December 2009

 

CATARACT/ IOL

 

More insights into endophthalmitis


by Matt Young EyeWorld Contributing Editor

   

Two views of post-op endophthalmitis [For both images] Source: Nick Mamalis, M.D

Although ophthalmologists want the best visual results for their patients, there are pros and cons to consider during a course of treatment, and cost is a factor that can swing decisions. Even regarding prevention of a visually threatening disease such as endophthalmitis, cost must be considered. Ayman Naseri, M.D., Department of Ophthalmology, San Francisco Veterans Administration Medical Center, San Francisco, and colleagues, recently took that consideration to the extreme, evaluating the efficacy threshold necessary for antibiotics to achieve cost-effective equivalence with intracameral cefuroxime, which Dr. Naseri noted “is the only method to date whose efficacy (attributable reduction in incidence of endophthalmitis after cataract surgery) has been established and estimated by large, prospective clinical studies.”

Unlike most research into endophthalmitis, conclusions heavily considered costs of treatment, using research data to show how expensive the latest antibiotic treatments can be even if they are theoretically better than intracameral cefuroxime. “A sensitivity analysis reveals that even in the worst case scenario for intracameral cefuroxime efficacy and with a 50% reduction in the cost of 4th-generation fluoroquinolones, gatifloxacin and moxifloxacin would have to be 9 times more effective than intracameral cefuroxime to achieve cost-effective equivalence,” Dr. Naseri reported in the study, which was published in the June 2009 online edition of Ophthalmology. In Dr. Naseri’s complex analysis, gatifloxacin (Zymar, Allergan, Irvine, Calif.), moxifloxacin (Vigamox, Alcon, Fort Worth, Texas), and other antibiotics were assumed to be completely effective in preventing endophthalmitis, allowing the study to determine maximum possible cost effectiveness of agents besides intracameral cefuroxime.

Prophylaxis: How much is it worth?

Dr. Naseri’s study used a lot of assumptions, but they were necessary ingredients for performing the required calculations. The formulas and factors involved are too detailed to cover here, but a brief overview should help put the results in context. Interested readers are urged to consult the full study.

Antibiotics analyzed included intracameral cefuroxime, subconjunctival cefazolin, topical gatifloxacin, topical moxifloxacin, intracameral moxifloxacin, topical ofloxacin, topical ciprofloxacin, topical polymixin/trimethoprim, subconjunctival gentamicin, topical sulfacetamide, and a combination of certain agents.

Antibiotic costs were obtained from average wholesale prices from the Red Book 2007 edition. Many assumptions were made about preparation labor and supplies consumed, but in the end, Dr. Naseri assigned a cost value of $2.83 to the use of intracameral cefuroxime per person and $57.60 to the use of gatifloxacin per person, with many other cost values in between. “The cost-effectiveness ratio we computed was simply the expected cost difference per person for each prophylaxis regimen divided by the expected number of cases prevented (per person),” Dr. Naseri noted. “The expected cost difference per person is the expected cost given the prevention regimen minus the expected cost without the prevention regimen.”

The costs and likelihood of endophthalmitis also was factored into the analysis. Based on previous literature, the study used 0.247% as the endophthalmitis rate.

Based on a hypothetical cohort of 100,000 eyes, Dr. Naseri concluded that intracameral cefuroxime provides net cost savings of about $480,000 due to endophthalmitis prevention, although 45 cases were still likely to have occurred. “None of the fluoroquinolones were cost saving, even assuming that all potential cases of endophthalmitis were averted by their use,” Dr. Naseri reported. “When we exclude treatment costs saved owing to cases of endophthalmitis prevented, the cost-effectiveness ratio of intracameral cefuroxime is $1,403 per case of postoperative endophthalmitis prevented.”

Here are other interesting statistics arising from the study: Only if topical ciprofloxacin prevented 8.79 times as many endophthalmitis cases as intracameral cefuroxime would it have the same cost-effectiveness.

Topical ofloxacin, moxifloxacin, and gatifloxacin would have to avert 2.9, 4.72, and 4.94 times as many cases of disease to have the same cost-effectiveness.

Only topical sulfacetamide, subconjunctival gentamicin, subconjunctival cefazolin, and intracameral cefuroxime were found to be cost savers per case prevented. “In no scenario is a fluoroquinolone cost saving,” Dr. Naseri noted. “Even if topical 4th-generation fluoroquinolones could reduce the postoperative endophthalmitis infection rate to zero, their expected cost per case of endophthalmitis prevented would be between $18,474 and $19,527.”

Dr. Naseri did, however, caution against choosing an antibiotic based solely on cost. “Although our results provide a framework for evaluating multiple treatment modalities, we caution against absolute statements favoring any clinical treatment based solely on cost to the exclusion of effectiveness and other clinical considerations,” Dr. Naseri concluded. William B. Trattler, M.D., director, Cornea, Center for Excellence in Eye Care, Miami, further cautioned that antibiotic choice is about much more than just cost consideration, and he takes issue with the use of intracameral cefuroxime as endophthalmitis prevention. “The problem with cefuroxime is that it doesn’t cover the bugs we’re most worried about with endophthalmitis,” Dr. Trattler said. Years ago, when the best research on intracameral cefuroxime was being conducted, methicillin-resistant Staphylococcus aureus (MRSA) was much less common, Dr. Trattler said. But new research has found that 40% of all Staphylococcus organisms are methicillin resistant, Dr. Trattler said “Cefuroxime doesn’t have the coverage” to fight these bugs, Dr. Trattler said. “It may be cheaper, but the question is, does it work?”

Editors’ note: Dr. Naseri has no financial interests related to this study. Dr. Trattler has financial interests with Allergan (Irvine, Calif.).

Contact information

Naseri: ayman.naseri@va.gov
Trattler: 305-598-2020, wtrattler@gmail.com

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