Sputum tests in the diagnosis and monitoring of asthma

Objective: To review the techniques of sputum analysis with relevance to the diagnosis and monitoring of asthma. Data Sources: MEDLINE databases were searched to identify all publications involving sputum studies related to the diagnosis and treatment of asthma from 1990 to October 2003. We also used internal reference files related to sputum and searched bibliographies of relevant articles. The review was limited to human data in English-language publications. Study Selection: Studies were selected by the expert opinions of the authors for quality and relevance to the evaluation of asthmatic inflammation by induced sputum. Results: During the past 10 years, there have been an increasing number of publications concerning the diagnosis and treatment of asthma using sputum analysis. Analysis of induced sputum provides similar data to secretions obtained through bronchial wash, bronchoalveolar lavage, and, to some extent, bronchial biopsy. The techniques of cellular counting and immunochemical analysis are described along with potential problems and pitfalls of these methods. Clinical application of sputum analysis is discussed as it pertains to the diagnosis and monitoring of asthma and asthma-related conditions. Conclusions: Analysis of induced sputum is increasingly being considered as a noninvasive means of evaluating airway inflammation and may provide useful information with regard to the diagnosis and monitoring of asthma in select individuals.