Page 330 - Concise Pathology for Exam Preparation ( PDFDrive )

12 Haematology 315

• C3b being an opsonin, the cells are phagocytosed by the mononuclear phagocytic system
(haemolysis is extravascular).
• The typical blood picture is of anaemia with reticulocytosis, red cell agglutination and
a positive direct antiglobulin test.

Q. Write briefly on Coombs test.
Ans. Coombs test can be

1. Direct Coombs Test
In this test, patient’s red cells are washed and suspended in saline. Rabbit anti-human
globulin is added. Agglutination of red cells indicates the presence of antibodies on the
surface of red cells.
Indications:
• Haemolytic disease of newborn
• Autoimmune haemolytic anaemia

2. Indirect Coombs Test
• In this test, normal red cells and rabbit anti-human globulin are added to the patient’s
serum. This produces agglutination of red cells if antibodies are present in the serum.
• This detects the incomplete antibodies present in a person’s serum.
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• The serum from the patient is taken and added to a suspension of O RBCs. If the
serum contains incomplete antibodies against Rh antigen, it will coat the O RBCs.
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The suspension is washed many times to remove excess unbound antibodies in the
serum.
• Thereafter, Coombs serum is added. If agglutination occurs, the test is said to be positive.
Indications:
• In crossmatching of blood to detect incomplete antibodies in donor’s serum
• In case of Rh-negative mother, whose first child is Rh-positive, and wants second
conception

Q. Define pancytopenia. Enumerate its causes.
Ans. Pancytopenia is defined as simultaneous presence of anaemia (Hb , 13.5 g/dL),
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leucopenia (TLC, 4 3 10 /L) and thrombocytopenia (150 3 10 /L).
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Causes
• Hypocellular bone marrow: Aplastic anaemia, hypoplastic MDS, cytotoxic drugs and
radiotherapy
• Cellular marrow with systemic disease: Megaloblastic anaemia, hypersplenism,
tuberculosis, Kala-azar, brucellosis, severe infection, alcohol and autoimmune
diseases
• Cellular marrow with primary marrow disease: Bone marrow infiltration as seen in
lymphoma, acute leukaemia, myeloma, carcinoma, paroxysmal nocturnal haemoglobin-
uria, disseminated tuberculosis, myelofibrosis and marrow metastasis

Q. Write briefly on aplastic anaemia.
Ans. Aplastic anaemia is a condition in which bone marrow failure results in pancytopenia
(anaemia, granulocytopenia and thrombocytopenia) in the absence of any abnormal cells in
marrow or blood.

Classification of Aplastic Anaemia
1. Congenital: Fanconi’s anaemia and Schwachman–Diamond syndrome
2. Acquired: Primary or idiopathic (no definite cause) and secondary (definite or likely
agent can be identified)

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