[Direct assay for urine cortisol with cortisol kit [TFB]].

We examined Cortisol Kit [TFB] for direct assay of urine cortisol. And the multiplication by dilution factor of urine cortisol values in this kit was examined. The coefficient of correlation of cortisol levels (46 urine samples) between Cortisol Kit [TFB] and Chemilumi ACS-Cortisol II, which is another kit for direct assay of urine cortisol, was r = 0.858, y = 1.86x + 38.2 (p < 0.001). There were differences between the both cortisol levels of each urine sample in spite of the good coefficient of correlation. The urine cortisol values obtained from the standard curve in addition of 50 microliters of zero standard were 50-80% of the values obtained from the standard curve in the package insert. These results suggest that the specificity of the antibodies of both direct assay kits for urine cortisol may be different each other, and the multiplication by 1.09, the dilution factor due to the addition of zero standard to only urine sample, is unnecessary although it is indispensable for urine samples to add zero standard. Cortisol Kit [TFB] was very convenient for its easy assay procedure and short incubation.