Encyclopedia of Medical Immunology

2014 Edition
| Editors: Ian R. Mackay, Noel R. Rose, Dennis K. Ledford, Richard F. Lockey

Testing: Sputum Eosinophil Count

  • Daniel A. Searing
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-9194-1_508


Airway inflammation; Sputum cell count


Sputum is a respiratory expectorant composed primarily of mucus and does not contain nasopharyngeal secretions or saliva. The sputum eosinophil count refers to the number of eosinophils in sputum, typically expressed as a percentage of the total cell count. Examination of sputum is a noninvasive way to assess for airway inflammation.

Collection and Processing

Sputum can be naturally produced via a productive cough or induced by inhaling bronchial irritants. Protocols for induced sputum typically involve 3 % hypertonic saline administered via nebulizer (AARC 1993; Pavord et al. 1997; National Jewish Health 2010). Oftentimes, patients are pretreated with a bronchodilator. The sample may then be treated with dithiothreitol (DTT), a mucolytic agent, to promote cell dispersion. The sample is centrifuged and subsequently undergoes Wright staining. The differential cell count is then obtained using bright field microscopy.


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© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Division of Allergy and Clinical Immunology, Department of PediatricsNational Jewish Health University of ColoradoDenverUSA