Discussion
This study of 35,363 surgical patients at 52 different hospitals in the state of Michigan showed (1) that the incidence of postoperative CDI, although uncommon overall, was greater in lower-extremity amputations, gastric or esophageal operations, and bowel resection or repair; (2) that the use of intravenous prophylactic antibiotics was not associated with CDI, and (3) that CDI was significantly associated with organizational resource utilization metrics, as risk adjusted readmission rates and LOS were more than double in patients with CDI.
The overall incidence rate of CDI of 0.51% is comparable to other published incidence rates. However, the recent time frame, diverse surgical population, and prospective data collection with 30-day follow-up are unique to this report. During the year the data were collected (2012–2013), the majority of Michigan hospitals had adopted PCR diagnostic testing methodology, which is more sensitive and specific and therefore has fewer false-positive results. Furthermore, our study reflects the contemporary nature of the CDI epidemic in this cohort of surgical patients, most likely involving a substantial number of cases caused by epidemic strains of C. difficile, including the NAP1/BI/027 strains. Nonetheless, direct comparison of CDI rates to other surgical populations and reports is difficult because the incidence and consequence of CDI are not uniformly defined, reported, nor calculated, especially among administrative databases.
The present study demonstrates that CDI incidence rates vary significantly between procedures. Similar to the work by Zerey et al, patients undergoing gastric, small bowel, or colonic resection were at greater risk for CDI. The highest incidence, however, was in patients undergoing a lower-extremity amputation, (2.6%; aOR, 3.5). These patients tend to be in and out of the hospital very frequently before ultimately undergoing an amputation or to have frequent courses of therapeutic antibiotics, thereby increasing their likelihood of developing this infection. On the other hand, the low incidence of CDI among patients who underwent endocrine operations or hysterectomy is not surprising, given that most of them have a short and limited exposure to the healthcare setting. Although the majority (95%) of patients developing CDI had some form of exposure to antibiotics, prophylactic antibiotics per se were not associated with CDI in this study, confirming the findings from a prior study limited to colectomy patients. While there was a trend for patients who were receiving therapeutic antibiotics for other indications to develop CDI, this trend did not reach statistical significance in the multivariable analysis. It is important to note, however, that patients undergoing higher-risk surgical operations are also more likely to be exposed to preoperative antibiotics depending on their indication (eg, colectomy for diverticulitis), thereby contributing to the overall risk.
From a human and financial perspective, CDI is a costly infection. The financial costs of a CDI episode for a hospital are estimated to be approximately $10,000. The human cost, is more difficult to quantify but no less important. Together these costs create a preventable burden that could be a rich target for quality improvement and patient care outcomes. Our data confirm that CDI has significant downstream strains on resource utilization. The readmission rate was more than double compared with those patients without CDI. This is not surprising given the deconditioning, dehydration and overall fatigue that accompany CDI in patients already debilitated by recent surgery. With the continued rise in CDI and stricter financial penalties in 2017, there is a strong business case for making an investment in strategy and resources for CDI prevention.
Because surgical patients already carry twice the burden of HAI than their medical counterparts, administrators may want to consider pathogen-directed or vertical interventions to target specific surgical patients undergoing high-risk procedures. Pathogen-directed and vertical interventions are designed to prevent transmission of specific pathogens causing the infection; they are developed to combat the unique epidemiological characteristics of the organism. In contrast, the non-pathogen–directed, or horizontal, intervention approach attempts to reduce the rates of all infections from all pathogens simultaneously. An example of a pathogen-directed approach is the success of the rapid screening and decolonizing of nasal carriers of Staphylococcus aureus upon admission to reduce surgical site infections. Proponents of the non-pathogen–directed approaches report similar success rates using horizontal interventions with similar success rates at a significant cost savings. Although effective horizontal successes have been reported in relation to CDI, the severe financial penalties for CDI may drive the more aggressive and focused preventative intervention strategies that pathogen-directed interventions deliver (ie, preemptive isolation, private rooms, etc.).
This study has several inherent limitations. Primary among them are the shortfalls in the definition and interpretation of CDIs. Our CDI diagnosis included only the results of confirmed laboratory diagnosis of C. difficile toxin assay or culture. It did not detect those patients who may have had received empiric treatment, which may have led to underestimation of CDI in this cohort. Additionally, this study did not account for those patients who were colonized with C. difficile (tested positive) but did not exhibit symptoms (not infected). The overall influence of these patients that are colonized but not infected are believed to be minimal because they would not qualify for testing without the requisite diarrhea episodes. In addition, because diagnostic detection techniques were different at each of the 52 locations, underestimation or overestimation of CDI could confound the results. However, the data collection occurred during 2012, and it is likely that most hospitals had updated their diagnostic testing to the more specific and sensitive PCR methodology. On the other hand, we captured all patients who had a positive result within 30 days of their index operation, which is unique to this report; time lapse during follow-up represents one of the major limitations of other studies using discharge data. Finally, we excluded patients who had a positive result within 72 hours, thereby truly capturing the incidence of a hospital-acquired infection.
In conclusion, the present study shows (1) that postoperative CDI rates vary between procedures with up to a 5-fold increased risk in lower-extremity amputations, (2) that the use of intravenous prophylactic antibiotics was not significantly associated with CDI, and (3) that CDI was significantly associated with resource utilization metrics, as risk adjusted readmission rates and LOS were more than double in patients with CDIs. With new reimbursement legislation and penalties on the horizon, the results from this study can help inform clinicians and administrators regarding timely and practical implications to target surgical patient populations at high risk for CDI and downstream resource utilization.