The Evolution of Sputum Cytometry to Assess Bronchitis

Canadian Respiratory Journal, Jul 2018

Hui Fang Lim, Parameswaran Nair

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The Evolution of Sputum Cytometry to Assess Bronchitis

Can Respir J evolution of sputum cytometry to assess bronchitis Hui Fang Lim MBBS MMed MRCPUK 0 2 Parameswaran Nair FRCPC 1 2 0 Division of Respiratory & Critical Care Medicine, National University Hospital , Singapore 1 Firestone Institute for Respiratory Health , St Joseph's 2 Healthcare & McMaster University , Hamilton, Ontario irway inflammation is not routinely assessed in the management of airway diseases such as asthma, chronic obstructive pulmonary disease or chronic cough. This is an important limitation because the pathogenesis of airway disease includes three nonoverlapping components: airway inflammation (ie, bronchitis); airflow obstruction; and hyper-responsiveness (1). Bronchitis can be measured noninvasively by sputum cell counts, the fraction of exhaled nitric oxide (FENO) and exhaled breath measurements (2). Sputum cell count quantification has been shown to have important clinical use in reducing eosinophilic asthma exacerbations (3,4), guiding treatment and selecting patients for treatment with biologics (5). Athough exhaled nitric oxide can predict steroid responsiveness in patients with mild airway diseases (6), it may have less clinical applicability, particularly in patients with severe airway diseases because it may not be directly related to the degree of sputum eosinophilia (7) and, thus, may not be able to monitor disease and titrate treatment (8). Sputum cell counts can help advance our understanding of different endophenotypes and their pathobiological pathways in conditions such as asthma and chronic obstructive lung disease (9,10). Compared with FENO, sputum cell counts provide information on the type (eosinophilic versus neutrophilic) and degree of airway inflammation. This will increase our understanding of various endophenotypes - especially the severe and treatment-refractory types - to help physicians predict response to novel therapies and, importantly, to allocate the appropriate treatment to the correct patient. - A applicable in western Canada and at elevated altitude. Appropriate statistical methods were used, although the sample size was not justified and the lower sample size compared with previous studies may have contributed to the slightly higher variability in cell counts observed in this study. A ?normal? reference range may vary according to demographic factors, comorbidities and exposure to environmental influences such as pollution and smoking. The study by Belda et al ( 16 ) reported a higher total and absolute neutrophil cell count compared with the other studies. It was conducted in Hamilton (Ontario) and may have been skewed by the ambient pollution of an industrialized city and by prevailing climatic conditions that may affect the neutrophil and macrophage counts ( 20 ). They also reported increased sputum eosinophilia with atopy and female sex. The study by Thomas et al ( 18 ) found that the sputum neutrophil differential counts increased significantly with age. Yet, it is reassuring that the central measures and variances reported from these centres from three different continents are remarkably similar. Currently, there are several limitations in the routine sputum processing methods in practice: first, sputum specimens must be examined within 2 h; second, as described above, it requires multiple steps; and third, it requires a certified technologist trained in the examination of cell counts for it to be standardized, reliable and real time. Refrigeration at 4?C can preserve cell morphology and accuracy of cell counts for up to 9 h ( 21 ). Sputum fixation or preservation of sputum may extend the time between collection and processing by allowing sputum examination to be delayed for up to 72 h ( 22,23 ), thus facilitating transport to a dedicated laboratory for subsequent examination. Sputum can be preserved in 10% buffered formalin or 2% paraformaldehydedithiothreitol fixative. The preservatives may increase cellular counts by rapidly inactivating cellular enzymes and by stabilizing cell membranes, thus resulting in increased cell recovery. However, the effect of preservation on total expectorate compared with saliva-free expectorate may be different and this may affect the interobserver repeatability of cell differentials ( 24 ). Thus, it is important to note that the normal reference range using the preservation methods described in the article by Davidson et al ( 19 ) may be slightly different from the methods that examine freshly expectorated sputum; however, the differences may not be clinically relevant. This method may help to promote widespread use of sputum analysis in clinical practice and research, and remove one barrier from its implementation in the routine care of patients with airway diseases. In the future, development of a point-ofcare biomarker for bronchitis would further enhance its widespread adoption and clinical application ( 25 ). Dr Nair is supported by a Canada Research Chair in Discloure: 1 Rosi E, Ronchi MC, Grazzini M, et al. Sputum analysis, bronchial hyperresponsiveness, and airway function in asthma: Results of a factor analysis. J Allergy Clin Immunol 1999;103:232-7. 2 Nair P, Hargreave FE. Measuring bronchitis in airway diseases: Clinical implementation and application: Airway hyperresponsiveness in asthma: Its measurement and clinical significance. Chest 2010;138:38S-43S. Lim and Nair MEDIATORS INFLAMMATION The Scientiifc World Journal Hindawi Publishing Corporation ht p:/ www.hindawi.com Hindawi Publishing Corporation ht p:/ www.hindawi.com Journal of Diabetes Research Disease Markers Journal of Hindawi Publishing Corporation ht p:/ www.hindawi.com Immunology Research PPAR Research Hindawi Publishing Corporation ht p:/ www.hindawi.com Submit your manuscr ipts http://www.hindawi.com Obesity Journal of Ophthalmology Hindawi Publishing Corporation ht p:/ www.hindawi.com Stem Cells International Hindawi Publishing Corporation ht p:/ www.hindawi.com Evidence-Based Complementary Alternative Medicine and Journal of Oncology Disease nal and Mathematical Methods Hindawi Publishing Corporation ht p:/ www.hindawi.com AIDS and 3. Jayaram L , Pizzichini MM , Cook RJ , et al. 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Hui Fang Lim, Parameswaran Nair. The Evolution of Sputum Cytometry to Assess Bronchitis, Canadian Respiratory Journal, DOI: 10.1155/2013/927384