Today the FSG determination is frequently performed when ZES is first suspected and in many cases patients are taking antisecretory therapy. If the FSG is not elevated, it should be repeated, and if it remains normal, ZES is essentially excluded (>97%) except for uncommon exceptions (1). However, even if the FSG is elevated, ZES cannot be diagnosed without confirmation of concomitant inappropriate secretion of gastric acid and exclusion of other rare conditions (e.g., retained antrum syndrome)].

  2. An elevated FSG can only be accurately interpreted together with a measure of gastric secretory capacity (usually a gastric pH) to confirm the presence of inappropriate hypergastrinemia. This generally requires delaying or stopping gastric antisecretory therapy, which is a potentially dangerous maneuver particularly if the patient is taking PPI’s and not performed under appropriate conditions.

  3. If the FSG is increased >10-fold [generally >1000 pg/ml, with normal <100 pg/ml] and the gastric pH is ≤2, then ZES is present [retained gastric antrum syndrome [173] can usually be excluded by history] (The combination of FSG>10 fold increased and gastric pH≤2 is present in 32% of ZES patients [42, 174].

  4. If the FSG is increased, <10-fold [generally <1000 pg/ml with normal <100 pg/ml] and the gastric pH is ≤2, additional testing is recommended (either a secretin test or a basal acid output (BAO)). [Some have used sensitive imaging modalities (such as 68Ga-DOTATATE PET/CT positivity as an alternative approach instead] (2)

  5. A secretin test(performed off PPIs) demonstrating an increase in serum gastrin of >120 pg/ml has a sensitivity of 94% and specificity of 100% for ZES [77] (3). A BAO>15 mEq/hr (no previous gastric surgery; >5 mEq/hr after previous gastric acid reducing surgery) with the FSG/pH changes listed in IV above, establishes the diagnosis of ZES [10, 17, 42].

(1)

ZES patients post incomplete gastrinoma resection [51], MEN1/ZES patients post effective parathyroidectomy (usually 3.5–4 gland resection) for hyperparathyroidism [52], and uncommonly other ZES patients (0–2%) [42] can have a normal FSG.

(2)

The role of imaging for diagnosis of ZES has not been systematically studied and is not clearly defined at present.

(3)

Achlorhydria is a well-recognized cause of false-positive secretin testing [79, 116]