Use of severity scoring and stratification factors in clinical trials of hospital-acquired and ventilator-associated pneumonia.

Clinical studies of hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) enroll patients with a very wide spectrum of disease, in part, related to the patient and/or host, the causative pathogen, and the severity of the pulmonary disease, severity of illness, and other comorbidities. Studies have identified the presence of some baseline variables (eg, Acute Physiologic Assessment and Chronic Health Evaluation II score <or= 20 or absence of comorbidities) as independent predictors of survival. Incorporation of severity scoring and risk adjustment in clinical trials of HAP and VAP may be a significant advancement because it has been noted that all-cause mortality varies widely on the basis of a number of these factors. In this article, we review the use of severity scoring and risk stratification factors, including time of onset, severity of disease, scoring systems, underlying disease and comorbidities, and effects of prior antibiotic therapy (including impact on treatment effect) in clinical trials of HAP and/or VAP.