Schillings test

Schillings test

• This test is used to evaluate the absorption of vitamin B12 in the GIT

• Test is performed in two parts

  • Part I –

    • 0.5 to 1μg of radiolabeled vitamin B12 is administered orally

    • After 2 hours 1000μg of unlabeled vitamin B12 is given as an intramuscular dose

    • This intramuscul;ar dose of vitamin B12 saturates the vit B12 binding sites of transcobalamin I and II and displaces any bound radiolabeled vitamin B 12

    • This causes the urinary excretion  of absorbed radiolabeled vitamin B12

    • Radioactivity is measured as in subsequently collected 24hour urine sample and is expressed as percentage of ttotal oral dose

    • In normal individuals, more than 7% of the oral dose of vitamin B12 is excreted in urine

    • If excretion is less than 7%, it indicates impaired absorption which may be due to either malabsorption or lack of intrinsic factor

    • If the part I result is abnormal then part II test is conducted

  • Part II

    • patient is given radiolabeled vitamin B12 along with intrinsic factor orally

    • After 2 hours 1000μg of unlabeled vitamin B12 is given as an intramuscular dose

    • If excretion becomes normal, then the cause is lack of intrinsic factor

    • If excretion is below normal, it indicates malabsorption in small intestine

• Interpretation of Schillings test

  • Part I normal – Dietary deiciency

  • Part I abnormal, Part II normal – Pernicious anemia and gastrectomy

  • Part I abnormal, Part II abnormal – Malabsorption in small intestine

• Disadvantages of test

  • This test is time taking and complicated

  • Procuring radiolabeled vitamin B12 is difficult

  • Collection of urine and renal functions also affect the test results

Reference

• Shirish M Kawthalkar. Essentials of Hematology. First edition, 2006