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Tuesday, October 4, 2011

Megaloblastic anaemia: Laboratory diagnosis of megaloblastic anaemia

Laboratory diagnosis of megaloblastic anaemia

A. Routine haematological investigation
                1. Haemoglobin –Decreased. May decrease uptp 3 g/dl. Commonly found at 7-9 g/dl.

                2. MCV-Increased (Macrocytic)

                3. MCH-Increased

                4. MCHC-Normal (normochromic)

                5. Peripheral blood picture:

                                RBC- Many oval macrocytes (Macrovalocytes) are seen which are normochromic or hypochromic with anisocytosis and poikilocytosis.
                                           Howell Jolly bodies may be present
                                           Megaloblasts may be present
                                WBC-Hypersegmented neutrophils are always present (4-9 lobes)
                6. RBC count-Decreased
                7. Haematocrit-Decreased
                8. WBC count-Neutropenia (3000-4000/mm3)
                9. Plateletes/Thrombocytes-mild thrombocytopenia (100,000 to 150,000/mm3)
                10. Reticulocyte count-within 2 %

B. Biochemical findings:

                1. Serum iron and ferritin-increased
                2. Serum lactate dehydrogenase-increased
                3. Serum bilirubin- increased

C. Bone marrow investigations (confirmatory test):

                1. Cellularity: Increased
                2. Myeloid/Erythroid ratio: Decreased
                3. Erythropoiesis: Hyperactive and megaloblastic in nature.
                4. Granulopoiesis: Active. Abnormal large atypical granulocytes are seen usually at the metamyelocyte stage (Giant stab form).
                5. Megakaryopoiesis: Normal or slightly increased.
                6. Bone marrow iron stain: Increased iron granules in erythroid precursors and reticular cells.

D. Special tests to distinguish whether it is due to vitamin B12 or folate deficiency:

                For vitamin B12:
                                                Serum vitamin B12 assay: Radioisotope assay, microbiological assay. In microbiological assay-normal value is 165-1000 ng/l. In deficiency it becomes 100ng/l.
                                Schilling test.
                                Methyl melonic acid excretion in urine.
                                Response to vitamin B12 administration.

                For folate:

                                Serum folate assay: Radioisotope assay, microbiological assay-in deficieny there is less than 3µg/l.
                                Red cell folate assay: Radioisotope assay, microbiological assay.
                                Response to folate administration.

Note : In the making of the above article the follwing books were used:

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