EU MDR Trend Reporting under Article 88: Thresholds and Denominators

1. Key takeaways

Under Article 88 of the MDR, manufacturers must, through the electronic system referred to in Article 92, report to the competent authorities concerned cases where the frequency or severity of non-serious incidents shows a statistically significant increase, or where expected undesirable side-effects show a statistically significant increase, provided that the increase could have a significant impact on the benefit-risk analysis and has led or may lead to unacceptable risks. The trigger is statistical, not anecdotal, which makes the quality of the underlying PMS data decisive.

Because the obligation depends on rates rather than single events, companies need predefined baselines, monitoring frequency and statistical thresholds written into the PMS plan. Without those, the duty under Article 88 cannot be performed in a demonstrable way, and regulators will treat the absence of thresholds as the absence of compliance.

Article 88 changes the compliance question from whether an individual event reached the serious threshold to whether the pattern of ordinary events has shifted. That shift in perspective requires tools many companies have never built: baseline rates per event category, a defined monitoring interval, a statistical test agreed in advance and a decision record for every review. Building them is a one-time project; running them is a monthly routine. The companies that struggle with Article 88 are almost never those with poor statistics, but those that never wrote the methodology down.

2. Legal basis

The trend reporting duty is anchored in Article 88 of Regulation (EU) 2017/745 and interacts with the PMS and vigilance provisions listed below.

3. Expert insights

Insight 1: Trend reporting fills the regulatory gap below the serious incident threshold.

Article 87 covers only serious incidents. Events that do not reach the threshold of Article 2(65) must nevertheless be reported under Article 88 once a statistically significant increase has formed. This duty is frequently overlooked because companies internally configure only one gate, namely the serious incident assessment, and assume that events which fail that gate need no regulatory follow-up at all. A single gate design leaves the entire category of accumulating non-serious events unmonitored, which is precisely the situation Article 88 was written to close.

Insight 2: The reporting trigger depends on predefined baseline rates and statistical thresholds.

Annex III requires the PMS plan to specify the methods used to detect statistically significant increases of the kind described in Article 88. The phrase statistically significant is a relative concept: without predefined baseline rates and trigger thresholds, no increase can be determined to be significant, and the reporting obligation cannot be discharged. Thresholds must therefore be written into the PMS plan in advance, rather than determined subjectively after the data accumulate (a practical estimate). Where thresholds are missing, the practical answer is not to report nothing but to define the methodology first and apply it to the accumulated data. A workable pattern is to define, per event category, a baseline rate from a reference period, a minimum observation volume below which no judgement is made, and a trigger rule expressed in simple statistical terms. The methodology, once written, should be reviewed at fixed intervals and its version history kept with the PMS plan.

Insight 3: The denominator is a necessary condition for any trend judgement.

Judging whether an incidence rate has risen requires knowing the denominator. The PMS plan must therefore collect sales volumes, installation counts or usage frequency alongside incident counts; otherwise growth in the number of complaints cannot be distinguished from growth in sales (a practical estimate). A dashboard that displays only complaint counts is structurally incapable of supporting the Article 88 duty, no matter how well the complaints themselves are documented.

Insight 4: Articles 88 and 87 are two parallel channels.

A single set of events can trigger both obligations simultaneously: individual events that meet the serious incident threshold go through Article 87, with the 15-day, 10-day or 2-day deadlines, while the overall trend of events that do not reach that threshold goes through Article 88. The two channels differ in reporting target and in content, and they cannot substitute for each other. Process design must keep them separate so that one reporting track does not crowd out the other during peak event volumes. In practice the two channels also differ in form: the serious incident channel works through individual case reports with fixed deadlines, while the trend channel works through aggregated analyses submitted when a threshold is crossed. Giving ownership of both to one team is acceptable; merging their documentation is not.

4. Practical recommendations

The measures below concentrate on methodology and monitoring, because those are the elements regulators ask for first when a trend report, or its absence, is examined.

1. Define baseline rates, monitoring frequency and statistical trigger thresholds in advance for each event category, inside the PMS plan.
2. Operate a monthly or quarterly rate dashboard that always shows incident counts together with their denominators.
3. Design the trend reporting path separately from the serious incident reporting path under Article 87, so that the two do not compete for the same resources.
4. Retain the decision records and reasoning for every determination that an increase was not statistically significant, for audit sampling.
5. Review thresholds periodically: recalibrate after changes in the sales mix or in the population of users (a practical estimate).

5. Verification checklist

Use the checklist below to confirm that trend detection is designed, operated and documented as a standing process.

• □ The PMS plan contains trend detection methods and statistical thresholds
• □ A rate dashboard is in place (incident counts plus denominators)
• □ The trend reporting flow is separated from the Article 87 serious incident flow
• □ Decisions of not statistically significant are documented and archived
• □ Thresholds are reviewed and recalibrated at defined intervals
• □ The submission path through the Article 92 electronic system has been confirmed

Regulatory information verified as of 29 October 2026.

GRZAN regulatory support. GRZAN assists medical device manufacturers with post-market compliance in the European Union market under Regulation (EU) 2017/745, covering vigilance and trend reporting, field safety corrective action (FSCA) recalls, and responses to competent authority inspections. If you need support with your EU MDR post-market obligations, contact info@grzanglobal.com.