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# Estimate Device Malfunction Risk Carefully: Attorney
- URL: https://www.fdaweb.com/estimate-device-malfunction-risk-carefully-attorney/
- Published: 2022-04-12T12:00:00.000Z
- Updated: 2026-09-14T17:40:17.000Z
- Author: David McFarland
- Tags: Devices, #legacy-id-D5151572

Attorney **Jeffrey Shapiro** (Hyman, Phelps & McNamara) says a 12/2021 FDA Warning Letter to Medtronic “provides an important reminder from FDA as to the correct estimation of risk associated with \[medical device\] malfunctions.” Writing in his firm’s *FDA Law Blog*, Shapiro [says](https://www.thefdalawblog.com/2022/04/estimating-risk-associated-with-medical-device-malfunctions-fdas-warning-letter-to-medtronic-highlights-an-under-appreciated-potential-source-of-error-in-the-estimation/?utm%5Fsource=rss&utm%5Fmedium=rss&utm%5Fcampaign=estimating-risk-associated-with-medical-device-malfunctions-fdas-warning-letter-to-medtronic-highlights-an-under-appreciated-potential-source-of-error-in-the-estimation) that among other issues, the letter faulted Medtronic for the way it calculated the risk of damaged retainer rings in its MiniMed 600 series insulin infusion pumps.

The agency criticized the risk calculation formula because it used the total shipment of affected products, which FDA said underestimated the probability of occurrence because the number of products shipped includes devices not in use by patients, such as those sent to distributors that have not yet been distributed to customers.

Shapiro says that while it is fairly common for companies to use shipment or sales figures as a denominator in a risk estimate, it seems that FDA is correct in this instance. “As FDA noted toward the end of the Warning Letter,” Shapiro concludes, “there was such a large gap between the number shipped versus the number in use (according to Medtronic’s own calculation) that the number held by distributors might not account for the entire gap. Whether true or not in that case, the lesson here is that an estimate of the delay in reaching the patient should consider all possible contributing factors and not simply time in possession of distributors. For instance, some products could remain in boxes in hospital inventory for an extended period. In a nutshell, when estimating risk of harm from a malfunction, be sure to consider whether the total shipments of affected products is an adequate proxy for the total number in use.”