Characterisation of artefacts and drop-in events using STR-validator and single-cell analysis

•Characterisation of artefacts and drop-in contamination are demonstrated.•PCR of single-cells is proposed to infer the peak height distribution of drop-in.•Overlap in signal intensities between drop-in events and single-cells was observed.•Characterisation can improve existing models to interpret complex DNA results.

There is a need to understand the occurrence of drop-in and their peak height distributions to further improve existing models to interpret complex DNA results. The necessary data is usually very time-consuming to collect. Here we present a practical approach for simultaneous characterisation of reproducible artefacts and drop-in contamination from negative controls. As an alternative to the traditional approach we demonstrate the use of the DEPArray system as a source of single molecules for amplification to infer the peak height distribution of drop-in events. Though signal detection is often confounded by noise and artefact, single molecule contamination, or allele drop-in, is also regularly detected as demonstrated by the overlap in signal intensities between suspected drop-in events and signal obtained from single-cells.