Introduction: Erythrocyte morphology changes not only by primary hematological diseases but also by systemic inflammation, ineffective erythropoiesis and nutritional deficiencies. Red blood cell distribution width (RDW) is a parameter reflecting erythrocyte morphology. We aimed to investigate the relationship of RDW with chronic obstructive pulmonary disease (COPD) stages, BODE index in COPD patients.

Methods: Medical records of 200 COPD patients between december 2017 and 2022 were studied retrospectively. Demographic features, BODE index factors and oxygen saturation were recorded. A complete blood count (CBC) was performed, RDW values was measured in stable condition.

Results:The mean age was 64.01±12.01 years with a sex ratio of 8.09. Distribution of the COPD groups of the patients were Gold A (8%), Gold B (13.5%), Gold C (24%) and Gold D (54.5%). High RDW was significantly associated with severe disease stages (p<0.05). The severity of the disease according to the BODE index was distributed as follows: 19.5% of patients had an index [0 to 2], 13% had an index [3 to 4] 16.5% had an index [5 to 6 ] and 9% had an index >7 with an average BODE index of 3.96. The RDW rate was significantly associated with the BODE index, as the BODE index increased RDW also increased (p=0.001).

Conclusion: The variability in the size of circulating erythrocytes increases as the COPD severity progresses. Therefore, a simple and noninvasive test, such as RDW, might be used as a biomarker in the evaluation of the severity of COPD