Weekend effect on blood culture contamination: an observational study at a university hospital in Japan.

Background: An association between weekend/off-hour care and unfavorable clinical outcomes has been observed, commonly called the "weekend effect." In the present study, we examined whether there was a weekend effect associated with blood culture (BC) contamination, which can lead to inappropriate medical resource consumption.

Methods: We conducted a single-center retrospective observational study using data from BC tests performed on adult patients. The primary outcome was the incidence of BC contamination, which was compared between weekend and weekday sampling groups. In a multivariable logistic analysis, we evaluated the association between weekend sampling and the incidence of BC contamination.

Results: The analysis included 7,597 weekend and 50,655 weekday BC sets from 1 January 2013 to 31 December 2019. The proportion of BC contamination during the study period was 1.15% (87/7,597) and 0.80% (405/50,655) in the weekend and weekday groups, respectively. In the logistic regression analysis adjusted for blood sampling settings, weekend sampling was significantly associated with increased BC contamination (odds ratio, 1.36; 95% confidence interval, 1.06-1.71).

Conclusions: This study highlighted a significant association between weekend blood sampling for BC and an increased incidence of contamination. To provide better-quality care, further studies evaluating the differences in staffing and blood collection processes on weekends and weekdays are warranted.