SCHILLING'S TEST

INDICATIONS:

1. Evaluation of patients with low serum Vitamin B12 levels.
2. Diagnosis of pernicious anemia.
3. Evaluation of small intestinal malabsorption.

PATIENT PREPARATION:

1. The patient must fast overnight and remain fasting for at least 2 hours after ingesting the radiopharmaceutical.
2. The patient should not receive parenteral B-12 for at least 3 days before the test.
3. Patient should not be taking Reglan, a cathartic or other GI stimulants.
4. Recent nuclear study with Technetium-99m will interfere with counting and give false results.

RADIOPHARMACEUTICAL:

Vitamin B12 labeled with Co-57 is used; 0.5 mCi is given orally in capsule form. An IM injection of non-radioactive B12 is given 20 minutes after the oral dose. The critical organ is the liver (0.1-0.2 rad).

SCANNING TIME:

A small urine sample is collected before the examination to use as background. Patient is then instructed to collect a 24 hr urine sample. The importance of obtaining a complete sample cannot be overemphasized. For inpatients, please give instructions to the nursing staff in this regard.

OTHER CONSIDERATIONS:

1. The test is performed first without, then with, intrinsic factor (if B12 absorption is low).
2. Contraindications for giving Co-57 are pregnancy and breast feeding.

RATIONALE:

Non-radioactive vitamin B12 saturates receptor sites so that any oral radioactive B12 absorbed is excreted in the urine. This is counted and compared to a standard to evaluate percent absorbed. Low absorption (< 8%) strongly suggests GI malabsorption. Low absorption that is corrected by administering intrinsic factor is diagnostic of pernicious anemia.