The polymerase chain reaction (PCR) has proved to be a powerful and versatile tool and has opened new avenues in molecular biol­ ogy. Alternative nucleic acid amplification techniques, such as the ligase chain reaction (LCR), nucleic acid sequence-based amplifica­ tion (NASBA), and transcription-mediated amplification (TMA), a variation of NASBA, are also now available. These techniques are all designed to amplify specific nucleic acid sequences in an expo­ nential manner, thus providing a basis for extremely sensitive diag­ nostic assays. However, despite the widespread and successful ap­ plication of genomic amplification techniques in biological research, they have not yet reached the point of routine use in clini­ cal laboratories. Thus, although the R&D investment in nucleic acid diagnostics is in excess of $250 million annually, clinical ap­ plications remain relatively modest. One of the principal reasons for this delay in clinical application has been the problem of acci­ dental contamination of negative clinical specimens with minute amounts of amplified products from a previous positive reaction. Carry-over contamination of amplicons can now be prevented by chemical means or the use of a closed reaction system. However, the current instrumentation is essentially modular in nature, com­ prising machines that perform the three essential steps of nucleic acid amplification technology: sample preparation, the amplifica­ tion reaction, and detection of products. Consequently, the test pro­ cedures are more complicated with somewhat lower sample throughput than the enzyme immunoassays currently performed in clinical laboratories.

1 Evolution of Diagnostic Technologies.- 2 Enzymes Used in Nucleic Acid Amplification.- 3 Peptide Nucleic Acid.- 4 Sample Preparation for Nucleic Acid Amplification.- 5 Ligation-Based Nucleic Acid Probe Methods.- 6 PCR and Its Modifications for the Detection of Infectious Diseases.- 7 Qß Replicase Assays for the Clinical Detection of Infectious Agents.- 8 Application of Transcription-Mediated Amplification to Detection of Nucleic Acids from Clinically Relevant Organisms.- 9 Strategies to Avoid Amplicon Contamination.- 10 Labels and Detection Formats in Amplification Assays.- 11 Automation and Use of Robotics in Nucleic Acid Amplification Assays.- 12 Evaluation of Diagnostic Tests-Special Problems Introduced by DNA Amplification Procedures.- 13 Amplification Methods for Detection of Food-Borne Pathogens.- 14 Nucleic Acid Amplification Techniques in Detection and Diagnosis of Medically Important Viral Infections.- 15 Nucleic Acid Amplification Assays for Sexually Transmitted Diseases.- 16 Amplification for Detection of Mutations Imparting Drug Resistance in Mycobacteria.- 17 Cyclic Reactions for the Synthesis of Artificial DNA.- 18 Nucleic Acid Amplification Strategies for Diagnosis of Heritable Diseases.