Identifying the risk factors for catheter-associated urinary tract infections: a large cross-sectional study of six hospitals

Abstract

Motivation: Catheter-associated urinary tract infections (CAUTI) are a common and serious healthcare-associated infection. Despite many efforts to reduce the occurrence of CAUTI, there remains a gap in the literature about CAUTI risk factors, especially pertaining to the effect of catheter dwell-time on CAUTI development and patient comorbidities.

Objective: To examine how the risk for CAUTI changes over time. Additionally, to assess whether time from catheter insertion to CAUTI event varied according to risk factors such as age, sex, patient type (surgical vs medical) and comorbidities.

Design: Retrospective cohort study of all patients who were catheterised from 2012 to 2016, including those who did and did not develop CAUTIs. Both paediatric and adult patients were included. Indwelling urinary catheterisation is the exposure variable. The variable is interval, as all participants were exposed but for different lengths of time.

Setting: Urban academic health system of over 2500 beds. The system encompasses two large academic medical centres, two community hospitals and a paediatric hospital.

Results: The study population was 47 926 patients who had 61 047 catheterisations, of which 861 (1.41%) resulted in a CAUTI. CAUTI rates were found to increase non-linearly for each additional day of catheterisation; CAUTI-free survival was 97.3% (CI: 97.1 to 97.6) at 10 days, 88.2% (CI: 86.9 to 89.5) at 30 days and 71.8% (CI: 66.3 to 77.8) at 60 days. This translated to an instantaneous HR of. 49%-1.65% in the 10-60 day time range. Paraplegia, cerebrovascular disease and female sex were found to statistically increase the chances of a CAUTI.

Conclusions: Using a very large data set, we demonstrated the incremental risk of CAUTI associated with each additional day of catheterisation, as well as the risk factors that increase the hazard for CAUTI. Special attention should be given to patients carrying these risk factors, for example, females or those with mobility issues.

Keywords: catheter-related infections; infection control; patient safety; quality in health care.

Figure 1

Kaplan-Meier survival curve for all catheterisations. The x-axis begins on day 3 as only patients who had catheters inserted for at least two full days can develop a catheter-associated urinary tract infection, according to the Centers for Disease Control and Prevention definition. The number of patients at risk after each 20 day interval is represented in the table below the figure. Minimal survival rate of. 66 is reached on day 73 when 23 patients remain in the study sample.

Figure 2

Instantaneous hazard curve. The instantaneous hazard is derived using the Kaplan-Meier estimates. The B-spline smoothing model estimates that instantaneous hazard to be the highest at around 40 days. The graph is truncated after the last catheter-associated urinary tract infection event occurs.

Figure 3

Infection-free survival stratified by sex and age group. (A) Kaplan-Meier survival curve comparing adult (18+ years old) versus paediatric (0–17 years old) groups (log-rank p=0.007). (B) Kaplan-Meier survival curve comparing men and women (log-rank p<0.0001).

Figure 4

Hazard ratios derived from the Cox proportional hazards model. The presence of a comorbidity is represented by a ‘1’, that is, 1771 patients had a severe liver disease diagnosis. Only comorbidities that were found to be significant in a univariate analysis are included in the multivariate model and figure.