Risk factors for hospital-acquired urinary tract infection in a large English teaching hospital: a case-control study.

About 10% of patients in hospital develop a hospital-acquired infection (HAI); the most commonly affected site is the urinary tract. Many studies have examined risk factors for HAI but few have adjusted for confounding and interaction. We performed a prospective case-control study on six acute wards of a busy English teaching hospital to assess risk factors for hospital-acquired urinary tract infection (HAUTI). Over a 2-year period, 136 cases were identified (2.8% of all patient episodes) along with 408 controls. Multiple logistic regression revealed that female sex, increased length of stay, elective admission, surgical operation, and transurethral and repeated intermittent catheterization were all significant independent risk factors for HAUTI. However, specialty of admission was also a significant risk factor when added to the model and, under these conditions, only length of stay and catheterization also remained significant. We detected significant interactions suggesting that the risk of HAUTI is maximal among women undergoing elective surgery, especially those who are catheterized; however, the overall risk of HAUTI among patients admitted electively was greater than for patients admitted as emergencies.