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Comparison of sputum induction using inhaled methacholine or hypertonic saline
Alan L James1, Peta S Maxwell, John G Elliot
1West Australian Sleep Disorders Research Institute, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia. ajames@it.net.au
Respirology (Carlton, Vic.)
|February 5, 2005
Summary
Hypertonic saline is more effective for sputum induction than methacholine. However, both methods yield similar inflammatory cell differential counts in respiratory samples.
Area of Science:
- Pulmonary Medicine
- Respiratory Physiology
- Diagnostic Immunology
Background:
- Hypertonic saline is a standard method for inducing sputum to evaluate airway inflammation.
- Methacholine is widely used to assess airway hyperresponsiveness.
Purpose of the Study:
- To compare the efficacy of sputum induction between methacholine and hypertonic saline challenges.
- To analyze the subsequent differential counts of inflammatory cells in induced sputum.
Main Methods:
- Fifty-six subjects underwent randomized, sequential challenges with inhaled hypertonic saline (4.5%) and methacholine (up to 4 micromol).
- Sputum samples were processed, and differential cell counts were determined from May-Grunwald-Giemsa stained cytospins.
Main Results:
- Satisfactory sputum samples were obtained from 29 subjects after hypertonic saline versus 10 after methacholine.
- For subjects with successful induction by both agents, differential cell counts (macrophages, neutrophils, eosinophils, lymphocytes) and squamous cells were comparable.
Conclusions:
- Inhaled methacholine demonstrates a significantly lower yield for sputum induction compared to hypertonic saline.
- Despite differing yields, both challenge agents produce similar sputum differential inflammatory cell profiles.