title: Comparison of methods for the analysis of airway macrophage particulate load from induced sputum, a potential biomarker of air pollution exposure.
abstract: BACKGROUND
  Air pollution is associated with a high burden or morbidity and mortality, but exposure cannot be quantified rapidly or cheaply. The particulate burden of macrophages from induced sputum may provide a biomarker. We compare the feasibility of two methods for digital quantification of airway macrophage particulate load.
  
  
  METHODS
  Induced sputum samples were processed and analysed using ImageJ and Image SXM software packages. We compare each package by resources and time required.
  
  
  RESULTS
  13 adequate samples were obtained from 21 patients. Median particulate load was 0.38 μm(2) (ImageJ) and 4.0 % of the total cellular area of macrophages (Image SXM), with no correlation between results obtained using the two methods (correlation coefficient = -0.42, p = 0.256). Image SXM took longer than ImageJ (median 26 vs 54 mins per participant, p = 0.008) and was less accurate based on visual assessment of the output images. ImageJ's method is subjective and requires well-trained staff.
  
  
  CONCLUSIONS
  Induced sputum has limited application as a screening tool due to the resources required. Limitations of both methods compared here were found: the heterogeneity of induced sputum appearances makes automated image analysis challenging. Further work should refine methodologies and assess inter- and intra-observer reliability, if these methods are to be developed for investigating the relationship of particulate and inflammatory response in the macrophage.
authors.affiliation: Liverpool School of Tropical Medicine, Liverpool, UK. hannah.jary@liverpool.ac.uk.
authors.forename: Hannah
authors.initials: H
authors.lastname: Jary
authors.affiliation: Liverpool School of Tropical Medicine, Liverpool, UK. jamie.rylance@liverpool.ac.uk.|Aintree University Hospital, Liverpool, UK. jamie.rylance@liverpool.ac.uk.
authors.forename: Jamie
authors.initials: J
authors.lastname: Rylance
authors.affiliation: Aintree University Hospital, Liverpool, UK. latifa.b.patel@gmail.com.
authors.forename: Latifa
authors.initials: L
authors.lastname: Patel
authors.affiliation: Liverpool School of Tropical Medicine, Liverpool, UK. stephen.gordon@lstmed.ac.uk.|Aintree University Hospital, Liverpool, UK. stephen.gordon@lstmed.ac.uk.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Gordon
authors.affiliation: Liverpool School of Tropical Medicine, Liverpool, UK. kevin.mortimer@lstmed.ac.uk.|Aintree University Hospital, Liverpool, UK. kevin.mortimer@lstmed.ac.uk.
authors.forename: Kevin
authors.initials: K
authors.lastname: Mortimer
mesh_terms: D000328:Adult; D000368:Aged; D000397:Air Pollution; D001249:Asthma / Q000503:physiopathology*; D015415:Biomarkers; D001987:Bronchiectasis / Q000503:physiopathology*; D004781:Environmental Exposure; D005240:Feasibility Studies; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D019570:Inhalation Exposure; D016676:Macrophages, Alveolar / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D052638:Particulate Matter / Q000032:analysis*; D015203:Reproducibility of Results; D012984:Software; D013183:Sputum / Q000166:cytology*; D014797:Vital Capacity
chemical_list: D015415:Biomarkers; D052638:Particulate Matter