Levels of a number of metabolites as well as a number of enzymes in body fluids are indicative of disease conditions. Many of the enzymatic reactions mentioned above have been used in solution clinical assays as well as in test strips.446,497-508’512-515 Assays for hydrogen peroxide and the enzyme peroxidase using NADH and a tetrazolium salt have been de — scribed.509,510 Assays of exogenous substances (e. g., drugs or their metabolites) also utilize this chemistry. The determination of alcohol using alcohol dehydrogenase is an example.511 As mentioned above, the assay of enzyme levels can also be achieved using tetrazolium salts.516-520
Tetrazolium salts can be reduced nonselectively by many endogenous reductants such as thiol-containing proteins, as well as exogenous ones such as ascorbic acid.521 -523 This can lead to serious interferences and several measures have been described to reduce or eliminate their effect.524,525,650
In microbiology, the reduction of tetrazolium salts has been used to detect the presence of microorganisms in serum526-532 The use of tetra — zolium salts in hematology has been reviewed.533,534 They have been used to measure enhanced phagocytic ability in neutrophils535,536 as well as to test for the presence of infectious agents.537-541 They have also been used to evaluate granulocyte function.542 Their use has been proposed as a pollen allergy indicator.543,545 The reduction of tetrazolium salts by enzymes in living cells is a proposed method to study the chemoselectivity of human tumor cells, the effect of various therapies, and the mode of action of drugs.545-550