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Study points to savings with staph screening before joint replacement

By: Terry Stanton

By Terry Stanton

The high cost of revision joint arthroplasty can make it worth an institution’s while to implement an infection-screening program, even if the program results in only a modest reduction of surgical site infections, according to a paper presented Friday by James D. Slover, MD.

Dr. Slover and his colleagues at the NYU Hospital for Joint Diseases sought to determine if preoperative universal screening for Staphylococcus aureus and a decolonization program in patients undergoing hip or knee replacement would achieve a reduction in morbidity and associated costs sufficient to justify the expense of the program. Working with an assumed cost of about $15,000 for a primary knee replacement and $70,000 for a septic revision procedure, they anticipated that the cost of implementing a universal screening program would be recouped by a small decrease in the infection rate, but they sought to establish more precise parameters by which a program may be deemed cost-effective.

For the study, all patients in the preadmission testing program for primary hip or knee replacement participated in the screening. All were given a prescription for mupirocin treatment, and a nasal culture was obtained from them preoperatively. If the patient complied with the prescription and had a culture that was positive for methicillin-sensitive S. aureus (MSSA), he or she received traditional perioperative prophylaxis with a cephalosporin. If a compliant-patient nasal culture was positive for methicillin-resistant S. aureus (MRSA), the patient received perioperative treatment with vancomycin rather than a cephalosporin.

A noncompliant patient with positive culture for MRSA received perioperative treatment with vancomycin and mupirocin, while a noncompliant patient positive for MSSA received traditional prophylaxis with a cephalosporin and perioperative treatment with mupriprocin. Patients negative for MRSA and MSSA received cephalosporin perioperatively.

Dr. Slover said he and his colleagues have not tracked enough patients to draw definitive conclusions about the impact on infections and the resulting cost savings—a process that “will take some time given the numbers that will be needed to have statistical significance.” However, the preliminary data from 1,300 patients indicate that the screening program reduced the infection rate from 1.5 percent to 1.0 percent, said co-author Joseph A. Bosco, MD. The 1.5 percent base figure is consistent with the rates of infection reported in the literature, as are the assumed costs for the surgical procedures and an estimated $105 per patient cost for the screening and prophylaxis measures.

Dr. Bosco explained that in a hypothetical group of 1,000 patients, these results mean that a screening program will prevent 5 infections. With a screening cost of $105,000, “it costs $21,000 to prevent an infection that costs $75,000 to treat. This is cost-effective,” he said.

In the paper, the authors presented a model demonstrating the reduction a screening program needs to achieve to be cost-effective. The model shows that if a program reduces infection rates by more than 40 percent—i.e, achieving a revision rate of 0.6 or less—then it is cost-effective in all cases. Other scenarios can be seen in a graph (Figure 1) that shows parameters for which screening programs save costs or do not. It indicates, for example, that a program that achieves a 30 percent reduction in infection is cost-effective if the cost of treating an infected patient is greater than $30,000.

Because of the relatively low cost per patient for screening and prophylaxis, Dr. Slover said that “any statistically significant reduction will be highly cost-effective. If we can establish that, then screening and decolonization is likely to become a widely used preoperative infection control intervention.”

The other authors of “Cost-effectiveness of Screening and Decolonization of S. aureus for Reducing Surgical Infections” are Janet Haas, MD, Michael Phillips, MD, and Igor Immerman, MD.

Disclosure information: Dr. Slover—Smith & Nephew, Stryker; Dr. Haas—Otsuka Pharmaceutical Co. Ltd.; Dr. Bosco—Ortho McNeil Janssen, AO, Arthrex, DePuy, EBI, Exactech, Hand Innovations, Mitek, Small Bone Innovations, Smith & Nephew, Stryker, and Synthes. Drs. Phillips and Immerman reported no conflicts.

Terry Stanton is senior science writer for AAOS Now. He can be reached at tstanton@aaos.org.

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