Sputum eosinophilia negates need to perform sputum Gram's stain

A total of 1878 sputum specimens were evaluated to assess the potential of encountering a sputum Gram's stain with clinically useful positive data in the presence of sputum eosinophilia. Wet preparations were used to assess the adequacy of the specimen and to quantitate eosinophils. Quantitative sputum Gram's stains were performed. When more than 50% of the cells observed on sputum wet preparation were eosinophils, there were no positive Gram's stains. When more than 20% of the cells were eosinophils, there was a 1% prevalence of potentially clinically useful positive Gram's stains. The data strongly suggest that sputum eosinophilia obviates the need to perform a sputum Gram's stain since it is extremely unlikely that it would be useful in diagnosing a bacterial infection of the lower respiratory tract.