Area under the inhibitory curve and a pneumonia scoring system for predicting outcomes of vancomycin therapy for respiratory infections by Staphylococcus aureus

Treatment factors predictive of clinical and microbiological outcomes and t he relationship between a pneumonia scoring system and clinical outcomes in vancomycin-treated patients with a Staphylococcus aureus-associated lower respiratory-tract infection (LRTI) were studied. A computer database review identified patients for whom S. aureus was isola ted from a respiratory-tract specimen between January 1 and December 31, 19 98, and who had antimicrobials ordered within 72 hours of isolation of that organism. Through further review of individual patient charts, this group was restricted to those treated with vancomycin for a documented S. aureus- associated LRTI. Classification-and-regression-tree (CART) modeling was per formed to determine which clinical variables were correlated with clinical outcomes and microbiological outcomes. Median changes in clinical pneumonia scores from baseline in two patient groups (those with clinical success an d those with clinical failure) were compared. Seventy patients met the study criteria. CART modeling found that both outc omes were associated with area under the inhibitory curve (AUIC). The pneum onia scoring system was predictive of eventual clinical success as early as day 3 of treatment; having at least a 4-point decrease in the pneumonia sc ore by day 3 was correlated with an 87% clinical success rate. Both AUIC and a pneumonia scoring system were useful for predicting clinica l and microbiological outcomes of vancomycin therapy in patients with LRTIs caused by S. aureus.