Pulmonary hypertension, or high blood pressure in the blood vessels that supply the lungs, is a major complication of COPD. This respiratory disease is characterized by chronic inflammation of the lungs — particularly in the airways sacs where gas exchanges occur — that damages lung tissue and impairs respiratory function.
Studies have suggested that measures of red blood cell distribution width (RDW) — a measure of variability in the volume of erythrocytes, or red blood cells, in circulation — can be a useful predictor of clinical outcomes in people with cardiovascular and respiratory diseases, from heart failure to COPD.
Higher RDW measures could result from problems in red blood cell production, or excessive loss of these cells either through cell destruction or unusually short lifespans, the researchers said.
They investigated whether RDW might be a marker of COPD patients’ likelihood of developing pulmonary hypertension. To find out, the researchers evaluated RDW values in 252 people with COPD, including 39 with secondary PH. These patients had a mean age of 70.95, and a majority in both groups were male.
People with COPD and PH were found to have a nearly 10% higher RDW compared with those without this secondary disease, 15.10 versus 13.70 (normal volume ranges are 11.5% to 14.5%), the study said. Levels of brain natriuretic peptide (BNP), suggestive of damage to cardiac tissue, also were five times higher in those with both diseases.
Further analysis confirmed that RDW values were an independent prognostic factor of PH risk in COPD patients, with high RDW values linked to a 1.5-fold higher risk. The optimal cutoff value of RDW for predicting PH was 14.65, with a sensitivity of 69.2% and a specificity of 82.8%.
Analysis of BNP levels and pulmonary artery-to-ascending aorta ratio (PA:A) — two common measures of disease outcomes for PH secondary to COPD — mirrored the results obtained with RDW analysis. In general, high BNP values (above 146.105) predicted secondary PH with a sensitivity of 82.1% and specificity of 86.8%, while PA:A ratio of 0.925 had a 79.5% sensitivity and 82.8% specificity.
“Accumulating data have revealed that elevated RDW level is associated with increased mortality in stable COPD patients,” the researchers said. They added that their work supports RDW values as a useful and “cost-effective alternative” in predicting “the outcome of COPD patients with PH.”
Overall, “RDW is significantly increased in COPD patients with PH and thus may be a useful biomarker for PH secondary to COPD,” the team concluded.