Hematology / CBC
Reticulocyte countRetic
Young red cells; the bone marrow's response to anemia.
Sample
EDTA whole blood
Clinical reference range
25 to 100 ×10⁹/L
Adult absolute
Conv: 25–100 ×10⁹/LFunc: 50–100 ×10⁹/L
Biology
What it measures
Reticulocytes are anucleate RBCs that retain RNA for 1–2 days post-marrow release. The reticulocyte production index (RPI) corrects for Hct and shift cells.
Clinical use
Why we order it
Distinguish hypoproliferative anemia (low retic) from blood loss/hemolysis (high retic) and monitor treatment response.
Lens · Clinical
Interpretation by lens
Clinical interpretation
RPI >2 in anemia → hemolysis or blood loss; RPI <2 → marrow underproduction.
Differential
Causes of abnormal values
Causes of HIGH
- ↑Hemolysis
- ↑Acute blood loss (~3–5 days later)
- ↑Response to iron/B12/folate replacement
- ↑EPO therapy
Causes of LOW
- ↓Iron, B12, or folate deficiency before treatment
- ↓Anemia of chronic disease
- ↓Aplastic anemia
- ↓Chronic kidney disease (low EPO)
Pitfalls
Pre-analytic & interpretation traps
- !Always interpret reticulocytes in relation to Hct (use absolute count or RPI, not raw %).
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