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Fig. 4. Return on investment by average annual surgical site infection (SSI) reduction using the frontier curve.
investment results was annual SSI incidence reduction followed by the annual cost of CUSP and NSQIP, respectively.
Discussion
Our study shows encouraging evidence that investments in NSQIP and CUSP have netted cost savings that may already be producing a positive return on investment at TOH. This return on investment is expected to continue in the near term assuming the reduction in SSI rate continues. The return on investment is not uniform by surgical specialty.
This variability is mostly driven by the capacity of the department or division and the relative potential of SSI improvement. Specialties with much lower numbers of surgeries per year may experience a decrease in SSI incidence rate, but because the sav- ings are in absolute dollars per patient, they may not offer suf- ficient savings for the share of investment going to that particular specialty. Additionally, specialties with historically high SSI inci- dence, can experience significant reductions in a relatively short time (eg, vascular surgery) leading to a significant ROI in those specialties. For other specialties with historically low SSI inci- dence, the rate of improvement is unlikely to be great due to the type of surgery performed or the level of care already provided. The primary return on investment analysis assumes the average
annual reduction in SSI incidence observed at TOH (0.48%) is fully attributable to the quality improvement programs initiated. Without reliable incidence data prior to NSQIP, it is difficult to test the true treatment effect of NSQIP and CUSP. However, we can estimate the minimum incidence reduction necessary given the fixed investments to date. Figure 4 displays the results of an ROI frontier analysis that finds that the minimum annual SSI incidence reduction necessary for TOH’s current investments to net a positive ROI (>1) is 0.25%. Our ROI estimate used the observed annual reduction in SSI incidence of 0.48%, leaving a 0.23% gap between the minimum reduction necessary to achieve positive ROI. Assuming the preintervention average annual reduction of SSI is <0.23%, the investments to date have netted at least a positive return on investment as of 2016. An important consideration for decision makers when con- sidering long-term investment strategies is that improvements in
SSI incidence is unlikely to remain relatively linear, and instead is likely to plateau. As shown in Table 3, those with historically low SSI incidence are already showing difficulty in continuing to improve outcomes. This is likely due to the remaining SSI cases representing a relatively small absolute number of patients and may represent the most difficult cases for which a care provider can avoid infection. The PSA is used to determine how much variability we find in
the result based on the level of uncertainty in the model para- meters. The analysis finds a relatively low probability (43%) that the quality improvement program to date has a positive return on investment for the hospital. This is predominantly due to the wide confidence interval of cost per SSI case, partly due to the sig- nificant variation in the severity of SSI that requires different levels of hospital resources. Previous research has shown the significant impact of SSI on a patient’s length of stay and overall costs of care,3,4 so there is a reasonable expectation that the confidence interval overstates the possibility that patients with SSI are in fact cost saving. For this reason, we believe the ROI frontier curve is more directly applicable to the hospital’s consideration of whether the investments to date have already generated a positive return on investment. Few published studies have assessed the cost or cost- effectiveness of NSQIP and/or CUSP-like interventions to date. The assessment methods used in previous studies were extremely varied. Only 2 studies conducted cost-effectiveness analyses7,8; 6 studies performed a cost analyses.7,9–13 Among these studies, 6 studies7–9,11,13 found that quality improvement programs resulted in savings to the hospital; however, only one study detailed the type of interventions that took place other than NSQIP.7 In 4 cases, the program under evaluation was NSQIP itself.8–10,13 Also, 2 studies used the American College of Surgeons (ACS) NSQIP ROI calculator to determine net savings.8,13 This online calculator uses an average cost of SSI based on the entire ACS hospital network, making it highly unreliable to a specific hospital’s circumstance. Only 4 studies7–10 performed a sensitivity analysis, of which only 1 study10 reported the possibility that savings from NSQIP could be potentially not cost saving. Methodologically, the closest publication to our own analysis
is an Albertan study across 5 hospital sites that estimated a NSQIP and associated SQIP initiatives’ return on investment of
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