CHROMOGENIC ENDOTOXIN ASSAYS. - FURTHER METHOD DEVELOPMENT AND PRACTICAL EXPERIENCE

A kit for the determination of endotoxin by using Lumulus lysate (LAL) and a chromogenic substrate has now been available for three years. Here we will summarize the present status concerning its usefulness in the control of parenteral drugs, in hygienic control and in clinical diagnosis.

The wide variation of uses, demands considerable work for method adaptation to the various types of specimen and laboratory. Almost all samples have to be pretreated to become compatible with the reagents in the assay. It has also been found to be important to consider variousdemands depending on the number of samples, how fast the answer is wanted, simplicity and accuracy of the assay that is needed as well as equipment available. In some cases a single screening test is required. Then a tube with 100 pi of LAL reagent can be taken from the freezer. The other extreme is the determination of hundreds of samples in each series. Then microplates and suitable readers can be of great help. Several other procedures used on special occasions allowing e.g. wide assay range or low reagent cost will also be presented.

Manual and microplate procedures have been found suitable and can be made safe regarding contamination and losses of endotoxin. Single stage and micro methods have been tested and found to work. Data concerning material and laboratory equipment have been collected and are now available.

By using a quantitative procedure forthe determination of the small amounts of endotoxin present in most samples, it has been possible to find optimal reaction conditions and to trace various kindsof errors. Procedures for method controland trouble shooting are also suggested.