Community-acquired pneumonia affects millions of people and results in 1.2 million hospital admissions in the United States each year . In Canada, pneumonia accounts for 1 million physician visits and is a major leading cause of death with ~8,000 deaths per year, most of which occur in the elderly population . An estimated $40 billion is expended annually on pneumonia in the US, including both direct and indirect costs . Over half of patients with community acquired pneumonia (CAP) are treated as outpatients  with 10 % subsequently hospitalized . Understanding the prognosis for outpatients with CAP is crucial for optimizing their care . Yet, few studies have evaluated outcomes in CAP outpatients with the majority focusing on short-term mortality and site-of-care decisions. For example, the PORT study investigators evaluated 944 highly selected outpatients and reported a 30-day mortality rate of 0.6 % . More recently, several smaller studies (range of 906 to 1881 patients) have estimated 30-day mortality rates ranging from 0.1 % to 2.5 % [7–10], although a recent large administrative claims study suggest 30-day mortality rates over 4 % among elderly patients . Similarly, few studies have assessed short-term morbidity (e.g., return to Emergency Departments, hospitalization) in CAP outpatients. In the studies conducted to date, admission to hospital following Emergency Department discharge for CAP is between 1.5-8.5 % within 30-days [6, 8, 10, 12, 13]. In the only previous study to examine Emergency Department return visits, 3 % of outpatients returned within 30 days .
To date, we believe that inadequate information is available for front-line clinicians managing CAP outpatients. Unlike patients admitted to hospital with CAP, little research has been completed on outpatients. In the few studies conducted to date, none have adequately evaluated prognostic factors associated with improved survival or adverse events in CAP outpatients . Thus, numerous inadequacies exist in the extant literature and much of clinical practice in this area has been extrapolated from studies of inpatients. We believe that a large population based cohort of CAP outpatients is urgently needed to begin studying this important but under-researched condition . Therefore, we have assembled such a cohort. In this report, we describe the rationale, key objectives, design and assembly, and characteristics of more than 3000 outpatients with pneumonia.
The key research objectives include, but are not limited to:
Understanding the short and long-term health outcomes for patients with CAP managed in an outpatient setting. Outcomes will include mortality, hospitalizations, ambulatory care visits, and physician visits related to recurrent pneumonia and from all-causes.
Verifying the utility of various prognostic factors and risk scores commonly used for inpatients with pneumonia and examining them in the outpatient setting.
Identifying novel independent prognostic factors associated with significant short and long-term adverse outcomes in CAP outpatients including the impact of comorbidities (e.g. mental health, cardiovascular) and treatment options (e.g., antibiotics) on recovery from an episode of CAP in the community.
Describing risk-adjusted long term health care resource use for CAP outpatients
Describing the incidence and correlates of “recurrent” pneumonia in those who are not initially admitted to hospital for treatment
Examining characteristics of high risk patients who ought to have been admitted to hospital for management rather than discharged home from Emergency Departments (i.e., the low risk patient with relative hypoxemia who is better managed on an in-patient basis);
Exploring the impact of impaired functional status and other novel clinical markers that cannot be derived from administrative databases on both short and long-term outcomes
While previous studies have attempted to address some of these issues, available studies are limited by their retrospective assessments [8–12], reliance on administrative data alone, lack of measures of pneumonia severity, scope (e.g., elderly only) [9, 11, 14], relatively small sample sizes and selection bias [6, 8, 10, 13], selectivity of outcomes (e.g., treatment failure, CAP only hospitalizations) [8, 12], short duration of follow-up [6, 10, 12], and heterogeneity (hospitalized and outpatients combined) [14–16]. Moreover, none of the previous studies have had a sufficient clinically rich population-based sample size to adequately address these relevant questions. We therefore assembled this cohort to improve our current knowledge for outpatients with CAP and help frame future research.