Page 83 - Essential Haematology

Chapter 5 Macrocytic anaemias / 69

serum folate tends to rise but the red cell folate falls. Treatment
In the absence of B 12 defi ciency, however, the red
Most cases only need therapy with the appropriate
cell folate is a more accurate guide of tissue folate
vitamin (Table 5.9 ). If large doses of folic acid (e.g.
status than the serum folate. Measurement of serum
5 mg/day) are given in B 12 defi ciency they cause a
methylmalonic acid is a test for B 12 defi ciency and
haematological response but may aggravate the neu-
of homocysteine for folate or B 12 defi ciency. Th ese
ropathy. They should therefore not be given alone

are not specific, however, and it is diffi cult to estab-

unless B 12 deficiency has been excluded. In severely

lish normal levels in different age groups. Th ese tests

anaemic patients who need treatment urgently it
are not widely available.
may be safer to initiate treatment with both vita-
Tests for c ause of v itamin B 12 or

f olate d efi ciency

For B 12 deficiency, absorption tests using an oral Table 5.8 Tests for cause of vitamin B 12 or

dose of radioactive labelled cyanocobalamin were folate defi ciency.
valuable in distinguishing malabsorption from an
inadequate diet but are not now available. Vitamin B 12 Folate
Useful tests are listed in Table 5.8 . Th ese are
Diet history Diet history
mainly concerned with assessing gastric function and
testing for antibodies to gastric antigens. In all cases Serum gastrin Tests for intestinal
of pernicious anaemia endoscopy studies should malabsorption

be performed to confirm the presence of gastric IF, parietal cell Anti - transglutaminase and
atrophy and exclude carcinoma of the stomach. antibodies endomysial antibodies

For folate deficiency, the dietary history is most
Endoscopy Duodenal biopsy

important, although it is difficult to estimate folate
Underlying disease
intake accurately. Unsuspected gluten - induced
enteropathy or other underlying conditions should
IF, intrinsic factor.
also be considered (Table 5.5 ).
Table 5.9 Treatment of megaloblastic anaemia.

Vitamin B 12 defi ciency Folate defi ciency
Compound Hydroxocobalamin Folic acid
Route Intramuscular * Oral

Dose 1000 μ g 5 mg

Initial dose 6 × 1000 μ g over 2 – 3 weeks Daily for 4 months

Maintenance 1000 μ g every 3 months Depends on underlying disease; life - long therapy may

be needed in chronic inherited haemolytic anaemias,
myelofi brosis, renal dialysis
Prophylactic Total gastrectomy Pregnancy, severe haemolytic anaemias, dialysis,
Ileal resection prematurity
* Some authors have recommended daily oral or sublingual therapy of vitamin B 12 defi ciency.