HDCN Article Review/Hyperlink

Bloom S, Fendrick AM, Chernew ME, Patel P

Clinical and economic effects of mupirocin calcium on preventing Staph. aureus infection in hemodialysis patients

Am J Kidney Dis (May) 27:687-694 1996

Medicare spends $6 billion annually on dialysis and related care. Half of all dialysis patients are nasal carriers of S. aureus infection in a given year, and half of all carriers develop S. aureus infections during a given year. Sequelae of infections are expensive.

The study is based on the premise that eliminating nasal carriage decreases the risk of S. aureus infections and therefore decreases cost. Mupirocin calcium is a new topical medication that eliminates carriage of S. aureus. The study used decision analysis to determine the cost effectiveness of three strategies of use of mupirocin calcium.

The first strategy was to screen all patients every three months for S. aureus nasal carriage and treat with intranasal mupirocin if positive. The second strategy was to treat ALL HD patients weekly with intranasal mupirocin without testing for nasal carriage. The third strategy was not to screen or treat for nasal carriage, treating secondary (primarily access site) S. aureus infections as appropriate.

The outcome was the number of infections prevented or treated and the cost attributed to the outcome. There were 1000 theoretic patients pre strategy. A decision tree was developed that incorporated the sensitivity and specificity of screening, estimated compliance and probability of S. aureus infection. These numbers were derived from the medical literature. Outcome cost was derived from the Health Care financing commission. A sensitivity analysis was then performed to determine the effect of input variables on the cost, number of infections and cost effectiveness. It was assumed that 75% of S. aureus infections were related to intranasal carriage. Worst case scenarios were tested for each alternative (i.e. the lowest rate of nasal carriage and infection, lowest rate of access loss, and highest cost of mupirocin).

The decision analysis revealed that a screening and eradication strategy relative to the non-use of mupirocin theoretically would have saved Medicare $90 million in direct medical costs in 1994 and result in a 45% reduction in S. aureus infection). The treatment of all patients regularly with intranasal mupirocin would have decreased infections by 55% relative to the non-use of mupirocin, and would have saved Medicare $130 million dollars.

Comment: The finding that weekly use of intranasal mupirocin ointment in all patients without screening of carriage of S. aureus is most cost effective creates a concern that such treatment will result in the development of resistant strains of S. aureus and may, in the end cost more. There are few data on resistance of mupirocin but this is a valid concern that must be considered when deciding which strategy is most appropriate.

As noted in the discussion, there are several pitfalls in a decision analysis, for the most part related to the initial assumptions being made. First, the role of S. aureus nasal carriage in subsequent infection is not completely clear. Second, there are discrepancies in the reported rates of S. aureus infection, carriage and sequelae. Third, the optimal regimen for treating carriage is unknown. Fourth, there is an assumption that the quality of life and daily function will improve with treatment of infection. Fifth, the study did not differentiate between non-MRSA and MRSA and the related cost differences of infection. Last, the cost of death, time off from work, etc. were not incorporated into the model.

The study was nevertheless well designed and conservative in its assumptions and should be helpful in deciding strategies for use of mupirocin calcium when it becomes available. (Catherine Stehman-Breen, UW Nephrology Clinical Research Training Group, Seattle, WA)