WHO International Standards for tumour markers: Development, characterisation and future perspectives.

BackgroundMeasurement of the circulating protein-based tumour markers by immunoassay is used in the routine clinical care of cancer patients, from aiding diagnosis to monitoring disease progression, response to therapy and detecting recurrence. The standardisation of these immunoassays is of critical importance, where inter-method variability and a lack of harmonisation can impact the comparability of results and affect clinical utility. World Health Organisation (WHO) International Standards (IS) are available for many of these protein tumour markers.ObjectiveTo provide an overview of how these WHO IS are prepared, characterised and established, and introduce the IS that are available for the calibration of tumour marker immunoassays.Results and conclusionAlthough WHO IS are available for many protein tumour markers, there remains a need for improvement in the harmonisation of some of these assays to enable more widespread and optimum utilisation in clinical practice. It will remain important to maintain these WHO International Standards, to achieve harmonisation through consistent global calibration of these assays, in addition to supporting the development of new technologies as they arise.