Glossary
Last patient in (LPI)
The milestone when the final participant enrolls and enrollment closes. The gap between planned and actual last patient in is a direct measure of recruitment.
What does Last patient in (LPI) mean in clinical research?
Last patient in (LPI), also called last subject in, is the enrollment of the final participant in a trial; the CDISC Glossary defines it as the last subject enrolled in a clinical trial.[1] LPI closes the enrollment period and starts the countdown to the last visit, database lock and results. For ClinicalTrials.gov, the registered enrollment must be updated from the target number to the actual number once the trial reaches its primary completion date.[2]
Missed LPI dates are common. A 2018 review cited a study of 114 UK trials in which only 31% met their enrollment goals, and another in which one-third of publicly funded trials required a time extension because they failed to meet initial recruitment goals.[3] Each extension keeps sites, monitors and vendors running longer and delays the data.
Practical note: a late LPI is usually visible months ahead in the per-site enrollment rate. Forecast LPI from the current rate, not the planned one, and add sites or outreach capacity early rather than in the final quarter. Engage handles first contact and scheduling so coordinators can spend their time on visits.
Sources
- 1.NCI Thesaurus C142597: Last Subject In Identity (CDISC Glossary) · National Cancer Institute EVS / CDISC, 2026Quote: "The last subject enrolled in a clinical trial."
- 2.42 CFR 11.10 Definitions (Clinical Trials Registration and Results Information Submission) · eCFR (NIH/NLM), 2026Quote, 11.10(b)(18): "Once the trial has reached the primary completion date, the responsible party must update the Enrollment data element to reflect the actual number of human subjects enrolled in the clinical trial."
- 3.Factors associated with clinical trials that fail and opportunities for improving the likelihood of success: A review · Contemporary Clinical Trials Communications, via PMC, 2018Quote: "In addition, Campbell et al. reported that one-third of publicly funded trials required a time extension because they failed to meet initial recruitment goals."