The International Community-Acquired Pneumonia (CAP) Collaboration Cohort (ICCC) study: rationale, design and description of study cohorts and patients

OBJECTIVE: To improve the understanding of the determinants of prognosis and accurate risk stratification in community-acquired pneumonia (CAP). DESIGN: Multicentre collaboration of prospective cohorts. SETTING: 6 cohorts from the USA, Canada, Hong Kong and Spain. PARTICIPANTS: From a published meta-analysis of risk stratification studies in CAP, the authors identified and pooled individual patient-level data from six prospective cohort studies of CAP (three from the USA, one each from Canada, Hong Kong and Spain) to create the International CAP Collaboration Cohort. Initial essential inclusion criteria of meta-analysis were (1) prospective design, (2) in English language, (3) reported 30-day mortality and transfer to an intensive or high dependency care and (4) minimum 1000 participants. Common baseline patient characteristics included demographics, history and physical examination findings, comorbidities and laboratory and radiographic findings. PRIMARY AND SECONDARY OUTCOME MEASURES: This paper reports the rationale, hypotheses and analytical framework and also describes study cohorts and patients. The authors aim to (1) compare the prognostic accuracy of existing CAP risk stratification tools, (2) assess patient-level determinants of prognosis, (3) improve risk stratification by combined use of scoring systems and (4) understand prognostic factors for specific patient groups. RESULTS: The six cohorts assembled from 1991 to 2007 included 13 784 patients (median age 71 years, 54% men). Aside from one randomised controlled study, the remaining five were cohort studies, but all had similar inclusion criteria. Overall, there was 0%–6% missing data. A total of 6159 (44%) had severe pneumonia by Pneumonia Severity Index class IV/V. Mortality at 30 days was 8% (1036). Admission to intensive care or high dependency unit was also 8% (1059). CONCLUSIONS: International CAP Collaboration Cohort provides a pooled multicentre data set of patients with CAP, which will help us to better understand the prognosis of CAP.