ELISA reading range - ELISA assay (May/16/2005 )

HI, whenever I run an ELISA assay with a normal and treated plasma, my OD readings are very close to each other. I.e., 1.12 for normal plasma and 1.11 for treated plasma. The expected range of readings are approximately 1.5 and 0.8 respectively-- the numbers are not very important; but they should be clearly separated. When others do the same assay with same reagents their ELISA OD readings are more like the expected. Can anyone give me any idea as to what I'm doing wrong here?

i'm sure you are but are you using the right wavelengths? or depending on your machine do you have the right wavelengths available?