To the Editor:— Your editorial (The Journal, April 21) calling attention to the methylene blue test for bilirubin will be of value in that numerous papers or communications will soon appear denying the specificity of such a test. On theoretical grounds it was apparent that the green color which results when methylene blue is added to urine is merely related to the subtraction of colors from the visible spectrum by the substances involved in the test. No reaction takes place, because the test may be duplicated by merely holding a blue glass filter (Corning number 4303) in front of a test tube containing either yellow urine or a solution of bilirubin. That this test is nonspecific and will be of little value may be seen from these spectroscopic observations and chemical procedures. Methylene blue appears blue because it has a strong absorption band in the red end of the spectrum