Influence of referral bias on the clinical characteristics of patients with Gram-negative bloodstream infection

M. N. Al-Hasan, J. E. Eckel-Passow, L. M. Baddour

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Referral bias can influence the results of studies performed at tertiary-care centres. In this study, we evaluated demographic and microbiological factors that influenced referral of patients with Gram-negative bloodstream infection (BSI). We identified 2919 and 846 unique patients with Gram-negative BSI in a referral cohort of patients treated at Mayo Clinic Hospitals and a population-based cohort of Olmsted County, Minnesota, residents between 1 January 1998 and 31 December 2007, respectively. Multivariable logistic regression analysis was used to determine factors associated with referral. Elderly patients aged ≥80 years with Gram-negative BSI were less likely to be referred than younger patients [odds ratio (OR) 0·43, 95% confidence intervals (CI) 0·30 - 0·62] as were females (OR 0·63, 95% CI 0·53 - 0·74). After adjusting for age and gender, bloodstream isolates of Escherichia coli (OR 0·50, 95% CI 0·43 - 0·58) and Proteus mirabilis (OR 0·49, 95% CI 0·30 - 0·82) were underrepresented in the referral cohort; and Pseudomonas aeruginosa (OR 2·26, 95% CI 1·70 - 3·06), Enterobacter cloacae (OR 2·31, 95% CI 1·53 - 3·66), Serratia marcescens (OR 2·34, 95% CI 1·33 - 4·52) and Stenotrophomonas maltophilia (OR 17·94, 95% CI 3·98 - 314·43) were overrepresented in the referral cohort. We demonstrated that demographic and microbiological characteristics of patients with Gram-negative BSI had an influence on referral patterns. These factors should be considered when interpreting results of investigations performed at tertiary-care centres.

Original languageEnglish (US)
Pages (from-to)1750-1756
Number of pages7
JournalEpidemiology and Infection
Issue number11
StatePublished - Nov 2011


  • Bacteraemia
  • Gram-negative
  • Rochester Epidemiology Project
  • epidemiology
  • population-based
  • selection bias

ASJC Scopus subject areas

  • Epidemiology
  • Infectious Diseases


Dive into the research topics of 'Influence of referral bias on the clinical characteristics of patients with Gram-negative bloodstream infection'. Together they form a unique fingerprint.

Cite this