red blood cell distribution width-coefficient of variation CMO:0000041 EFO:0005192 EFO:0009188 RDW RDW-CV Red cell distribution width The red cell distribution width (RDW) is a measurement derived from the red blood cell distribution curves generated on automated hematology analyzers and is an indicator of variation in RBC size within a blood sample. The RDW is used along with the indices (MCV, MCH, MCHC) to describe a population of RBCs. The RDW measures the deviation of the RBC width, not the actual width or size of individual cells. The RDW-CV is a calculation based on both the width of the distribution curve and the mean cell size. It is calculated by dividing the standard deviation of the mean cell size by the MCV of the red cells and multiplying by 100 to convert to a percentage. VT:0000248 clinical_measurement_ontology red blood cell distribution width red blood cell morphological measurement