What is Schilling test?
It is a test to determine the cause of vitamine B12 defeciency. It is done by the measurement of urinary excretion of radio-isotope labeled oral vitamine B12 with and without the administration of intrinsic factor of Castle.
The capacity of the body to absorb vitamin B12 is measured by administration of a dose of vitamine B12 labeled by radio isotope of cobalt and measuring the percentage that is excreted in the urine.
58Cobalt and 57Cobalt are the radioisotopes used normally.
1. 1µg of radiolabeled vitamin B12 is given orally to a fasting patient.
2. 2 hours later 1000 µg of unlabeled vitamin B12 is given intramuscularly.
3. The imtramuscular injection flushes out about 1/3 of the absorbed radioactive vitamin B12 into the urine with the next 24 hours.
4. The result is seen:
In normal patient, 10% or more of the radiolabeled 1 µg dose is excreted in the urine.
In pernicious anaemia, patients excrete <5% uptp 7% of the dose.
In atrophic gastritis, borderline result of upto 10% maybe seen.
5. If result is subnormal (below 10%) , a further dose of radioactive vitamin B12 is given orally with intrinsic factor of Castle.
6. If result returns to normal, then the diagnosis is pernicious anaemia.
Note : In the making of the above article the follwing books were used: