Schilling test
With the Schilling test (according to Robert F. Schilling 1953) the absorption of vitamin B 12 in the small intestine can be determined.
execution
The patient is asked to empty the bladder . The 24-hour collection of urine begins at the beginning of the experiment . 1 µg of vitamin B 12 radioactively labeled by 57 Co is administered orally to the patient . The labeled vitamin B 12 is normally absorbed into the blood in the small intestine. One hour after the oral administration of the labeled vitamin, the patient is injected intramuscularly with 1000 μg of unlabelled vitamin B 12 . This displaces the labeled vitamin from the binding proteins, prevents it from being deposited in the liver, and provokes excretion in the urine . Then the amount of radioactive vitamin B 12 present in the collected urine is measured. It is important to stop taking any medication that may impair the absorption of vitamin B 12 . A sufficient distance to other examinations with radioactively marked isotopes must be ensured. Iodinated contrast agents , the radiation of 57 Co decrease.
evaluation
- In a healthy patient, between 10 and 40% of the radioactively labeled vitamin B 12 is excreted.
- In the absence of the intrinsic factor required for the absorption of vitamin B 12 , the proportion of the 57 Co-labeled vitamin B12 excreted in the urine is reduced, since a large part is excreted in the stool. In this case, the test can be repeated after a few days with the addition of intrinsic factor.
- If the functioning of the small intestine is impaired ( malabsorption ), the fraction is also reduced. A retest with intrinsic factor shows no different result.
- An overgrowth of bacteria in the small intestine can also lead to a reduction in the fraction, as various bacteria can also absorb vitamin B 12 .
- Renal insufficiency can delay the elimination of vitamin B 12 .
meaning
The Schilling test is practically obsolete in everyday clinical practice. It was supplanted by the detection of autoantibodies against intrinsic factor and parietal cells , which is easier to carry out and does not require radiation. However, these antibody tests only detect pernicious anemia ; vitamin B12 absorption disorders of other causes are not recorded.
Web links
- Robert Schrempf: Metabolically active, transcobalamin II-bound Vit. B 12 compared to total Vit. B 12 . Dissertation . 2004. (online at: publications.uni-tuebingen.de )
- Repeat test with intrinsic factor on the following day
- Diagnosis of megaloblastic anemia
Individual evidence
- ↑ B. Annibale, E. Lahner, GD Fave: Diagnosis and management of pernicious anemia. In: Current gastroenterology reports. Volume 13, Number 6, December 2011, pp. 518-524, doi : 10.1007 / s11894-011-0225-5 , PMID 21947876 (review).
