Blood Neutrophils Could Be a Biomarker for Pneumonia Risk in COPD

Patients with chronic obstructive pulmonary disease (COPD) have a higher risk of pneumonia and often have worse outcomes in terms of pneumonia severity. Additionally, while inhaled corticosteroid (ICS) therapy helps to reduce COPD exacerbations, ICS has been linked with an increased pneumonia risk in COPD. No definitive biomarkers for pneumonia risk have been established for patients with COPD, but a recent study explored whether blood neutrophils could have predictive value.

The paper, published in Respiratory Research, explains that while neutrophils have been identified as an effector cell in the pathogenesis of COPD, there is little known about how much the increase in circulating neutrophils in COPD is driven by the inflammatory process rather than a response to infection. The researchers hypothesized that an association might exist between blood neutrophil levels and pneumonia risk, and they conducted a post hoc analysis of patient data from 10 clinical trials from the GlaxoSmithKline clinical trial registry to evaluate such a potential association.

Among the 10 studies, conducted among 11,131 patients between 1998 and 2011, there were 6735 patients who received ICS therapies and 4396 who received non-ICS therapies, and the 2 cohorts were well matched in their neutrophil counts and demographics.

The researchers found that patients with lower neutrophil counts had similar reductions in pneumonia, regardless of whether their treatment contained or did not contain ICS. Across the studies, a lower proportion of patients below the median neutrophil count experienced pneumonia versus those at or above the median (2.8% vs 3.9%; hazard ratio, 0.75; 95% CI, 0.61-0.92).

In the studies that were conducted up to week 52 or week 104, patients with the highest baseline neutrophil quartile had an increased risk of pneumonia when compared with the lower 3 quartiles at week 52. In studies that were conducted up to week 24, pneumonia was risk was higher at week 24 in patients whose baseline neutrophil counts were at or above the median versus those whose counts were below the median.

“Taken together, these results suggest that blood neutrophils could potentially be a useful biomarker for informing physicians if a patient has a high risk of pneumonia, when considering ICS therapy,” wrote the authors.

Additional research will be needed to further assess the relationship between neutrophils and pneumonia risk, however, as the study did not provide information on the nature of the association between neutrophils and risk, and “only further studies of the airway microbiome, infection risk and neutrophil counts are likely to elucidate the nature of this relationship.”

Reference

Pascoe SJ, Papi A, Midwinter D, Lettis S, Barnes N. Circulating neutrophils levels are a predictor of pneumonia risk in chronic obstructive pulmonary disease. Respir Res. 2019;20(1):195. doi: 10.1186/s12931-019-1157-0.