The Schilling Test
1st Stage
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.
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 |
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 hoursBlood 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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