Nucleic Acid Extraction and Purity, Including Performance Considerations of Different Extraction Chemistries

Downstream molecular assays rely on highly specific extraction of nucleic acid inputs from clinical materials. The variety of downstream analytical assays from amplification-based detection to probe-based identification and next-generation sequencing approaches play a critical role in determining the extraction workflows implemented by clinical labs. Extraction that occurs solely through differential partitioning in liquids is referred to as liquid-phase extraction. In contrast, solid-phase extraction utilizes one of several exogenous matrices to selectively bind targeted nucleic acid, facilitating removal of impurities and concentration. Sample-to-answer technologies follow one of two design concepts, those designed for large-scale batched testing and those designed for smaller batch, random access sample-to-answer testing. Examples of large-scale batched assays include the cobas 6800/8800 (Roche), the Alinity m (Abbott), and the Panther Fusion System (Hologic). Extraction-free approaches perform testing on minimally processed specimens, without rigorous separation of nucleic acid from other sample materials.