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Chapter 162 Resources for the Hematologist e3

Reticulocyte Count (Absolute and Percentage)
Summary points • Used to assess erythroid production
• In setting of anemia, can aid in distinguishing between destructive process (hemolysis) and marrow production
problem
Methodology Automated hematology analyzer, flow cytometry
Specimen requirements Whole blood: EDTA
Indications Differential diagnosis of anemia (destruction versus marrow production problem); evaluate marrow response to anemia;
monitor response to therapy (treatment of nutritional anemias, post immunosuppressive therapy for aplastic anemia,
post growth factor therapy, post chemotherapy, or bone marrow transplant)
Reference range Table 162.3
Interpretation • Elevated with marrow response to anemia, implying decreased RBC life span (hemolysis), marrow recovery (post
injury, chemotherapy, or bone marrow transplant), or response to treatment (immunosuppressive therapy in aplastic
anemia, nutritional replacement in iron, B 12 , or folate deficiency)
• Decreased (or inadequately elevated) in nutritional anemias, marrow suppression (infections, toxic exposures,
malignancy), marrow failure
• Corrected reticulocyte count (absolute reticulocyte count/reticulocyte maturation time) and RPI [reticulocyte percentage
× (hematocrit/45) × (1/reticulocyte maturation time)] adjust for the degree of anemia and account for reticulocyte
maturation time in assessing appropriateness of the marrow response
Absolute count more meaningful than percentage in some settings (aplastic anemia)
Related tests Complete blood count, reticulocyte hemoglobin, immature reticulocyte fraction, mean reticulocyte volume, corrected
reticulocyte count, RPI, direct antiglobulin test, markers of hemolysis
Interfering substances Clotted or hemolyzed sample
EDTA, Ethylenediaminetetraacetic acid; RBC, red blood cell; RPI, reticulocyte production index.

Immature Reticulocyte Fraction
Summary points • Indicator of marrow response to anemia
• May be useful to follow engraftment after bone marrow transplant
Methodology Automated hematology analyzer—flow cytometric method
Specimen requirements Whole blood: EDTA
Indications Suspected anemia, differential diagnosis of anemia, assess marrow response to anemia, after marrow injury,
chemotherapy, growth factor treatment, or bone marrow transplant
Reference range Table 162.4
Interpretation • Decreased in marrow failure or suppression states, increased with marrow response to anemia
• Increased levels after bone marrow transplant appear to correlate with engraftment and precede other cell counts
Related tests Complete blood count, reticulocyte count, reticulocyte hemoglobin, mean corpuscular volume reticulocyte
Interfering substances Clotted or hemolyzed sample
Reference Piva E, Brugnara C, Chiandetti L, et al: Automated reticulocyte counting: State of the art and clinical applications in the
evaluation of erythropoiesis. Clin Chem Lab Med 48:1369, 2010.
EDTA, Ethylenediaminetetraacetic acid.

Reticulocyte Hemoglobin Equivalent (Ret-He)
Summary points • May be useful in early detection of iron deficiency
• CHr is a similar but not identical parameter; whether Ret-He or CHr is reported depends on the hematology
analyzer used
Can be used to monitor response to therapy
Methodology Automated hematology analyzer—flow cytometric method
Specimen requirements Whole blood: EDTA
Indications Suspected anemia, assessment of iron status, differential diagnosis of anemia, assess response to growth factor
therapy
Reference range Table 162.5
Interpretation • Decreased in iron deficiency and may be decreased in thalassemia
• Decreased levels in renal failure may suggest functional iron deficiency
Related tests Complete blood count, reticulocyte count, immature reticulocyte fraction, mean corpuscular volume reticulocyte,
iron studies
Interfering substances Hemolyzed or clotted specimen
References Brugnara C, Mohandas N: Red cell indices in classification and treatment of anemias: from M.M. Wintrobe’s
original 1934 classification to the third millennium. Curr Opin Hematol 20:222, 2013.
Piva E, Brugnara C, Chiandetti L, et al: Automated reticulocyte counting: State of the art and clinical applications in
the evaluation of erythropoiesis, Clin Chem Lab Med 48:1369, 2010.

CHr, Reticulocyte hemoglobin content; EDTA, ethylenediaminetetraacetic acid; Ret-He, reticulocyte hemoglobin equivalent.