A missed MDR is misbranding, not a defect

A CDRH warning letter routinely reaches for two words in the same document, adulterated and misbranded, and a fast read treats both as shorthand for “bad.” They are not the same finding. One names something wrong with the device or how it was made. The other names something FDA was owed and wasn’t given. Which word sits over which paragraph tells you what actually has to change before you read a single word of the narrative underneath it.

Adulterated is the statute for the device and its making

Section 501 of the FD&C Act — 21 U.S.C. § 351 — is where a device becomes adulterated. Two grounds do most of the work in device warning letters. Under 501(h), a device is adulterated when the methods, facilities, or controls used in its manufacture, packing, storage, or installation don’t conform to the Quality System requirements FDA has written into 21 CFR Part 820. Under 501(f)(1)(B), a device is adulterated when it needed premarket approval or an investigational device exemption and didn’t have one. Both grounds point at the same thing: the product, or the process that built it, is what the citation says fell short.

Misbranded is the statute for what FDA wasn’t told

Section 502 — 21 U.S.C. § 352— is where a device becomes misbranded, and the ground that surprises people is 502(t)(2): a device is misbranded when a firm fails or refuses to furnish material or information required under Section 519 of the Act and its implementing rules at 21 CFR Part 803 (Medical Device Reporting) and Part 806 (reports of corrections and removals). A firm that builds a conforming device on a compliant line, and then never files the thirty-day report a malfunction required, is not cited for a defective product. Nothing about the device itself is at issue. The citation is misbranding, because the thing that went missing was information owed to FDA, not conformance in the device. 502(o) runs the same way for a firm that skips registration, listing, or the premarket notice a 510(k) requires — a paperwork failure, cited as misbranding, on a device that may never have a flaw alleged against it at all.

A warning letter can allege a device is fine and still find a statute to cite. That statute is 502, not 501 — and the letter says so before it says anything else.

Why the label is worth reading before the narrative

The two grounds don’t just differ in name; they point at different remediation. A 501(h) finding is usually a CAPA and design-control problem, worked through the quality system a reinspection will eventually test. A 502(t)(2) finding can close on a procedural fix — a rewritten MDR procedure, retrained staff, a backlog of reports actually filed — without a single manufacturing process changing at all. A firm scanning a letter for how much work sits ahead of it learns more from which statute is cited, paragraph by paragraph, than from the violation count at the top.

The practice

Read a device warning letter’s citations before its narrative, and sort each one: 501 means the device or the line that built it, 502 means information FDA was owed and didn’t get. The sort is fast and it is a genuinely different signal than the paragraph count. Per what we monitor and how often, this is regulatory intelligence and method for reading a public warning letter, never regulatory advice about what a specific firm’s citations require it to fix — that determination belongs with counsel and the firm’s own regulatory team, working the letter directly.