Abstract: A composition, test device, method of making a test device and process for bilirubin-resistant determination of an analyte selected from uric acid or cholesterol in a fluid sample are disclosed. More particularly, the composition is of the type comprising means responsive to the presence of the particular analyte to be determined in the sample, a phenol and 4-aminophenazone to which resistance to interference by bilirubin is imparted by inclusion therein of reagent means comprising a ferrocyanide ion. The uric acid or cholesterol responsive means is preferably of the type which determines peroxides formed from enzymatic conversion of the analyte. The composition can optionally be incorporated with a carrier to provide a test device.