title: Intralaboratory validation of cell-free translation assay for detecting ricin toxin biological activity.
abstract: A cell-free translation (CFT) assay for determining ricin biological activity was validated. The statistical data from the validation study showed a high level of precision within and between runs of the assay. The assay was specific for determining ricin biological activity in food-based matrixes and discriminated ricin from other ribosome-inactivating proteins. The mean bias (relative error) between measured ricin concentrations of 3 validation samples and their nominal concentrations was 1.1, 6.6, and 20.3%, while the coefficient of variation (CV) was 14.1, 7.7, and 13.5%, respectively, demonstrating good precision, accuracy, and linearity. The CVs of ricin concentrations in 2 ricin-containing samples calculated from a dilution series were <5 and <12%, respectively, demonstrating very good parallelism. The analyte stability of ricin-containing samples stored for 1 month either at 4 or -20 degrees C, the stability of ricin stock solutions, and the results of assays executed by different analysts and using different luminometers were evaluated. The statistical validation data confirmed that the 4-parameter logistic equation, y = (a - d)/[1 + (x/c)b] + d, provided an accurate representation of a sigmoidal relationship between the measured response and the observed ricin concentration for the CFT assay.
authors.affiliation: U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD 21702-5011, USA. changhong.lindsey@amedd.army.mil
authors.forename: Changhong Y
authors.initials: CY
authors.lastname: Lindsey
authors.forename: Jenny D
authors.initials: JD
authors.lastname: Richardson
authors.forename: J Edward
authors.initials: JE
authors.lastname: Brown
authors.forename: Martha L
authors.initials: ML
authors.lastname: Hale
mesh_terms: D001681:Biological Assay; D002138:Calibration; D002474:Cell-Free System; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D019411:Clinical Laboratory Techniques; D015233:Models, Statistical; D012044:Regression Analysis; D015203:Reproducibility of Results; D012276:Ricin / Q000032:analysis / Q000737:chemistry* / Q000633:toxicity; D012680:Sensitivity and Specificity; D013696:Temperature; D014118:Toxins, Biological / Q000032:analysis
chemical_list: D014118:Toxins, Biological; D012276:Ricin