mice which produce measurable levels of glucose - 6 - phosphate dehydrogenase deficient red blood cells can be used as animal models to evaluate new drugs for risk of inducing hemolytic anemia in g6pd - deficient individuals , and for pre - clinical evaluation of gene therapy protocols to correct g6pd deficiency . deficient and wild - type cells can be distinguished using a tetrazolium dye , and the numbers of each type of cell counted before and after exposure of the cells to the drug or therapy .