Prediction of infection due to antibiotic-resistant bacteria by select risk factors for health care-associated pneumonia

Background: Pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa now cause pneumonia in patients presenting to the hospital. The concept of health care-associated pneumonia (HCAP) attempts to capture this, but its predictive value is unclear. Methods: We examined patients admitted with pneumonia; infection with a resistant pathogen served as the study end point. Health care-associated pneumonia was present if a patient met one of the following criteria: recent hospitalization, nursing home residence, long-term hemodialysis, or immunosuppression.Wecompared rates of resistant infection among patients meeting any criteria for HCAP with those who did not have HCAP and explored the individual components of the definition. Results: Among the cohort (n=639), resistant pathogens were recovered in 289 (45.2%). Although each component of HCA Poccurred more frequently in persons with resistant infections, the broad definition had a specificity of only 48.6% and misclassified one-third of the subjects. Logistic regression showed 4 variables associated with resistant pneumonia: recent hospitalization, nursing home residence, hemodialysis, and intensive care unit admission. A scoring system assigning 4, 3, 2, and 1 points, respectively, for each variable had moderate predictive power for segregating those with and without resistant bacteria. Among patients with fewer than 3 points, the prevalence of resistant pathogens was less than 20% compared with 55% and more than 75% in persons with scores ranging from 3 to 5 and more than 5 points, respectively (P<.001). Conclusions: Although resistance is common in HCAP, not all component criteria for HCAP convey similar risk. Simple scoring tools may facilitate more accurate identification of persons with pneumonia caused by resistant pathogens.