Article Text

Download PDFPDF

Sputum colour can identify patients with neutrophilic inflammation in asthma
  1. Kavita Pabreja1,
  2. Peter Gibson1,
  3. Alyssa J Lochrin2,
  4. Lisa Wood2,
  5. Katherine J Baines2 and
  6. Jodie L Simpson2
  1. 1Priority Research Centre for Healthy Lungs, School of Medicine and Public Health, Hunter Medical Research Institute, The University of Newcastle, Newcastle, New South Wales, Australia
  2. 2Priority Research Centre for Healthy Lungs, School of Biomedical Sciences and Pharmacy, Hunter Medical Research Institute, The University of Newcastle, Newcastle, New South Wales, Australia
  1. Correspondence to Professor Jodie L Simpson; jodie.simpson{at}newcastle.edu.au

Abstract

Introduction Sputum colour is associated with neutrophilic inflammation in chronic bronchitis and chronic obstructive pulmonary disease (COPD). Neutrophilia and sputum expectoration is notable in asthma, but whether sputum colour is associated with and predicts the presence of neutrophilic inflammation in asthma is unknown. The objective of the study is to assess the ability of sputum colour in distinguishing asthma inflammatory phenotypes.

Methods Induced sputum samples collected from 271 adults with stable asthma were retrospectively assessed. Sputum colour was determined using the BronkoTest sputum colour chart and correlated to differential cell counts and CXCL-8 concentration. Neutrophilic inflammation was defined as an age-corrected sputum neutrophil proportion (≥61.6% for age 20–40 years; ≥63.2% for age 40–60 and ≥67.2% for age >60 years), whereas neutrophilic bronchitis (NB) was defined as high total cell count (≥5.1×106 cells/mL) plus an increased age-corrected neutrophil proportion. The optimal cut-off for sputum colour to predict neutrophilic inflammation and NB was determined using receiver operator characteristic curve analysis.

Results A sputum colour score of ≥3 represented and predicted neutrophilic inflammation with modest accuracy (area under the curve (AUC)=0.64; p<0.001, specificity=78.4%, sensitivity=49.2%). Participants with a sputum colour score of ≥3 had significantly (p<0.05) higher CXCL-8, total cells and neutrophil number and proportion. Sputum colour score was also positively correlated with these factors. Sputum colour score ≥3 predicted NB with reasonably good accuracy (AUC=0.79, p<0.001, specificity=79.3%, sensitivity=70.7%).

Conclusions Visual gradation of sputum colour in asthma relates to high total cell count and neutrophilic inflammation. Assessment of sputum colour can identify adults with asthma who are likely to have NB without the need for sputum processing and differential cell count, which may facilitate asthma management.

  • asthma
  • inflammation
  • neutrophils
  • neutrophilic bronchitis
  • neutrophilic inflammation
  • sputum
  • sputum colour

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

View Full Text

Statistics from Altmetric.com

Footnotes

  • Contributors PG and JLS: study conception/design. PG, AJL, LGW, KJB and JLS: data acquisition. KP, AJL and JLS: data analysis/interpretation. KP, PG and JLS: manuscript drafting. KP, PG, AJL, LGW, KJB and JLS: critical manuscript revision. KP, PG, AJL, LG, KJB and JLS: final manuscript approval.

  • Funding The grant support was offered by National Health and Medical Research Council (NHMRC), Australia.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Ethics approval The Hunter Area Health Service and University of Newcastle Research Ethics Committees.

  • Provenance and peer review Not commissioned; externally peer reviewed.

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.