Standards Development

Scope

This document specifies the derivation of biological equivalence (BEQ) concentrations for results of in vitro bioassays which are based on measuring effects on a biological process such as enzyme induction or cellular growth. The concept described here can be used for any biological assay after the proof of its applicability.

To derive BEQ concentrations, the effect on a biological process caused by a sample – i.e. the activity of the sample – is expressed in terms of a concentration of a reference compound which results in an equivalent effect on the process. The term "sample" used in this document addresses environmental samples as well as defined mixtures and pure compounds used as test item in a bioassay. BEQ concentrations can be derived for environmental water samples, extracts of environmental water samples including tap water or solutions of pure chemicals or mixtures of chemicals.

Purpose

The concept of biological equivalence concentrations (BEQ) – described in ISO 23196:2022 – is used to express a biological activity measured by a biological test in terms of a concentration of a defined reference compound. The use of BEQs is implemented in the COMMISSION REGULATION (EU) No 589/2014 (2 June 2014) - Bioassay as screening tool (Dioxins + PCB in food). Furthermore, the BEQ-concept is included in parts 1 to 3 of ISO 19040 :2018, describing methods for the detection of agonistic effects on the estrogen receptor. It is to be expected that the concept will be more widely used in regulatory frameworks in the near future in which effect based trigger values are implemented. This NWIP describes a robust way to calculate BEQs based on concentration effect relationship of samples and reference compounds using the PCx approach outlined in OECD 455. It provides instructions how to assess the quality of the experimental data and further quality measurements for the fitting of the underlying data. Requirements for reporting of meta-data for a correct interpretation of the BEQ are defined.