--- title: "Lost to Follow-up, Definition | MedTech Terms" description: "Subjects whose outcome data are missing because they did not complete planned visits. Plain-English Clinical & Trials definition for MedTech teams, with example" lang: en json-ld: | { "@context": "https://schema.org", "@graph": [ { "@type": "DefinedTerm", "@id": "https://medtechterms.com/terms/lost-to-followup#term", "name": "Lost to Follow-up", "description": "Loss to follow-up reduces power, biases estimates if non-random, and is a leading reason for clinical-trial credibility concerns. 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These methods should be pre-specified in the statistical analysis plan." } }, { "@type": "Question", "name": "Are there specific requirements for reporting lost to follow-up?", "acceptedAnswer": { "@type": "Answer", "text": "While there isn't a single universal regulation solely on LTFU reporting, guidelines like ICH E9 (R1) expect comprehensive reporting of all withdrawals and losses to follow-up, along with their reasons, to enable a transparent assessment of the study's integrity and generalizability." } } ] } ] } --- [ MedTech Terms The authoritative reference ](/) Browse Learn [Latest](/latest) About 1. [Home](/) 2. / 3. [Terms](/terms) 4. / 5. [Clinical & Trials](/terms?cat=Clinical%20%26%20Trials) 6. / 7. Lost to Follow-up [All terms](/terms) Clinical & Trials [Clinical Evidence](/ecosystems/clinical-evidence) # Lost to Follow-up Subjects whose outcome data are missing because they did not complete planned visits. Reviewed by [Christian Espinosa, Founder, Blue Goat Cyber](/authors/christian-espinosa) Last reviewed May 5, 2026 ## Definition Loss to follow-up reduces power, biases estimates if non-random, and is a leading reason for clinical-trial credibility concerns. Sponsors should pre-specify thresholds, sensitivity analyses, and retention strategies. What the regulation says Regulators emphasize the importance of minimizing lost to follow-up (LTFU) in clinical trials, as outlined in documents like the FDA's guidance on "E10 Clinical Development for Drugs Attenuating Progressive Neurodegenerative Diseases" which discusses trial integrity. They expect sponsors to implement robust strategies to maximize participant retention and to transparently report on LTFU rates and their potential impact on study results, as described in ICH E9 (R1) statistical principles for clinical trials. The EU [MDR](/terms/mdr-reporting) also implicitly requires adequate follow-up in [post-market clinical follow-up](/terms/pmcf) (PMCF) studies to ensure continued safety and performance assessment of Medical Devices. ## What this means in practice Long-term implant studies and [digital therapeutic](/terms/samd-dtx) trials are particularly prone to LTFU; remote follow-up models can mitigate but introduce data-quality questions. ## Examples - A sponsor of a long-term orthopedic implant study develops a detailed patient retention plan, including regular communication, travel assistance, and flexible follow-up options, to minimize lost to follow-up over a 10-year period. - During a clinical trial for a novel digital therapeutic, the sponsor conducts an interim analysis and discovers a higher-than-expected lost to follow-up rate, prompting an immediate review and adjustment of patient engagement strategies. - A post-market clinical follow-up (PMCF) study for a cardiovascular device accounts for potential lost to follow-up by over-enrolling participants, ensuring sufficient data remain for robust analysis even with anticipated attrition. Common pitfalls - • Failing to document and justify the chosen LTFU thresholds can lead to regulatory scrutiny. - • Assuming LTFU is always missing completely at random (MCAR) without conducting appropriate sensitivity analyses is a common statistical error. - • Not having a pre-specified plan for handling missing data due to LTFU can result in biased study conclusions. - • Overlooking the impact of LTFU on the statistical power of the study can lead to underpowered trials. - • Neglecting to implement specific retention strategies tailored to the study population and device type increases the risk of high LTFU rates. ## Frequently