The 21 CFR 809.10 and 21 CFR 864 define four types of IVDs: General Purpose Reagent (GPR), Investigational Use Only (IUO), Analyte Specific Reagent (ASR) and Research Use Only (RUO). This is why in the U.S., RUOs are also called RUO IVDs – In contrast, in EU, only the term RUO prevails.
As per the 21 CFR, RUO products are IVD products in the laboratory research phase of development and not represented as effective IVDs (21 CFR 809.10(c)(2)(i)). In essence, RUO products are reagents, instruments, or systems under development and evaluated for their potential use as IVDs (Evaluation of design, performance, usability, etc.).
RUO product are essentially unregulated in the U.S but must be labelled with the following statement: “For Research Use Only. Not for use in diagnostic procedures”. Labelling a product as such permits it to be used by researchers, who can evaluate usefulness for a specific diagnostic purpose. Beyond the labelling statement, FDA regulations do not mandate any other restrictions or limitations on RUO products, and RUO manufacturers do not have to register or list their RUO products with FDA or comply with manufacturing standards. RUO products can be offered for sale without any FDA clearance or approval.
RUO products can be also used in conducting nonclinical laboratory research with goals other than commercial IVD product development and are used in basic life science research and not intended for further clinical diagnostic use development. In this case, these RUOs are used to carry out research and are not, themselves, the object of the research.
As good marketing practices, RUO products must never be represented as effective IVD products. And no specific disease, condition, or diagnostic performance claims can be made for RUO products. In the other side, an IVD product that is inappropriately labelled as RUO may be also considered misbranded or adulterated due to the lack of premarket notification (510(k)) or premarket approval (PMA) if distributed/or labelled for clinical diagnostic purpose.
For more information, the FDA has published a guidance regarding IVD products labelled for Research Use Only. See section Recommended Reading.