A patient log is one of the most critical documents in clinical research. It is the real-time register of every participant you have enrolled, tracking their study journey from screening to final follow-up. For medical thesis work, maintaining a clean, accurate patient log can mean the difference between a well-defended study and a data integrity crisis at the viva.
This guide explains what a patient log must contain, how to structure it, and how to keep it updated without letting it become a burden.
What Is a Patient Log?
A patient log (also called a subject enrollment log or participant tracking sheet) is a running record that captures who has been enrolled in your study, when, and what has happened to them at each study visit. It is separate from your main data sheet — the log is about tracking; the data sheet is about variables.
What Your Patient Log Must Include
🆔 Identification Fields
Study ID, screening number, date of enrollment, and consent form number. Never record patient names in the main log.
📅 Visit Tracking
Date of each study visit, whether the visit occurred on schedule, and reason for any missed or delayed visit.
📊 Study Status
Current status for each patient: Enrolled, Active, Completed, Withdrawn, Lost to Follow-up, or Deceased.
📝 Withdrawal Notes
If a patient exits the study early, document the date and reason — adverse event, consent withdrawal, or protocol deviation.
Setting Up Your Patient Log: A Timeline Approach
Screening Phase
Assign a sequential screening number to every patient who is assessed for eligibility, even those who are not enrolled. Record why ineligible patients were excluded.
Enrollment
Once consent is obtained, assign a Study ID. Record the consent date and the name of the person who obtained consent.
Active Follow-up
Update the log after each study visit. Mark completed visits with a date and incomplete visits with a reason code.
Study Exit
Mark each patient as Completed, Withdrawn, or Lost to Follow-up with the relevant date. This determines your final evaluable sample.
Paper vs Digital Patient Logs
Paper logs have the advantage of being universally accepted and requiring no technical setup. However, they are prone to being lost, damaged, or illegible. If you use a paper log, photocopy or photograph it weekly as a backup.
Digital logs in Excel or dedicated platforms offer search and filter functions that make it easy to see, at a glance, which patients are due for a follow-up visit or which are missing data. A digital log also makes it simple to calculate your enrollment rate over time.
Common Patient Log Errors and How to Prevent Them
- Backdating entries — Always record events on the day they occur. Backdating is a serious data integrity violation.
- Using correction fluid (Tipp-Ex) — For paper logs, always cross out errors with a single line, initial, and date. The original entry must remain readable.
- Mixing up Study IDs — Use a sequential, never-reused ID system. Once a patient exits the study, their ID is retired.
- Not updating withdrawal reasons — Incomplete withdrawal records affect your CONSORT flow diagram and may be flagged by examiners.
CONSORT Diagram and Your Patient Log
At the time of writing your thesis, your patient log is the source document for your CONSORT (or STROBE, for observational studies) flow diagram. The numbers in your flow diagram — screened, enrolled, completed, withdrawn — must exactly match your patient log. Discrepancies here raise immediate questions about study conduct.
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See ThesisLog Features →Key Takeaways
- Start your patient log before you enroll the first patient.
- Separate your enrollment log from your analysis dataset.
- Update the log on the same day as each patient event.
- Keep a backup of your log at least weekly.
- Reconcile your log with your data sheet monthly to catch discrepancies early.
What Your Patient Log Should Contain
A well-maintained patient log should have these minimum fields:
- Sequential entry number — not the patient ID, just the log row number
- Screening date — when you first evaluated the patient for eligibility
- Patient ID — assigned only to those enrolled; leave blank for screen failures
- Eligibility status — Enrolled / Screen failure
- Exclusion reason — for every screen failure, document which criterion was not met
- Enrolment date — when the patient formally joined the study
- Withdrawal date and reason — if applicable during follow-up
Keep this log updated in real time. A log reconstructed from memory at the end of data collection will not survive scrutiny at your viva.
Frequently Asked Questions
What is a patient log in clinical research? +
A patient log (also called a subject log or enrolment log) is a chronological record of all patients screened for your study — including those who were excluded and why. It documents enrolment dates, patient IDs, eligibility status, and any protocol deviations. It is required for good clinical practice (GCP) compliance.
How is a patient log different from a data sheet? +
The patient log tracks who entered and exited your study and when. The data sheet tracks what you measured about each enrolled patient. Both are required: the log for audit trails and the data sheet for statistical analysis.
Do I need a patient log for a retrospective study? +
Yes. Even for retrospective studies, you need to document which records you screened, which met inclusion criteria, and which were excluded (with reasons). This forms part of your CONSORT or STROBE flow diagram, which journals and examiners expect.