3. Schilling test
Investigation used for patients with vitamin B12
deficiency
โข The purpose of the test is to determine
whether the patient has pernicious anemia
โข The Schilling test has multiple stages
4. Stage 1: oral vitamin B12 plus
intramuscular vitamin B12
โข Oral dose: patient is given radiolabeled Vit B12
โ The most commonly used radiolabels are 57Co and 58Co
โข An intramuscular injection of unlabeled vitamin B12 is
given an hour later
โข The patient's urine is then collected over the next 24
hours to assess the absorption
โข A normal result shows at least 10% of the radiolabeled
vitamin B12 in the urine over the first 24 hours
โข In patients with impaired absorption, less than 10% of
the radiolabeled vitamin B12 is detected
5.
6.
7. Stage 2: Vitamin B12 + IF
If an Stage-I is abnormal:
The test is repeated with additional oral intrinsic factor
โข If this second urine collection is normal, this shows a lack of
intrinsic factor production, or pernicious anemia.
โข A low result on the second test implies โMalabsorptionโ
โ Coeliac disease
โ Biliary disease
โ Whipple's disease
โ Fish tapeworm infestation (Diphyllobothrium latum), or
โ Liver disease
โ Immerslund syndrome
โ 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
โข This stage is useful for identifying patients
with bacterial overgrowth syndrome.
9. Stage 4: vitamin B12 and pancreatic
enzymes
โข This stage, in which pancreatic enzymes are
administered, can be useful in identifying
patients with pancreatitis.
10. Combined stage 1 and stage 2
โข 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.
โข This allows for only a single radioactive urine
collection
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 10โ20 30โ80 30โ80
saturation
Ferritin ( g/L) <15 30โ200 50โ300 50โ300
Hemoglobin Normal Normal Abnormal Normal
pattern
Note: SI, serum iron; TIBC, total iron-binding capacity.
15. Anemia of Chronic Disease
Impaired red cell production associated with
chronic diseases
โข Reduction in the proliferation of erythroid
progenitors and
โข Impaired iron utilization
Itโs 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
18. Effects of chronic inflammation
โข Incresed production of IL-6
โข IL-6 stimulate the hepatic production of
hepcidin
โข Hepcidin inhibits :
โ Ferriportin function in macrophages
โ EPO production
22. Main lab findings
โข Low serum iron,
โข Reduced total iron-binding capacity, and
โข Abundant stored iron in tissue macrophages
23. What might be the reason for iron sequestration
in the setting of inflammation?
โข 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
โข 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 :
โ increased storage iron in marrow macrophages,
โ a high serum ferritin level, and
โ a reduced total iron-binding capacity
readily rule out iron deficiency as the cause of
anemia.