Quantitative structure activity relationships (QSARs) relate chemical structure with a measurable physical or chemical characteristic, such as hydrophobicity, electrophilicity or toxicity, or a combination of these factors. This can be done either by trend analysis or data gap filling depending on the type of data and number of data available.
It is important that any QSAR data has been validated and details are provided on how the QSAR was validated. To see more details related to validations see below.
If submitting QSAR data it is important to fill in the QSAR reporting form (Word, 20 KB or PDF, 83 KB). This form is based on the ECHA QSAR reporting form and has been amended to contain important instructions that make filling in the form easier, however full instructions on how to fill in the form are provided in the ECHA guidance document "Guidance on information requirements and chemical safety assessment Chapter R.6: QSARs and grouping of chemicals". In some cases such as OECD Toolbox and VEGA the report will be in IUCLID 5 or 6 format which follows the QSAR reporting form layout. Note in many cases these platforms allow free text to be entered into the report and this allows the chemical supplier who has carried out the modelling to add annotation detailing why a particular group of chemicals or species were discarded as part of data trimming. If ‘free text boxes’ do not exist this information should be provided as supplementary information as a word or pdf document.
Data should not be trimmed without explanation. It is important that annotation is made in order that Cefas understands the process that has been used to achieve the outcome.
Appropriate data should be used. If the QSAR outcome is to determine toxicity to fish it is important that only fish data is used, similarly with algae and invertebrate data. It is also important that the appropriate test is used.
It is important that the limitations of QSAR modelling are understood and taken into consideration the chemical type or family.
QSARs are models which answer a specific question based on the physico-chemical properties of a target chemical based on its structure.
Not all algorithms or models are suitable for all chemicals, an example of this would be the use of QSAR data to describe toxicity in UVCB chemicals or surface active chemicals (surfactants).
The data that is used in the QSAR model must be of good quality and be rated at least Klimisch 1 or 2. Ideally the test information should be available as part of the QSAR platform you are using to determine whether the data related to the structural feature is sufficiently strong.