Estimation of the POD Function and the LOD of a Qualitative Microbiological Measurement Method

Abstract

Abstract Qualitative microbiological measurement methods in which the measurement results are either 0 (microorganism not detected) or 1 (microorganism detected) are discussed. The performance of such a measurement method is described by its probability of detection as a function of the contamination (CFU/g or CFU/mL) of the test material, or by the LODp, i.e., the contamination that is detected (measurement result 1) with a specified probability p. A complementary loglog model was used to statistically estimate these performance characteristics. An intralaboratory experiment for the detection of Listeria monocytogenes in various food matrixes illustrates the method. The estimate of LOD50 is compared with the Spearman-Kaerber method.