Total acidity of gastric juice is higher than free acidity because total acidity also includes:

Combined acid and weak organic acids

Bicarbonate from the stomach wall

Gastric function tests

14 Kerala PSC Lab Technician Gr II practice questions on Gastric function tests, part of Biochemistry. The first 14 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
Total acidity of gastric juice is higher than free acidity because total acidity also includes:
1. ACombined acid and weak organic acids
2. BFree hydrochloric acid only
3. CPepsin activity in the sample
4. DBicarbonate from the stomach wall
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Answer: A · Combined acid and weak organic acids
Free acidity is the unbound hydrochloric acid, titrated with 0.1 N NaOH to the Töpfer's reagent end point (about pH 3.5). Total acidity is titrated further, to the phenolphthalein end point (about pH 8.3). It includes the free HCl plus acid bound to protein (combined acid) and weak acids such as lactic acid and acid phosphates. The difference between the two titrations is the combined acidity.
- B: Free hydrochloric acid alone is the free acidity.
- C: Pepsin is an enzyme and is not counted as acidity.
- D: Bicarbonate neutralizes acid and would lower acidity.
Question 2 · Medium
In tubeless gastric analysis with azure A resin (Diagnex Blue), the presence of free acid in the stomach is shown by:
1. AA fall in blood pH
2. BBlue dye excreted in the urine
3. CBlue dye passed in the stool
4. DA rise in serum gastrin
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Answer: B · Blue dye excreted in the urine
The swallowed resin carries azure A dye bound to an exchange resin. Hydrogen ions of free gastric acid displace the dye, which is absorbed from the intestine and excreted in the urine, where it is estimated by color. Little or no dye in the urine suggests achlorhydria. The test is only a screen, because kidney or liver disease, poor absorption and incomplete urine collection affect it.
- A: Gastric acid secretion does not lower blood pH; it causes an alkaline tide.
- C: Dye that stays bound to the resin passes in the stool and shows no acid.
- D: Serum gastrin is a separate test and is not part of the resin method.
Question 3 · Hard
In a patient with a suspected duodenal ulcer, a 10 mL sample of gastric juice needs 3.5 mL of 0.1 N NaOH to reach the Töpfer end point. Its free acidity is:
1. A350 mEq/L
2. B3.5 mEq/L
3. C35 mEq/L
4. D0.35 mEq/L
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Answer: C · 35 mEq/L
The NaOH used is 3.5 mL × 0.1 mEq/mL = 0.35 mEq, which neutralized the free acid in 10 mL of juice. Per litre this is 0.35 × 1,000 ÷ 10 = 35 mEq/L. The same number is the result in clinical units, the mL of 0.1 N NaOH needed for 100 mL of juice. Each wrong answer comes from leaving out one of these steps.
- A: 350 leaves out the 0.1 normality of the NaOH.
- B: 3.5 does not scale the 10 mL sample up to 100 mL or a litre.
- D: 0.35 is the mEq in the 10 mL sample, not per litre.
Question 4 · Easy
Which tube is commonly used to aspirate gastric juice for a fractional test meal?
1. ARyle's tube
2. BSengstaken-Blakemore tube
3. CMiller-Abbott tube
4. DFoley catheter
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Answer: A · Ryle's tube
Ryle's tube is a thin nasogastric tube with a weighted tip and side holes, passed through the nose or mouth into the stomach after an overnight fast. The resting juice is aspirated first, and samples are then drawn at intervals after the test meal or stimulant. The weighted tip helps the tube reach the most dependent part of the stomach, where the juice collects.
- B: The Sengstaken-Blakemore tube compresses bleeding esophageal varices.
- C: The Miller-Abbott tube is a balloon-tipped intestinal tube.
- D: A Foley catheter drains the urinary bladder.
Question 5 · Easy
In gastric analysis, pentagastrin is injected to measure the:
1. AIntrinsic factor output
2. BBasal acid output
3. CGastric emptying time
4. DMaximal acid output
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Answer: D · Maximal acid output
Pentagastrin is a synthetic peptide containing the active end of gastrin, and a dose of 6 µg/kg stimulates the parietal cells to their maximum. Gastric juice is collected in 15-minute samples for an hour, and the acid in them gives the maximal acid output. The basal acid output is measured from the juice collected in the hour before stimulation. No acid after pentagastrin (achlorhydria) is seen in pernicious anemia.
- A: Intrinsic factor is not measured in the pentagastrin test.
- B: Basal acid output is measured before any stimulant is given.
- C: Gastric emptying is studied by imaging, not by acid output.
Question 6 · Easy
Gastric aspirate that looks like coffee grounds contains:
1. ABile regurgitated from the duodenum
2. BUndigested food residue
3. CBlood altered by gastric acid
4. DExcess mucus from gastritis
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Question 7 · Medium
A 58-year-old man with pernicious anemia undergoes gastric analysis. The expected result is:
1. ANormal acid output with raised pepsin
2. BFree acid appearing only after pentagastrin
3. CVery high basal acid output
4. DNo free acid even after pentagastrin
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Question 8 · Medium
A 65-year-old man with weight loss has no free HCl in his gastric juice, and the Uffelmann test for lactic acid is positive. This suggests:
1. ACarcinoma of the stomach
2. BZollinger-Ellison syndrome
3. CDuodenal ulcer
4. DBenign gastric ulcer
Answer and explanation in LearnFree account
Question 9 · Easy
In gastric analysis, which indicator marks the end point when total acidity is titrated with 0.1 N NaOH?
1. APhenolphthalein
2. BCongo red
3. CMethyl orange
4. DTöpfer's reagent
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Question 10 · Hard
A man with dyspepsia gives four 15-minute basal gastric samples: 25 mL with acidity 40 mmol/L; 20 mL, 45 mmol/L; 18 mL, 50 mmol/L; 16 mL, 50 mmol/L. What is his basal acid output (BAO)?
1. A0.9 mmol/h
2. B14.4 mmol/h
3. C3.6 mmol/h
4. D36 mmol/h
Answer and explanation in LearnFree account
Question 11 · Medium
In gastric juice titration, Töpfer's reagent is used to measure free HCl because it:
1. AChanges colour near pH 3
2. BChanges colour near pH 8.5
3. CBinds combined acid
4. DPrecipitates the pepsin
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Question 12 · Easy
Which gastric cells secrete both hydrochloric acid and intrinsic factor?
1. AChief cells
2. BG cells
3. CParietal cells
4. DMucous neck cells
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Question 13 · Medium
After a vagotomy, a rise in gastric acid output during insulin-induced hypoglycemia indicates:
1. AIncomplete vagotomy
2. BPernicious anemia
3. CZollinger-Ellison syndrome
4. DSuccessful vagotomy
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Question 14 · Hard
A 45-year-old man has recurrent peptic ulcers in the jejunum and chronic diarrhea. His basal acid output is 20 mmol/h and the maximal acid output after pentagastrin is 28 mmol/h. The most likely diagnosis is:
1. ASimple duodenal ulcer
2. BGastric carcinoma
3. CAtrophic gastritis
4. DZollinger-Ellison syndrome
Answer and explanation in LearnFree account

