To the Editor Faez et al1 compared the results from Western blotting analyses of antiretinal autoantibodies (ARAs) by 2 unnamed laboratories for consistency based on the molecular size of retinal proteins. They found a low concordance rate of 37%. Because details of the testing methods are not provided, the results cannot be truly compared. Since autoantibody testing is an essential procedure to confirm the diagnosis of autoimmune retinopathy, it is important that physicians understand the variables that affect test results for correct interpretation.