Standardized viral hemagglutination and hemagglutination-inhibition tests. I. Standardization of erythrocyte suspensions.

A spectrophotometric procedure for standardizing red blood cell suspensions for use in viral hemagglutination tests is described. The procedure is based on highly reproducible cyanmethemoglobin absorbance readings at 540 nm on any suitable spectrophotometer. Target values for milligrams of cyanmethemoglobin per 100 ml are given for the red cell suspensions of all mammalian and avian species employed in viral hemagglutination tests. By use of these values and a cyanmethemoglobin standard curve for a particular photometer, approximate 4% erythrocyte suspensions can be diluted to any lesser concentration. Coefficients of variation for the various diluted suspensions range from 4 to 7%.