A spiked aliquot of the test sample (or dilution) may be prepared as follows: Method #1: Transfer 10 ml of a 2.0 EU/ml solution into each of the appropriate PPC wells in the 96-well plate or reaction tubes. Each well will now contain 0.02 EU/well. To these wells or tubes add 50 ml of test sample (or dilution). Mix gently. The PPC wells now contain a 0.4 EU/ml spike. Method #2: Place 50 ml of test sample (or dilution) into the appropriate PPC wells in the 96-well plate or reaction tubes. To these wells, add 10 ml of a 2.0 EU/ml solution. Each well will now contain 0.02 EU/well, or 0.4 EU/ml spike. Mix gently. Calculate the amount of endotoxin recovered from the spiked samples versus un-spiked samples. If the recovered amount is outside of 0.4 EU/ml ± 25%, then your sample is interfering with the assay at that dilution. If the test sample is found to be inhibiting the QCL-1000 reaction, the sample may require further dilution until the inhibition is overcome. If the test sample is found to be enhancing the QCL-1000 reaction, your sample may require dilution or pre-treatment (such as heat inactivation) to overcome the interference.