Direct measurement of acid in gastric contents collected by naso-gastric intubation before (BAO) and after stimulation (MAO) with Histalog or pentagastrin:
  1. Basal acid output (BAO) is determined by measurement of acid in 2-4 15 minute specimens collected before stimulation.
  2. Maximal acid output (MAO) is determined by measurement of acid in 4 30 minute specimens collected after stimulation.
  3. Acid is measured in the specimens by titration with 0.1 N NaOH and expressed in terms of mEq H+/hr. (i.e., in terms of secretion rate rather than in terms of acid content or concentration).
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The Diagnex-Blue Test - provides an indirect indication of adequate gastric acid secretion.

  1. After an overnight fast, and an hour after stimulation with caffein or Histalog, the diagnostic test preparation, a cationic dye (Azure A) bound to cationic exchange resin beads, is administered orally.
  2. Urine specimens, collected for at least two hours, are pooled and the total volume is brought to 300 mls.
  3. Dye concentration of Azure A in the urine specimen is determined spectrophotometrically.
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The Schilling Test

1st Stage

  1. A 1 mg loading dose of vitamin B12 is administered IM to saturate tissue stores.
  2. 50 ug of radioactive cobalt labeled vitamin B12 is administered orally.
  3. The total radioactivity in a 24-48 hour urine collection is determined.

Interpretation of 1st Stage Results:
normal:           8 - 40% of the administered radioactivity is found in the urine collection
vitamin B12 malabsorption: < 8% of the administered radioactivity is found in the urine collection

2nd Stage

If vitamin B12 malabsorption is found, then the test is repeated three days later (second stage), but with the administration of intrinsic factor along with radiolabeled B12.

Interpretation of Second Stage Results
atrophic gastritis with pernicious anemia:           radiolabeled vitamin B12 is absorbed and the content of radiolabeled vitamin B12 in the urine collection becomes normal
intestinal malabsorption:           the content of radiolabeled vitamin B12 in the urine collection remains abnormally low

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The D-Xylose Test:

1. 25 g of D-xylose, dissolved in 250 ml water, is administered orally.

2. A urine specimen is collected for five hours.

3. If renal disease is suspected, a blood specimen is collected after two hours.

Interpretation:

Urine specimen results:
....normal...... ....... > 5g/5 hours
....equivocal... ...... 4-5g/5 hours
....malabsorption... < 4g/5 hours

Blood specimen
....normal ..... ......... > 25 mg/dl
....equivocal... ...... 20-25 mg/dl......
....malabsorption..... < 20 mg/dl

In the absence of renal disease, the result from the urine specimen is more reliable than is the result from the blood specimen.

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Last Updated: Friday, May 23, 1997