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Investigations And Etiological Diagnosis To Detect The Presence Of Hemolysis In Anemia
Investigations To Detect Hemolysis In Anemia
Detecting Serum Heptaglobins
Proper laboratory investigations are necessary to establish the diagnosis of hemolytic anemia. The direct method is to measure the red cell lifespan, but this may not be available in many laboratories in developing countries. The presence of hemolysis can be inferred by demonstrating the following
- Rise in serum bilirubin
- Reduction of serum haptoglobin, and
- Increase in serum lactic dehydrogenase
Tests to detect the presence of hemolysis
Reticulocytosis: Reticulocytes are demonstrated by staining with vital stains like brilliant cresyl blue. Increase in reticulocyte count above 1.5% suggests increased erythropoiesis.
Hemolytic anemia must be suspected wherever the reticulocyte count is above 5% and this is not accountable by other causes like recent blood loss or hematinic therapy. Rarely, reticulocytosis may be absent even in hemolytic states when there are antibodies against red cell precursors.
Bilirubin: Presence of unconjugated hyperbilirubinemia (above 1 mg/dl) in the absence of primary hepatic disease strongly suggests hemolysis. The metabolic products of bilirubin like urobilinogen in the urin and stercobilinogen in feces are also increased.
Serum haptoglobins: These are alpha 2-glycoproteins which are normally present in serum at a concentration of 50-150 mg/dl. They combine with hemoglobin liberated from red cells to form complexes which are rapidly destroyed. Consequently, haptoglobin level in serum is lowered in active hemolysis.
Serum lactic dehydrogenase level: This is invariably elevated above the normal range (70240 IU/ml) in hemolytic anemia. This is more marked in intravascular hemolysis.
Bone marrow: The bone marrow shows erythroid hyperplasia in the vast majority of cases. Megaloblastosis occurs when there is associated folate deficiency.
Isotopic Method: Red cell survival and the sites of hemolysis can be studied isotopically using 51Cr. The severity of hemolysis can also be established by this method.
Intravascular Hemolysis Detection
History and physical examination helps in revealing the cause in most of the cases. Examination of the peripheral blood film, tests for intravascular hemolysis and the demonstration of antibodies serve to identify the underlying factors.
Examination of a properly made blood film gives the most valuable clues to the etiology in most of the cases. Large number of spherocytes are suggestive of hereditary spherocytosis or immune hemolytic anemias. Gross alteration of red cell morphology and the presence of basophilic stippling, hypochromia and target cells favour the diagnosis of thalassemia and hemoglobinopathies. Schistocytes, which are fragmented erythrocytes, are seen characteristically in microangiopathy and mechanical causes for hemolysis. Stomatocytosis is seen in hereditary stomatocytosis and hepatic disorders. Acanthocytes are seen in abetalipoproteinemia and in chronic liver diseases. In Nigeria for instance, no examination of blood film is complete without careful search for malarial parasites which may be the cause of hemolysis in a significant proportion of cases.
Anisopoikilocytosis, polychromasia, punctuate basophilia, and Cabot’s rings are suggestive of active erythropoiesis and also dyserythropoiesis which may indirectly indicate hemolysis. In hemolysis, due to drug toxicity, Heinz bodies can be demonstrated by suitable techniques.
Intravascular hemolysis: In this condition, free hemoglobin in the serum rises to 100-200 mg per cent or even more whereas the normal level is only 2-5 mg/dl.
Demonstration of antibodies by Coomb’s test: The direct Coomb;s test is a screening test for the detection of antibodies present on the erythrocytes. It is usually positive in immunohemolytic anemias. The indirect Coomb’s test detects antibodies present in the serum.
Other special tests
Various other special tests are employed for the diagnosis of hemolytic anemias;
- Osmotic fragility is increased and autohemolysis is present in spherocytosis
- Sucrose-hemolysis test and Ham’s acid serum test are positive in paroxysmal nocturnal hemoglobinuria
- Detection of abnormal hemoglobins, assays for erythrocyte enzymes, demonstration of Heinz bodies and immunological studies are all employed in specific cases.
© 2014 Funom Theophilus Makama