RDWCV

RDW-CV stands for red cell distribution width – coefficient of variation. It is a parameter reported in a standard complete blood count that describes the variation in red blood cell size (volume) within a blood sample. RDW-CV complements other red cell indices, particularly mean corpuscular volume (MCV), by quantifying the degree of anisocytosis, or uneven cell sizes, among circulating red cells.

RDW-CV is typically expressed as a percentage. It is calculated from the red cell distribution width standard deviation (RDW-SD) and the MCV using the relationship RDW-CV = (RDW-SD / MCV) × 100, with RDW-SD given in femtoliters and MCV in femtoliters. Automated hematology analyzers perform this calculation as part of the CBC.

Reference ranges for RDW-CV can vary by laboratory and population, but a common adult reference range is roughly 11.5% to 14.5%. Values may differ in newborns and across different analyzer platforms.

Clinical interpretation of RDW-CV is nonspecific and must be considered with other CBC indices. An increased RDW-CV indicates greater heterogeneity in red cell sizes (anisocytosis) and can be seen in iron deficiency anemia, mixed nutritional deficiencies, megaloblastic anemia, hemolytic conditions, inflammatory states, or after transfusion. A normal RDW-CV with microcytosis may suggest a thalassemia trait, whereas a high RDW-CV with microcytosis often points toward iron deficiency or mixed etiologies. In macrocytic anemia, RDW-CV is frequently elevated due to variable cell sizes.

Measurement is performed by automated hematology analyzers; factors such as sample quality, instrument calibration, and reference ranges can affect values. RDW-CV is informative when interpreted in the context of the full CBC and clinical picture.