The focus on molecular methods for respiratory pathogen detection yielded a large variety of potential technologies for consideration in PERCH (Table 1) . Polymerase chain reaction (PCR) technology is more common at research sites worldwide, can be adapted to various platforms, and easily allows for multiplex amplification. Multiplexing, in which several targets are assayed for simultaneously, is commonly employed in PCR-based assays and offers significant advantages over single-pathogen assays in terms of efficiency and pathogen coverage. Still, developers must overcome considerable complexities in harmonizing the reaction requirements of each individual target and limiting potential competition among the analytes. These factors may result in a measurable decrease in sensitivity compared with single-plex assays. Several techniques have been developed to address such factors, such as alterations in cycling protocols [8] , nested primer combinations [9, 10] , complex primer structures and concentrations [11, 12] , and the use of nontraditional nucleotides [13] [14] [15] . Other NADT technologies, such as nucleic acid sequence-based amplification and loop-mediated isothermal amplification, have been used for the detection of respiratory pathogens, but experience with multiplexing is limited [16] [17] [18] [19] .