The Association between the Establishment of a General Internal Medicine Department and an Increased Number of Blood Cultures in Other Departments: An Interrupted Time Series Analysis

Abstract

Objective The establishment of a department of general internal medicine (GIM) has been shown to improve the clinical outcomes among patients treated in GIM departments but the effect on practice patterns in other departments remains unclear. We evaluated the association between the establishment of a GIM department and the use of blood cultures, an indicator of quality of care of infectious diseases, in other departments. Methods This study was conducted between 2013 and 2017 in a community hospital which established a new GIM department in 2015, with a mandate to improve the quality of care of the hospital including infectious disease management. The primary outcome was the change in the number of blood culture episodes per calendar month in other departments before and after establishment of the GIM department. The secondary outcome was the change in the blood culture episodes per month, indexed to 1,000 patient-days, during the same time. Using 2015 as the phase-in period, interrupted time series analyses were used to evaluate the change in the outcome variables. Results In departments other than GIM, there were 284 blood cultures prior to the establishment of the GIM department (2013-2014) and 853 afterwards (2016-2017). The number of blood culture episodes in other departments increased by 10.7 (95%CI: 0.39-21.0, p=0.042) per calendar month after the establishment of the GIM department; blood culture episodes/calendar month/1,000 patient-days increased by 0.55 (95%CI: 0.03-1.07 p=0.037). Conclusion These results indicate that a GIM department in a community hospital can improve the quality of care in other departments.

Keywords: blood culture; general internal medicine; hospitalist; interrupted time series.

Figure 1.

Flow diagram of blood culture episodes. A total of 2,884 episodes were identified during the study period. Repeat blood culture episodes within 60 days (604 episodes), by the department of GIM (812 episodes), or in a day or a following day of consultation to the GIM department (38 episodes) were excluded and 1,430 episodes were identified as a number of blood culture episodes in other departments. 284 episodes were observed during the pre-GIM establishment period and 853 episodes were observed during the post-GIM establishment period. GIM: general internal medicine

Figure 2.

Change in the number of blood culture episodes per calendar month in departments other than GIM. After the establishment of GIM, the number of blood culture episodes in departments other than GIM significantly increased by 10.7 (95%CI: 0.39 to 21.0, p=0.042) episodes per calendar month. Point: the number of blood culture episodes in departments other than GIM in a month. Solid line: regression estimation of monthly numbers of blood culture episodes in departments other than GIM. Dotted line: estimation of the counterfactual if the trend in pre-GIM establishment period remained to post-GIM establishment period. GIM: general internal medicine

Figure 3.

Change in the monthly number of blood culture episodes/1,000 patient-days in departments other than GIM. After the GIM establishment, the number of blood culture episodes/1,000 patient-days in departments other than GIM significantly increased by 0.55 (95%CI: 0.03 to 1.07, p=0.037) episodes/1,000 patient-days. Point: the number of blood culture episodes/1,000 patient-days in departments other than GIM in a month. Solid line: regression estimation of monthly numbers of blood culture episodes/1,000 patient-days in departments other than GIM. Dotted line: estimation of the counterfactual if the trend in the pre-GIM establishment period remained until the post-GIM establishment period. GIM: general internal medicine