Diagnostics based on tetrazolium compounds
A reagent is suitable for measuring the concentration of an analyte in a hemoglobin-containing biological fluid, such as whole blood. The reagent comprises a flavin-dependent enzyme that has specificity for the analyte, a flavin cofactor if, and only if, a flavin is not bound to the enzyme, a tetrazolium dye precursor, an electron transfer agent, and a nitrite salt. The reagent causes dye formation that is a measure of the analyte concentration. The nitrite salt suppresses interfering dye formation caused non-enzymatically by the hemoglobin. Preferably, the reagent is used in a dry strip for measuring glucose in whole blood.
1. A reagent for measuring a concentration of an analyte in a hemoglobin-containing biological fluid, comprising
a) a flavin-dependent enzyme that has a flavin bound to it and that has specificity for the analyte,
b) a tetrazolium dye precursor,
c) an electron transfer agent, and
d) a nitrite salt.
2. The reagent of claim 1 in which the analyte is glucose and the enzyme is glucose oxidase.
3. The reagent of claim 1 in which the dye precursor is water-soluble.
4. The reagent of claim 1 in-which the electron transfer agent comprises phenazine methosulfate (PMS)or an analog thereof.
5. The reagent of claim 1 further comprising a divalent metal stabilizer.