When more really means more: WGS standards and quality control Next-generation sequencing (NGS) is reshaping the landscape of modern genetic diagnostic laboratories and their operational standards. NGS is gradually replacing the single-gene Sanger sequencing with targeted multigene panel-based resequencing for genes with variants implicated in any number of common diseases, from cardiovascular or neurological disorders to cancers or drug treatment response. Further advances in technology are positioning whole exome and ultimately whole genome sequencing (WES and WGS) for common diagnostic use. In a rapidly changing environment, quality control considerations are crucial. In this issue, Stephan White et al. (Hum Mutat 38: 912-921, 2017) discuss the critical steps that are required to properly perform WGS. They emphasize the key differences between WGS and WES, the important variables that need to be taken into serious consideration when performing NGS for both germline and somatic variants, the necessary quality control measures to monitor the entire process, and the standard operation procedures to ensure that NGS services will always be provided in a standardized manner. It is obvious that further technological advances in massively parallel DNA sequencing technology, accompanied by concomitant price reductions, will make WES and WGS more affordable and hence easier to become the ultimate genetic test in molecular diagnosis. Such advances must undoubtedly be accompanied with the necessary health technology assessment and economic evaluation analyses, demonstrating that such approaches are indeed cost-effective so that they can be adopted sooner and, most importantly, are covered by national healthcare systems. The points discussed in White et al., combined with those from recently published guidelines for variant calling, genomic databases, genomic data sharing and translational tools, should facilitate implementation of NGS services into the molecular diagnostic setting for routine clinical care.

Herbicide exposure may be an effect modifier of the relation between glutathione S-transferase pi gene polymorphisms and onset age in familial PD.