asked questions What is the primary regulatory concern regarding lost to follow-up? The primary regulatory concern is the potential for LTFU to introduce bias into study results, compromise the statistical power of a trial, and ultimately affect the reliability and validity of evidence supporting a Medical Device's safety and effectiveness. How should sponsors address potential bias from lost to follow-up? Are there specific requirements for reporting lost to follow-up? ## Related terms Grouped by theme ### Editor's picks · Hand-selected related concepts [ Clinical & Trials Intent-to-Treat vs Per-Protocol(ITT / PP) Two analysis populations: ITT analyzes everyone randomized; PP analyzes only those compliant with protocol. ](/terms/itt-pp)[ Clinical & Trials Protocol Deviation Departure from the approved clinical investigation plan. ](/terms/protocol-deviation) ### More in Clinical & Trials · Same category [ Clinical & Trials Adaptive Trial Design Trial design that pre-specifies opportunities to modify aspects (sample size, arms, endpoints) based on interim data. ](/terms/adaptive-trial)[ Clinical & Trials Adverse Event(AE) Any untoward medical occurrence in a subject, whether or not related to the device. ](/terms/adverse-event)[ Clinical & Trials ALCOA+ Data integrity principles: Attributable, Legible, Contemporaneous, Original, Accurate (plus Complete, Consistent, Enduring, Available). ](/terms/alcoa-plus)[ Clinical & Trials Analytical Sensitivity An IVD's ability to detect small quantities of an analyte. ](/terms/analytical-sensitivity) Cited by Where this term appears across MedTech Terms. Ecosystems (1) - [Clinical Evidence](/ecosystems/clinical-evidence) ## Primary references 3 sources Link health: 3 verified · last checked 2026-06-20 ICH· 2 ISO· 1 1. [1 ICH E9(R1) Verified ICH · ich.org ](https://www.ich.org/) 2. [2 ICH Guidelines Verified ICH · ich.org ](https://www.ich.org/page/ich-guidelines) 3. [3 ISO 14155 Standard Page Verified ISO · iso.org ](https://www.iso.org/standard/71690.html) Inline markers like \[1\] jump to the matching reference above. Sponsor note ### Clinical evidence intersecting with device security? We support clinical-stage MedTech teams whose investigational devices touch patient data or hospital networks. [Book a 30-minute discovery session](https://go.bluegoatcyber.com/meetings/blue-goat-cyber/discovery-session) - No obligation - Expert-led from minute one - NDA available on request MedTech Terms is a community resource sponsored by [Blue Goat Cyber](https://bluegoatcyber.com). Definitions are independent of any vendor. On this term Category Clinical & Trials Sources 3 Updated 5/5/2026 [Compare with another term](/compare?a=lost-to-followup) Learn in 60 seconds Card Lesson Quiz Subjects whose outcome data are missing because they did not complete planned visits. - · Long-term implant studies and digital therapeutic trials are particularly prone to LTFU; remote follow-up models can mitigate but introduce data-quality questions. - · Sponsors should pre-specify thresholds, sensitivity analyses, and retention strategies. Remember this Watch out: Failing to document and justify the chosen LTFU thresholds can lead to regulatory scrutiny. Related terms - [Intent-to-Treat vs Per-Protocol(ITT / PP) ](/terms/itt-pp) - [Protocol Deviation ](/terms/protocol-deviation) You may also need Auto-suggested from Clinical & Trials and shared keywords. - [Sample Size and Statistical Power ](/terms/sample-size-power) - [ICH E6 Good Clinical Practice(GCP) ](/terms/ich-gcp) - [ALCOA+ ](/terms/alcoa-plus) - [Clinical Evaluation Report(CER) ](/terms/cer) - [Decentralized Clinical Trial(DCT) ](/terms/decentralized-clinical-trial) - [Feasibility Study ](/terms/feasibility-study) [All Clinical & Trials terms](/terms?cat=Clinical%20%26%20Trials) From the Blue Goat network Related resources and services on this topic. - [ MedTech Launchpad MedTech funding rounds, accelerators, and launch resources. ](https://medtechlaunchguide.com) MedTech Terms An authoritative, plain-language reference for the regulatory, quality, cybersecurity, and software terms that shape modern medical devices. 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