ABSTRACT
Sample selection is the initial stage of a process whereby data on the characteristics of a batch are collected for evaluation. By definition, only a fraction of the batch is sampled for testing; clearly, therefore, that fraction must be representative of the batch in question. Since the fate of the batch depends upon the results generated from that first sample, sample selection must be regarded as a critical process and an essential part of the quality assurance system. As with any sampling process, appropriate predetermined indicators of quality, known as attributes, must be identified which reflect the characteristics of the batch; these are assumed not only to be homogeneously distributed throughout the batch but also to be recovered during a random sampling scheme. In microbiological sampling, however, these characteristics may not necessarily be randomly distributed throughout the batch and the sampling scheme should therefore reflect this. Sampling schemes currently employed in the pharmaceutical industry are increasingly based on an analysis of vulnerable points in a system, otherwise known as hazard analysis and control of critical points (HACCP), as discussed in more detail below.
