UTILITY OF GRAM STAIN IN EVALUATION OF SPUTA FROM PATIENTS WITH CYSTIC-FIBROSIS

The utility of sputum Gram stain in assessing salivary contamination a nd in predicting the presence of pathogens on the basis of morphology was investigated in 287 respiratory specimens from patients with cysti c fibrosis. Where acceptability for culture was defined as a leukocyte /squamous epithelial cell ratio of >5, 76.6% (220 of 287) of respirato ry specimens received in the laboratory were considered acceptable. Un acceptable specimens were more common in younger patients. The positiv e predictive value of the Gram stain for growth from acceptable sputum samples was 98% for Pseudomonas aeruginosa, 84.4% for Pseudomonas cep acia, 86.3% for Staphylococcus aureus, and 100% for Haemophilus influe nzae. In cystic fibrosis patients, as has been reported for respirator y specimens in general, Gram stain of respiratory specimens is helpful for interpreting culture results.