The development and establishment of a heat inactivated preparation of Mycobacterium tuberculosis (H37Rv) as the first international standard for nucleic acid amplification techniques

A need to develop an inactivated Mycobacterium tuberculosis (Mtb) preparation, to be used as a DNA standard, as an important and urgent requirement for Tuberculosis (TB) diagnostics standardization was identified in 2018. A candidate material was generated using a heat inactivated culture of Mtb strain H37Rv. A lyophilised preparation was evaluated for its suitability as an International Standard for molecular detection of Mtb DNA in an international collaborative study. Together with the use of quantitative PCR assays and rapid diagnostic tests, this candidate standard was demonstrated to be fit-for-purpose. Based on the results from this collaborative study, it is proposed this lyophilised heat inactivated Mtb preparation (NIBSC code: 20/152) to be established by the World Health Organization Expert Committee on Biological Standardization, as the First WHO International Standard for Mycobacterium tuberculosis (H37Rv) for nucleic acid amplification techniques with an assigned unitage of 6.3 log₁₀ or 2 × 10⁶ International Units per vial.

The intended uses of this IS are for calibration of secondary or in-house reference preparations used in the assays for the molecular detection of Mtb DNA. It may also be used for assay validation and monitoring the performance in terms of limit of detection of rapid diagnostic tests.