Abstract:
Referral bias occurs because of the clustering of patients at tertiary care centers. This may result in the distortion of observed clinical manifestations of rare diseases. This analysis evaluates the effect of referral bias on the epidemiology of infective endocarditis (IE) in the International Collaboration on Endocarditis-Prospective Cohort Study (ICE-PCS). This is a prospective multicenter cohort study comparing transferred and non-transferred patients with IE. Factors independently associated with transfer status were evaluated using multivariable logistic regression. A total of 2,760 patients were included in the analysis, of which 1,164 (42.2percent) were transferred from other medical centers. Transferred patients more often underwent surgery for IE (odds ratio [OR]∈=∈2.5; 95percent confidence interval [CI] 1.9-3.2). They were also more likely to have complications such as stroke (OR∈=∈1.5; 95percent CI 1.3-1.9), heart failure (OR∈=∈1.4; 95percent CI 1.1-1.6), and new valvular regurgitation (OR∈=∈1.3; 95percent CI 1.1-1.6). The in-hospital mortality rates were similar in both groups. Patients with IE who require surgery and suffer complications are referred to tertiary hospitals more frequently than patients with an uncomplicated course. Hospital transfer has no obvious effect on the in-hospital mortality. Referral bias should be taken into consideration when describing the clinical spectrum of IE. © 2010 Springer-Verlag.