نبذه عن الكتاب: Specificity and Performance of Diagnostic PCR Assays Konrad Sachse 1. Introduction The undisputed success of detection assays based on the polymerase chain reaction (PCR) has been largely due to its rapidity in comparison to many conventional diagnostic methods. For instance, detection and identification of mycobacteria, chlamydiae, mycoplasmas, brucellae, and other slow-growing bacteria can be accelerated from several days to a single working day when clinical samples are directly examined. Other microbial agents that are difficult to propagate outside their natural host often remain undetected by techniques relying on cultural enrichment, thus rendering PCR the only viable alternative to demonstrate their presence. Additionally, there is the enormous potential of DNA amplification assays with regard to sensitivity and specificity. Nowadays, when a new PCR assay is introduced into a laboratory, the diagnostician expects it to facilitate the examination of clinical samples without preenrichment and to allow specific differentiation between closely related species or subtypes at the same time. While there can be no doubt that the potential to fulfill these demanding criteria is actually inherent in PCR-based methods, and the present volume contains convincing evidence of this in Chapters 5–22, there is often a need for critical evaluation of a given methodology, not only in the case of obvious failure or underperformance, but also when certain parameters have to be optimized to further improve performance or reduce costs. The present chapter is designed to discuss the importance of key factors in PCR detection assays and provide an insight into basic mechanisms underlying the amplification of DNA templates from microbial sources. Besides the quality of the nucleic acid template (see Chapter 2) there are several other crucial parameters deciding over the performance of a detection method, e.g., the target region, primer sequences, and efficiency of amplification