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Longitudinal Mode and Arms

Longitudinal Mode and Arms

Article ID RC-NAV-REC-02 — Longitudinal Mode & Arms
Domain Record Navigation
Applies To Longitudinal projects
Prerequisite RC-NAV-REC-01 — Record Navigation Overview
Version 1.0
Last Updated 2026
Author See KB-SOURCE-ATTESTATION.md
Related Topics RC-NAV-REC-01 — Record Navigation Overview, RC-NAV-REC-03 — Repeated Instruments & Repeated EventsRC-NAV-REC-04 — Record Status Dashboard & Other Record Links, RC-NAV-UI-01 — Project Navigation UI, RC-LONG-01 — Longitudinal Project Setup, RC-DE-03 — Longitudinal Projects & DAGsRC-DE-10 — Longitudinal & Repeated Data Entry

1. Overview

This article explains REDCap's Longitudinal mode and the concept of Arms — two features that allow data collection across multiple timepoints and participant cohorts. It describes how these features affect record navigation.

2. Key Concepts & Definitions

Longitudinal Mode

A project setting that enables data collection at multiple timepoints. Instead of a single set of instruments, a longitudinal project defines Events — named timepoints (e.g., Baseline, Week 4, Month 6) — and assigns instruments to each event.

Event

A named timepoint within a longitudinal project. Each event can have any subset of the project's instruments assigned to it. When viewing a record, each event appears as a separate column on the Record Home Page.

Arm

A named collection of events within a longitudinal project. A project can have multiple arms, each with a different set of events and instrument assignments. A given record belongs to exactly one arm at a time. Arms are typically used to separate participant cohorts (e.g., intervention group vs. placebo group).

3. How Longitudinal Mode Affects Navigation

3.1 Record Home Page in a Longitudinal Project

  • Instead of a single row of instrument dots, you see a grid: rows are instruments, columns are events.

  • Each dot represents a specific instrument within a specific event.

  • Click any dot to open that instrument for that event.

3.2 Record Status Dashboard in a Longitudinal Project

  • The dashboard displays the same grid layout — rows are records, columns are events and instruments.

  • If the project has multiple arms, the dashboard adds a tab for each arm at the top of the page.

  • Click a tab to view records belonging to that arm.

3.3 Add/Edit Records in a Project with Arms

  • An additional dropdown appears at the top of the Add/Edit Records page asking you to select an arm.

  • You must choose an arm before looking up or adding a record.

  • Records can only be found within the arm they belong to.

4. Step-by-Step: Working with Events and Arms

4.1 Navigating to a Record in a Specific Event

  • Go to Add/Edit Records or the Record Status Dashboard.

  • If arms exist, select the appropriate arm first.

  • Select or search for the record.

  • On the Record Home Page, locate the column for the event you want.

  • Click the dot for the instrument within that event.

4.2 Identifying Which Arm a Record Belongs To

  • The Record Home Page header or the arm tab on the Record Status Dashboard indicates the active arm.

  • A record can only appear under one arm. If you cannot find a record in one arm, check another arm.

5. Common Questions

Q: What is the difference between an event and an arm?

A: An event is a single timepoint (e.g., 'Baseline visit'). An arm is a collection of events that defines the overall study timeline for a particular cohort. Multiple arms let you define different timelines for different groups of participants.

Q: Can a record move from one arm to another?

A: Not typically during normal data entry. Arm assignment is usually set when a record is created. Moving records between arms requires administrative intervention.

Q: Do all instruments appear in every event?

A: No. The project designer assigns specific instruments to specific events. An instrument only appears in the events it has been designated for.

Q: I cannot find a record in Add/Edit Records. What should I check?

A: First confirm you have selected the correct arm from the dropdown. Records only appear in the arm they belong to.

6. Common Mistakes & Gotchas

  • Looking for a record in the wrong arm: records are arm-specific. If the arm dropdown is set incorrectly, the record will not appear in the search results.

  • Expecting all instruments in every event: instruments are assigned to events individually. An instrument that is not assigned to a given event will not appear in that event's column.

  • Confusing events with arms: events are timepoints within a study timeline; arms are parallel timelines for different cohorts. These are related but distinct concepts.