RESULTS: Seventeen pairs of sputum cultures were identified. Included subjects had a mean age of 30 (range 21-65), 58.8% of subjects were female. 11/17 culture pairs had discordant pathogens. As expected, CF culture isolated more pathogens including additional Pseudomonas isolates (10/17 pairs). In 3/17 pairs, the standard sputum culture isolated pathogens not found on the CF culture. When comparing results of antibiotic sensitivities in cultures that isolated Pseudomonas (9 pairs of cultures), 7/9 of cultures sets disclosed discordant susceptibilities. 59% of the regular cultures either identified an additional pathogen or gave a different antibiotic sensitivity as compared to CF culture.