The Schilling test is used to evaluate vitamin B12 absorption in patients with vitamin B12 deficiency. It has multiple stages where radiolabeled vitamin B12 is given orally and/or intravenously along with intrinsic factor. Urine is collected to measure absorption. Abnormal absorption could indicate pernicious anemia from lack of intrinsic factor or other causes of malabsorption. The test helps differentiate these causes of vitamin B12 deficiency.

1. Schilling test
Dr.CSBR.Prasad, M.D.,

2. FIGURE 14-18 Schematic
illustration of vitamin
B12 absorption.
IF, intrinsic factor;
R-binders,
cobalophilins

3. Schilling test
Investigation used for patients with vitamin B12
deficiency
• The purpose of the test is to determine
whether the patient has pernicious anemia
• The Schilling test has multiple stages

4. Stage 1: oral vitamin B12 plus
intramuscular vitamin B12
• Oral dose: patient is given radiolabeled Vit B12
– The most commonly used radiolabels are 57Co and 58Co
• An intramuscular injection of unlabeled vitamin B12 is
given an hour later
• The patient's urine is then collected over the next 24
hours to assess the absorption
• A normal result shows at least 10% of the radiolabeled
vitamin B12 in the urine over the first 24 hours
• In patients with impaired absorption, less than 10% of
the radiolabeled vitamin B12 is detected

7. Stage 2: Vitamin B12 + IF
If an Stage-I is abnormal:
The test is repeated with additional oral intrinsic factor
• If this second urine collection is normal, this shows a lack of
intrinsic factor production, or pernicious anemia.
• A low result on the second test implies “Malabsorption”
– Coeliac disease
– Biliary disease
– Whipple's disease
– Fish tapeworm infestation (Diphyllobothrium latum), or
– Liver disease
– Immerslund syndrome
– Malabsorption of B12 can be caused by intestinal dysfunction
from a low vitamin level in-and-of-itself

8. Stage 3: vitamin B12 and antibiotics
• This stage is useful for identifying patients
with bacterial overgrowth syndrome.

9. Stage 4: vitamin B12 and pancreatic
enzymes
• This stage, in which pancreatic enzymes are
administered, can be useful in identifying
patients with pancreatitis.

10. Combined stage 1 and stage 2
• In some versions of the Schilling's test, B12 can
be given both with and without intrinsic factor
at the same time, using different cobalt
radioisotopes 57Co and 58Co, which have
different radiation signatures, in order to
differentiate the two forms of B12.
• This allows for only a single radioactive urine
collection

12. DDs for
Microcytic Hypochromic Anemia

13. DD for microcytic hypochromicanemia
Diagnosis of Microcytic Anemia
Tests Iron Deficiency Inflammation Thalassemia Sideroblastic
Anemia
Smear Micro/hypo Normal Micro/hypo Variable
micro/hypo with targeting
SI <30 <50 Normal to high Normal to high
TIBC >360 <300 Normal Normal
Percent <10 10–20 30–80 30–80
saturation
Ferritin ( g/L) <15 30–200 50–300 50–300
Hemoglobin Normal Normal Abnormal Normal
pattern
Note: SI, serum iron; TIBC, total iron-binding capacity.

14. Anemia of Chronic Disease

15. Anemia of Chronic Disease
Impaired red cell production associated with
chronic diseases
• Reduction in the proliferation of erythroid
progenitors and
• Impaired iron utilization
It’s due to the production of inflammatory
cytokines

16. Anemia of Chronic Disease
This form of anemia can be grouped into three
categories:
1. Chronic microbial infections
2. Chronic immune disorders
3. Neoplasms

17. Inflammatory cytokines
• TNF
• IL-1
• IL-6
• IF-gamma
• IF-beta

18. Effects of chronic inflammation
• Incresed production of IL-6
• IL-6 stimulate the hepatic production of
hepcidin
• Hepcidin inhibits :
– Ferriportin function in macrophages
– EPO production

19. Regulation of iron absorption

20. Regulation of iron absorption

21. Suppression of erythropoiesis by
inflammatory cytokines

22. Main lab findings
• Low serum iron,
• Reduced total iron-binding capacity, and
• Abundant stored iron in tissue macrophages

23. What might be the reason for iron sequestration
in the setting of inflammation?
• The best guess is that it serves to enhance the
body's ability to fend off certain types of
infection, particularly those caused by
bacteria (such as H. influenzae) that require
iron for pathogenicity
• In this regard it is interesting to consider that
hepcidin is structurally related to defensins, a
family of peptides that have intrinsic
antibacterial activity

24. DD from Iron deficiency anemia
The presence of :
– increased storage iron in marrow macrophages,
– a high serum ferritin level, and
– a reduced total iron-binding capacity
readily rule out iron deficiency as the cause of
anemia.

25. END

26. Dr.CSBR.Prasad, M.D.,
Associate Professor of Pathology,
Sri Devaraj Urs Medical College,
Kolar-563101,
Karnataka,
INDIA.
csbrprasad@reiffmail.com