Gastric function tests

Total acidity of gastric juice is higher than free acidity because total acidity also includes:

In tubeless gastric analysis with azure A resin (Diagnex Blue), the presence of free acid in the stomach is shown by:

In a patient with a suspected duodenal ulcer, a 10 mL sample of gastric juice needs 3.5 mL of 0.1 N NaOH to reach the Töpfer end point. Its free acidity is:

Which tube is commonly used to aspirate gastric juice for a fractional test meal?

In gastric analysis, pentagastrin is injected to measure the:

Gastric aspirate that looks like coffee grounds contains:

A 58-year-old man with pernicious anemia undergoes gastric analysis. The expected result is:

A 65-year-old man with weight loss has no free HCl in his gastric juice, and the Uffelmann test for lactic acid is positive. This suggests:

In gastric analysis, which indicator marks the end point when total acidity is titrated with 0.1 N NaOH?

A man with dyspepsia gives four 15-minute basal gastric samples: 25 mL with acidity 40 mmol/L; 20 mL, 45 mmol/L; 18 mL, 50 mmol/L; 16 mL, 50 mmol/L. What is his basal acid output (BAO)?

In gastric juice titration, Töpfer's reagent is used to measure free HCl because it:

Which gastric cells secrete both hydrochloric acid and intrinsic factor?

After a vagotomy, a rise in gastric acid output during insulin-induced hypoglycemia indicates:

A 45-year-old man has recurrent peptic ulcers in the jejunum and chronic diarrhea. His basal acid output is 20 mmol/h and the maximal acid output after pentagastrin is 28 mmol/h. The most likely diagnosis is: