Interlaboratory Performance Study of Cyanobacteria <scp>DNA</scp> Reference Materials Using a <scp>qPCR</scp> Format for Monitoring Cyanobacterial Blooms

ABSTRACT Digital PCR (dPCR) has increasingly been used as a primary measurement method for the characterization of nucleic acid reference materials. Nucleic acid reference materials are particularly useful when used for the validation and calibration of quantitative PCR (qPCR). In this study, we describe the development and characterization of Cyanobacteria DNA reference materials (RM) using dPCR. An international interlaboratory study involving 14 laboratories was conducted using the Cyanobacteria DNA RM in combination with a lyophilized PCR reagent designed for the monitoring of Cyanobacteria bloom events. Of the 55 scored study results obtained using qPCR‐based techniques, 62% were within the 8% relative expanded uncertainty based on dPCR measurements, while 100% of the study results returned satisfactory z scores calculated using a set performance coefficient of variation equivalent to one Ct value. The study participants' results indicate that the cyanobacteria DNA RM is fit for the purpose of method validation and quality control of the qPCR format used for monitoring toxic cyanobacteria algae bloom events. Most importantly, the study results demonstrated that the use of standardized reagents combined with highly characterized nucleic acid RMs allows qPCR‐based DNA quantification technology to reach levels of accuracy and reproducibility comparable to those achieved with digital PCR technology.