Exempt from 510(k). Restricted anyway.

An analyte specific reagent looks, on paper, like one of the easiest categories in the in vitro diagnostics world to get right: most of them never need a 510(k) at all. That is true, and it is the smaller half of the rule. The same regulation that exempts the reagent from premarket review also names exactly who it can be sold to, and the exemption itself carries two named exceptions most people skip past.

What an ASR actually is, and what 864.4020 exempts

21 CFR 864.4020 defines an analyte specific reagent: antibodies, both polyclonal and monoclonal, specific receptor proteins, ligands, nucleic acid sequences, and comparable reagents that identify or quantify a single analyte in a biological specimen through a specific binding or chemical reaction. An ASR is not itself a test; it is the component a laboratory builds a test around. The regulation classifies most ASRs as Class I and exempts that class from the premarket notification requirements of Part 807, subpart E, with two exceptions written into the same paragraph: a defined Class II subset, used in blood-banking tests that are themselves Class II, and a Class III subset reserved for the highest-risk analytes. Neither carve-out gets the Class I exemption at all.

Restricted regardless of class

The Class I exemption answers only the premarket-review question. It says nothing about who can buy the reagent. 21 CFR 809.30 answers that separately: an ASR is a restricted device under FD&C Act § 520(e), and the regulation names exactly who it may be sold to — in vitro diagnostic device manufacturers, laboratories qualified to perform high-complexity testing under CLIA, laboratories regulated by the Department of Veterans Affairs, and organizations using the reagent for a purpose other than providing diagnostic results to a patient or practitioner, such as forensic, academic, or other nonclinical research use. A sale to a buyer outside that list is a restricted-device violation even when the reagent itself never needed a 510(k) to reach the shelf.

The label has to say what the reagent can’t claim

21 CFR 809.10(e) sets the labeling that comes with the exemption: a Class I exempt ASR has to carry a disclaimer stating that its analytical and performance characteristics have not been established by FDA review. The reagent skipped that review because it isn’t a finished test; the label has to keep saying so.

The exemption covers the reagent FDA didn’t review. It was never written to cover who buys it, or what its label is allowed to promise.

The practice

A compliance check that stops at “is this ASR Class I” has confirmed one thing and skipped two others: whether the specific analyte actually falls inside the Class II or Class III carve-out in 864.4020’s own text, and whether every buyer on the distribution list actually qualifies under 809.30. Both checks run on facts specific to the reagent and the customer, and belong with the regulatory and quality professionals who own that file — this describes how the exemption and the restriction fit together, regulatory intelligence and method, never a determination about any specific product.

None of it shows up in a clearance search either way. Per what we monitor and how often, FDA Radar’s 510(k) feed has nothing to post for an exempt Class I ASR, because no review ran to generate a K-number — the classification database carries the regulation number and class, and that is the full extent of the public record for a reagent most of the IVD supply chain never has to clear at all.