Assessment of validity of the archived standard curve in endotoxin assay

: The archived standard curve of endotoxin assay was evaluated to be possible to be used for the endotoxin assay as the reliable standard curve, instead the standard curve was produced each time of the assay. The archived standard curve shall be produced from three standard curves for three days, following the guidance issued from FDA in 1991, and the evaluation whether the archived standard curves can be applicable to use daily was performed with the recovery rate of the concentrations obtained from the archived standard curves against the true values. The three case studies were prepared: (1) the same person, who prepared the archived standard curves, performed this assay with the standard solutions (repeatability condition with the same tester, at the same facility), (2) the person, who did not prepare the archived standard curves, performed this assay with standard solutions (reproducibility condition with the different tester and dates), (3) the same preparation as (1), but using different three lots of lysates. The recovery rates were (1) 85-127%, (2) 86-124%, (3) 64-156%, respectively. From this data, the endotoxin concentration calculated with the archived standard curves were not varied very much, compared to the true values, but further discussion are necessary when the archived standard curves would be applied in daily analysis of PET drugs, regarding the protocol, the requirement to use the archived standard curve and the daily internal control as system suitability tests.