... control serum and 2 wells for positive control serum, 100 μ L/well. S et one blank control well, ... add 100 μL sample diluent. Similarly, dilute the sample s at 1:40 with the sample diluent,100 μLeach well ... well, and test the OD630 value on the spectrophotometer. For the assay to be valid, the positive control ... equal to 0.4, and the negative control wells ’ average OD630 value is less ...