Prior Elicitation and Bayesian Analysis of the Steroids for Corneal Ulcers Trial

Abstract

Purpose: To elicit expert opinion on the use of adjunctive corticosteroid therapy in bacterial corneal ulcers. To perform a Bayesian analysis of the Steroids for Corneal Ulcers Trial (SCUT), using expert opinion as a prior probability.

Methods: The SCUT was a placebo-controlled trial assessing visual outcomes in patients receiving topical corticosteroids or placebo as adjunctive therapy for bacterial keratitis. Questionnaires were conducted at scientific meetings in India and North America to gauge expert consensus on the perceived benefit of corticosteroids as adjunct treatment. Bayesian analysis, using the questionnaire data as a prior probability and the primary outcome of SCUT as a likelihood, was performed. For comparison, an additional Bayesian analysis was performed using the results of the SCUT pilot study as a prior distribution.

Results: Indian respondents believed there to be a 1.21 Snellen line improvement, and North American respondents believed there to be a 1.24 line improvement with corticosteroid therapy. The SCUT primary outcome found a non-significant 0.09 Snellen line benefit with corticosteroid treatment. The results of the Bayesian analysis estimated a slightly greater benefit than did the SCUT primary analysis (0.19 lines verses 0.09 lines).

Conclusion: Indian and North American experts had similar expectations on the effectiveness of corticosteroids in bacterial corneal ulcers; that corticosteroids would markedly improve visual outcomes. Bayesian analysis produced results very similar to those produced by the SCUT primary analysis. The similarity in result is likely due to the large sample size of SCUT and helps validate the results of SCUT.

KEYWORDS::

• Bacterial keratitis
• Corneal ulcer
• Clinical trial
• Statistics
• Prior distribution

Declaration of interest: Funding for the trial was from the National Eye Institute, U10 EY015114 (Lietman). Dr Acharya is supported by a National Eye Institute K23 EY017897 grant and a Research to Prevent Blindness Award. Alcon provided moxifloxacin (Vigamox) for the trial. The Department of Ophthalmology at UCSF is supported by a core grant from the National Eye Institute, EY02162. The sponsors did not have a role in the design and conduct of the study; collection, management, analysis and interpretation of the data; and preparation, review or approval of the manuscript. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.