IMDRF Revises Adverse Event Terminology for Medical Devices: What Thai FDA Vigilance Teams Must Update

On March 3, 2026, IMDRF published the 2026 release of IMDRF/AE WG/N43, the standard that defines the terminology and alphanumerical codes used for categorized adverse event reporting on medical devices and in vitro diagnostic devices. It is a technical document, easy to overlook, but it directly affects how device vigilance teams file with Thai FDA. A report submitted on time using outdated codes is still a deficient report, and that distinction matters more than most companies realize until it costs them a resubmission.

What Changed in the 2026 Release

N43 governs seven reporting categories: device problems, patient problems, clinical signs and symptoms, investigation findings, adverse event types, component codes, and evaluation codes. The 2026 release revises definitions and codes across all seven and supersedes every earlier version. It exists because adverse event data only becomes useful across borders when regulators are working from the same vocabulary; without shared codes, comparing safety signals between countries becomes guesswork rather than analysis. The most consequential changes in this release address device technology that earlier N43 versions simply did not anticipate. New device problem codes now capture software-related failures and AI/ML performance anomalies, and the patient problem and evaluation code taxonomies have been revised to reflect how clinical practice actually categorizes these events today. The updated standard is published directly by IMDRF: IMDRF N43, Terminologies for Categorized Adverse Event Reporting.

Why This Reaches Every Thai FDA Vigilance Filing

Thailand's post-market surveillance framework requires device license holders to report serious adverse events and malfunctions to Thai FDA within set timelines, and Thai FDA's incident reporting system is built around international standards including IMDRF terminology. A report filed using deprecated or non-standard codes risks outright rejection or a request for resubmission, and that delay in formal receipt can itself create a technical non-compliance problem even when the underlying incident was reported promptly and in good faith.

Companies with software as a medical device (SaMD) or AI-enabled portfolios have the most work to do here. The 2026 release's new device problem codes are specifically built to capture software failure modes, including algorithm performance drift and unintended output, that previous code sets simply had no field for. If your team has been approximating these events with legacy codes because nothing else fit, that workaround is no longer necessary and, going forward, no longer acceptable. IVD manufacturers and importers should look closely at the evaluation code and investigation findings revisions too, since these categories directly shape how a root cause analysis gets classified in the formal Thai FDA report. Any internal investigation template or quality management system module still built around an earlier N43 code set needs to be brought current before the next reportable event, not after one is already in motion.

Bringing Your Reporting Current

Start with a direct, line-by-line comparison between the 2026 N43 release and whatever code set your vigilance team is actually using today. The device problem, evaluation, and investigation findings categories carry the most substantive revisions, so concentrate the review there first, and keep a written change log as you go. That log is worth having on hand if Thai FDA or an internal audit ever asks why a report's coding shifted between filings.

Once the gaps are documented, update every internal reference to the old codes, including adverse event report forms, investigation templates, and any automated code-selection logic inside your vigilance software. Make these changes before your next reportable event rather than scrambling once one occurs. In Thailand, adverse event reports are typically prepared or reviewed by the local license holder or an in-country regulatory representative, and a mismatch between a manufacturer's internal report and what the local license holder actually files with Thai FDA is one of the more common, and entirely avoidable, causes of a resubmission request. Make sure whoever is preparing the Thai filing is working from the same 2026 code set as the rest of your organization.

Finally, if your reporting has relied on an earlier N43 version for any meaningful stretch of time, it is worth reviewing past submissions to Thai FDA for codes that this release has revised or eliminated outright. Where miscoding turns up, talk to your regulatory advisor before deciding whether a voluntary correction or resubmission is the right move. Getting ahead of it is a far better position than having Thai FDA identify the inconsistency first.

DeeMED Consulting supports device license holders in Thailand with post-market vigilance work, including aligning adverse event reporting to current IMDRF terminology before it becomes a Thai FDA compliance issue. If your team needs a review of its N43 alignment or help preparing an adverse event submission, our local license holder services cover exactly this kind of ongoing regulatory representation.