Ans. B: Reduced BAO : MAO ratio Zollinger-Ellison syndrome (ZES) is a rare condition characterized by peptic ulcers that are refractory to conventional medical therapy. Gastrin-producing tumors or gastrinomas cause excessive gastric acid secretion, leading to ulcers of the upper GI tract, as well as diarrhea and severe abdominal pain. Laboratory studies to confirm the diagnosis of ZES include the following: Measurements of fasting serum gastrin levels - Gastrin levels higher than 100 pg,/mL are highly suggestive of ZES. If the gastric pH level is less than 2.5, a gastrin level of higher than 1000 pg/mL is diagnostic of ZES. If the patient is not receiving acid-suppressing medication and the gastric pH levels are higher than 2, ZES can be ruled out. Secretin stimulation test After blood to measure the basal gastrin level is obtained, 2 IU/kg of secretin is intravenously administered. Blood is obtained at 2.5 minutes, 5 minutes, 10 minutes, 15 minutes, and 30 minutes. An increase of serum gastrin levels to higher than 200 pg/mL is diagnostic of ZES. - It is the most impoant diagnostic test to exclude other conditions with increased acid secretion, hypergastrinemia, or both. - Clinical conditions in which patients present with hypergastrinemia, such as gastric outlet obstruction, pernicious anemia, renal failure, and achlorhydria due to atrophic gastritis, must be excluded with secretin provocative testing. Measurement of basal acid output - Before measurement of the basal acid output (BAO), acid-inhibitory agents must be discontinued: 24 hours for H2 receptor antagonists and 7 days for proton pump inhibitors (PPIs). - In the 24 hours prior to the test, the patient receives antacids. - In an unoperated stomach, a BAO of more than 15 mEq/h is diagnostic of Zollinger-Ellison syndrome. If the patient underwent gastric resection for acid reduction, a BAO of more than 10 mEq/h is diagnostic for Zollinger-Ellison syndrome. If the patient has multiple endocrine neoplasia type 1 (MEN-1), other laboratory abnormalities may be suggestive of Zollinger-Ellison syndrome. - High plasma calcium levels High parathyroid hormone (PTH) levels - High prolactin levels