Validation of an alternative method for counting Enterobacteriaceae in foods based on accuracy profile

Several years ago, microbiologists developed a harmonized standard for the validation of alternative methods against the reference method, namely International Organization for Standardization (ISO) 16140:2003. Since then a new and better statistical approach known as the accuracy profile concept has been proposed for interpretation of data collected during a validation study. This approach defines acceptability limits that are used to verify that an alternative analytical method can produce results acceptable for a defined analytical objective. This paper demonstrates how the accuracy profile approach can be efficiently applied to any data set collected according to ISO guidelines and how to interpret the final calculations to decide if a method is valid or not. The procedure was applied to data obtained in the validation of a commercial kit for the enumeration of Enterobacteriaceae in foods. A comparison of several statistical outputs derived from application of the accuracy profile demonstrated that this simple numerical method can be applied despite the non-normal distribution of bacterial colony counts.