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RDW-indicator of red blood cell heterogeneity

RDW (Red Cell Distribution Width) – an indicator of the heterogeneity of red blood cells

RDW reflects the degree of difference in the size of red blood cells (anisocytosis). The higher the RDW, the greater the spread in red blood cell volumes. This parameter helps to diagnose anemia and other hematopoietic disorders.

RDW rate in a blood test

  • Adults and children: 11.5-14.5%
  • Newborns: 14.9-18.7% (temporary increase due to physiological immaturity of hematopoiesis)

The role of RDW in the body

Red blood cells normally have approximately the same size (80-100 pl). RDW shows:

  • The norm (11.5-14.5%) is a homogeneous population of red blood cells.
  • Increased RDW (>14.5%) – a significant size spread (micro-and macrocytes are present simultaneously).
  • Reduced RDW (<11.5%) – all red blood cells are almost identical (rarely of clinical significance).

Deviations from the norm: causes and symptoms

1. Increased RDW (anisocytosis)

Main reasons:

  • Iron deficiency anemia (most common) – the bone marrow produces small (microcytes) and normal red blood cells.
  • Vitamin B₁₂ or folic acid deficiency -large macrocytes appear on the background of normal cells.
  • Hemolytic anemia – when red blood cells are destroyed, young cells of different sizes enter the blood.
  • Chronic liver/kidney diseases – hemoglobin synthesis and red blood cell maturation are disrupted.
  • Oncology (leukemia, myelodysplasia) – pathological hematopoiesis.

Symptoms depend on the type of anemia.:

  • Weakness, pallor, shortness of breath.
  • Jaundice (with hemolysis).
  • Glossitis, numbness of the extremities (with B₁₂ deficiency).

2. Reduced RDW

It is rare and usually not associated with pathologies. Possible reasons:

  • Normal variant in healthy people.
  • Macrocytic anemia at an early stage (all red blood cells are evenly enlarged).

Symptoms:
Usually absent, but with anemia possible:

  • Fatigue, dizziness.

Diagnostic value of RDW

Combination of IndicesPossible Diagnosis
RDW ↑ + MCV ↓Iron Deficiency Anemia, Thalassemia
RDW ↑ + MCV ↑Vitamin B₁₂/Folate Deficiency Anemia, Liver Disease
RDW ↑ + MCV NormalEarly Stage of Anemia, Hemolysis
RDW Normal + MCV ↓Chronic Diseases, Thalassemia

Treatment

Depends on the reason for changing the RDW:

  • Iron Deficiency – Iron supplements + vitamin C.
  • B₁₂/folate deficiency -b₁₂ injections, folic acid tablets.
  • Hemolysis – elimination of the cause (for example, treatment of autoimmune diseases).

Important: RDW is an early marker of anemia. It can increase even before the hemoglobin decreases, which helps to start treatment at the initial stage.

Practical example:

A patient with RDW of 16% and MCV of 72 pl is likely to have iron deficiency. with low ferritin and blood iron levels.