Would polycythemia vera cause a low rdw?

Not that I know of.: The big changes of this are elevated rbc count, hemoglobin, hematocrit, and decreased ESR (erythrocyte sedimentation rate). The elevations come without decrease in volume, and can be up to 70-80% for hematocrit, and 8-9 million rbc count. Changes in RDW may be from so many rbc's in the system, but even if they do occur, do not apparently have effect on prognosis or relevance to the cause of this.