Infection Control & Hospital Epidemiology
Table 3. Mean Overall Total 1-Year Costs Including Interquartile Range (IQR) for Infected and Noninfected Cohorts Overall and by Subgroup Overall Costsa
Infection Related Costsb Variable All Patients Age <65 y Age ≥65 y
Joint replacement Hip
Knee
Elixhauser comorbidities 0
1 or 2 ≥ 3 Staphylococcus aureus Other pathogens
aMann-Whitney U P values <.001. bMann-Whitney U P values <.001.
economic burden from SSI following hip arthroplasty.21 While these studies using a matched design were much smaller than our study, they also noted significant differences in cost and length of stay for infected and noninfected patients.20,21 Using the average 1-year total healthcare costs, in Alberta we
infected joints,15 which is consistent with our observation that patients with S .aureus SSI had higher mean 1-year costs compared to all other pathogens, $108,175 versus $87,317 (P = .077) (US$ 77,340 vs US$ 62,427), though it did not reach sig- nificance. When only the infection finding codes were used, patients with S. aureus SSIs did have significantly higher mean 1-year costs compared to all other pathogens: $83,638 versus $62,228 (P = .006) (US$ 59,797 vs US$ 44,490). Because
spend ~$8.3 million annually on patients who develop complex SSI following primary hip and knee arthroplasties compared to the $1.67 million we would spend had those patients not developed a complex SSI. If the mean annual costs and infection rate (1.04%) is extrapolated to all of Canada, where there are ~100,000 arthro- plasties annually,1 $133.5 million would be spent on patients annually who acquire a complex SSI versus $28 million for the same number of patients with no infection. If we apply the same complex infection rate of 1.04% and costs to the United States, where there are 700,000 hip and knee arthroplasties annually,3 the annual expenditure would be ~$694 million (US$ 496 million) to manage the SSIs, compared to $145 million (US$ 104 million) that would be spent had no infection developed. Staphylococcus aureus can be very difficult to eradicate from
S. aureus is the most commonly isolated causative organism for complex SSI following hip and knee arthroplasty, targeting preventative efforts toward reducing this organism may be worthwhile because colonization with S. aureus is a risk factor for SSI.22 Decolonization protocols studied previously in joint arthroplasty do demonstrate a reduction in SSIs,23 and given the high cost of S. aureus SSI, the use of decolonization protocols may be cost-effective. Our study has several strengths. We performed a population-
based study in a province of >4 million people, identifying all primary hip and knee replacements and all subsequent complex SSIs that occurred within 3 months of arthroplasty. We used high- quality microcosting data, which is not commonly done, and our estimates are likely generalizable to the rest of Canada. While costs are not always directly comparable between countries, these find- ings can still be used as a guide. Our study does have limitations. We have likely underestimated the cost differences across infected and noninfected patients because we did not include elements such as physician claims. Additionally, we did not consider costs borne by the patients themselves. For patients who are employed, there are costs associated with lost productivity, and for all patients with infections, there are additional patient-borne costs for outpatient antibiotics, rehabilitation, and costs related to travel for medical care. Finally, superficial SSIs were absorbed into the noninfected cohort, so itis possible that costdifferences would have been even greater between the infected and noninfected cohorts had super- ficial infections been considered separately.
Infected Cohort, $ (IQR) 95,321
(49,623–120,636) 90,717
(42,827–122,029) 98,797
(55,351–120,447) 98,047
(51,938–124,428) 91,822
(46,204–110,921) 78,721
(40,752–100,151) 93,103
(49,507–121,518) 116,002
(61,980–141,308) 108–175
(50,794–150,830) 87, 317
(49,570–109,139)
Non-Infected Cohort, $ (IQR) 19,893
(12,610–19,723) 17,787
(12,467–17,877) 21,630
(12,762–21,579) 20,584
(13,042–19,906) 19,444
(12,287–19,622) 17,903
(12,392–17,910) 20,967
(12,743–20,564) 22,808
(13,116–23,148) …
…
Infected Cohort, $ (IQR) 70,144
(35,923–86,368) 68,356
(35,487–85,586) 72,020
(36,148–88,389) 72,060
(41,582–89,042) 68,369
(31,868–82,968) 58,510
(31,868–76,321) 68,401
(35,560–81,718) 85,839
(49,000–89,656) 83, 638
(41,492–103,670) 62, 228
(34,780–78,210)
Noninfected Cohort, $ (IQR) 13,195
(10,269–13,049) 12,534
(10,269–12,575) 13,740
(10,269–13,616) 14,132
(11,434–13,783) 12,586
(10,190–12,432) 12,287
(10,269–12,381) 13,490
(10,269–13,420) 14,836
(10,597–14,845) …
…
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