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Abstract #9076 Published in IGR 5-2
Which endpoint: mean intraocular pressure or proportion of successful patients?
Hedman K; Taube AJournal of Glaucoma 2003; 12: 321-332
A reduction in intraocular pressure (IOP) in clinical trials can be determined through the mean IOP, through the proportion of patients who have IOP reduced to a specific target IOP, or both. Since both these possible endpoints measure the shift of two IOP distributions, the authors recommend that only one of them be tested. In general, testing the difference between mean values is much more efficient than testing the difference between proportions. However, proportions of successful patients are valuable in showing the clinical implication of a reduction in mean IOP, particularly when evaluating a moderate pressure reduction. The effect of a small mean IOP reduction on the probability to reach the target IOP is pointed out, particularly the fact that it can be substantial even if the mean reduction is smaller than the measurement error.
Dr. K. Hedman, Department of Biometrics, Pharmacia Diagnostics, S-751 82, Uppsala, Sweden. katarina.hedman@pharmacia.com