Hemolytic anemia laboratory findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Hemolytic anemia is anemia caused secondary to shortened survival of circulating red blood cells. The normal life span of RBCs is 110 to 120 days. RBC destruction before that time is defined as hemolytic anemia. As opposed to the normal senecence of RBC, the random hemolysis (premature RBC death) is increased in hemolytic anemia.

Laboratory Findings

Peripheral blood smear

• Fragments of the red blood cells ("schistocytes") can be present.
• Some red blood cells may appear smaller and rounder than usual (spherocytes).
• Reticulocytes are present in elevated numbers. This may be overlooked if a special stain is not used
• The reticulocytes response act as an important indicator for the severity of the hemolytic anemia. The different methods used to judge the correct response are, absolute reticulocyte count, corrected reticulocyte count, and reticulocyte production index.

Absolute reticulocyte count

The normal values are:

• RBC count - 5 million/microLitre
• Reticulocyte count - 0.5 -1.5 %
• Absolute reticulocyte count - 25,000 to 75,000/microLitre

Corrected reticulocyte count

The corrected absolute reticulocyte count = absolute reticulocyte count / reticulocyte maturation time (in days).

Reticulocyte production index

It corrects the reticulocyte response through two mechanism:

• The degree of anemia (done by normalizing hematocrit of 45%)
• Reticulocyte maturation time (RMT)
• The Reticulocyte maturation time is 1.0 days for a hematocrit of 45 % to 2.5 days for a hematocrit of 15 %:
• Reticulocyte production index = Reticulocytes % x (HCT / 45) x (1 / RMT)
  • Normal value of RPI is 1.
  • RPI is said to be increased if it is more than 2
  • Value low than 1 shows hypoproliferative responses

Other lab tests

• Elevated lactate dehydrogenase (LDH)
• Elevated haptoglobin
• The direct Coombs test is positive if hemolysis is caused by an immune process

Liver function test

• The level of unconjugated bilirubin in the blood is elevated. This may lead to jaundice.

Urinalysis

• Hemosiderin in the urine indicates chronic intravascular hemolysis.
• There is also urobilinogen in the urine.

(Images shown below are courtesy of Melih Aktan MD, Istanbul Medical Faculty - Turkey, and Hospital Universitario La Fe Servicio Hematologia)

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  Microangiopathic hemolytic anemia
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  Microangiopathic hemolytic anemia