CCQM-K61: Quantitation of a linearised plasmid DNA, based on a matched standard in a matrix of non-target DNA

Abstract

Key comparison CCQM-K61 was performed to demonstrate and document the capability of interested National Metrology Institutes in the determination of the quantity of specific DNA target in an aqueous solution. The study provides support for the following measurement claim: "Quantitation of a linearised plasmid DNA, based on a matched standard in a matrix of non-target DNA". The comparison was an activity of the Bioanalysis Working Group (BAWG) of the Comité Consultatif pour la Quantité de Matière and was coordinated by NIST (Gaithersburg, USA) and LGC (Teddington, UK). The following laboratories (in alphabetical order) participated in this key comparison. DMSC (Thailand); IRMM (European Union); KRISS (Republic of Korea); LGC (UK); NIM (China); NIST (USA); NMIA (Australia); NMIJ (Japan); VNIIM (Russian Federation) Good agreement was observed between the reported results of all 9 of the participants. Uncertainty estimates did not account fully for the dispersion of results even after allowance for possible inhomogeneity in calibration materials. Preliminary studies suggest that the effects of fluorescence threshold setting might contribute to the excess dispersion, and further study of this topic is suggested.

An outlier-resistant indicator of anomalies among inter-laboratory comparison data with associated uncertainty

“…In particular, any symmetric distribution with shape and dispersion invariant to location could be treated by the simulation method suggested above. It is less clear how other distributions (for example, lognormal, beta-binomial or Poisson) could be handled with any generality, especially when different participants report uncertainty information using different distribution families (for example, study CCQM-K61 includes intervals from both normal and lognormal distrubutions [26]). Such cases are problematic for any method reliant on simulation with a common assumed mean, as a shift in (true) mean implies a concomitant change in shape and scale.…”