WHO International Standards and Reference Panels

These reagents are produced under the WHO Biological Standardisation programme and are intended for the calibration of secondary reference materials and in the validation of NAT-based assays. They are not intended for routine use. The concentration of each reagent is assigned in International Units (IU). This is an arbitrary value, established by consensus following extensive international studies involving many laboratories. The supply of WHO International Standards is limited to five vials per laboratory per year in order to preserve stocks. The supply of WHO International Reference Panels is limited to two panels per laboratory per year. Specific information on the reagents listed below can be sourced via the product code hyperlink and the WHO report. For any further information please contact enquiries.

Reference materials in development

Proposed replacement reference preparation:

Proposed new reference preparation:

Frequently asked questions

Q: What is the conversion factor between IU and copies?

A: There is no precise conversion factor to any International Standard that has been assigned an International Unit by the WHO as the number of copies, genome equivalents or PCR detectable units/ml is entirely dependent on the assay in which the laboratory uses. Any conversion factor will also change over time as assay sensitivity improves. The value of an International Standard is to give a fixed absolute unit which can be used to calibrate further working standards. Please refer to the appropriate PDF report (above) which was submitted to and accepted by the WHO Expert Committee on Biological Standardisation. This shows the different assay systems and associated mean values that were obtained in each study. Unfortunately, no firm conversion factor can be given, however, the information given in each report may act as a guide for the assay system that you are using.