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STROBE: Reporting Observational Studies

Learn how to apply the STROBE checklist to ensure your cohort, case-control, or cross-sectional study is reported completely and transparently.

You'll learn

How to apply the STROBE checklist to observational study reporting so nothing critical is omitted.

Use this when

You are writing up a cohort, case-control, or cross-sectional study.

What STROBE Is and Why It Exists

STROBE — Strengthening the Reporting of Observational Studies in Epidemiology — is a 22-item checklist published in 2007 across six major journals including The Lancet, BMJ, Annals of Internal Medicine, and PLoS Medicine. It was developed because observational studies were routinely published with critical methodological details omitted, making them impossible to replicate or appraise.

💡 STROBE is about reporting, not quality

STROBE does not tell you whether your study design is good — it tells you what to report so readers can judge for themselves. A study can fully comply with STROBE and still be methodologically weak, or be excellent but incompletely reported. Reporting and study quality are different things.

Three Designs, One Framework

STROBE has separate checklists for cohort studies, case-control studies, and cross-sectional studies. Most items are shared; a few differ. The key differences relate to how participants were selected and how exposure and outcome were measured.

Design	Participants selected by	Core challenge to report
Cohort	Exposure status, then followed for outcome	Loss to follow-up, selection bias, confounders
Case-control	Outcome status, then exposure measured retrospectively	Case and control source, matching criteria, recall bias
Cross-sectional	Neither exposure nor outcome — both measured simultaneously	Response rate, temporality cannot be established

Key STROBE Items to Get Right

●Item 6 — Participants: describe inclusion/exclusion criteria, sources, and selection methods. Include a flow diagram
●Item 7 — Variables: define all outcomes, exposures, and confounders, and how they were measured
●Item 8 — Data sources: describe data collection methods and any reliability/validity assessments
●Item 9 — Bias: describe potential sources of bias and how they were addressed
●Item 12 — Statistical methods: specify all statistical methods including those for confounding, subgroups, and missing data
●Item 16 — Numbers: report numbers eligible, excluded, included, and analyzed at each stage
●Item 17 — Descriptive data: Table 1 with complete baseline characteristics

⚠️ The most commonly omitted items

Systematic reviews of observational study reporting consistently find that bias discussion (item 9), missing data handling (part of item 12), and flow diagrams showing participant selection (item 13) are the most frequently omitted elements.

Writing the Methods Section Using STROBE

Use the STROBE checklist as a writing prompt, not just as a checklist at the end. Before writing, identify which item each paragraph in your Methods addresses.

1.Study design and setting (items 4–5): one sentence stating design, setting, dates, and follow-up period
2.Participants (item 6): eligibility criteria, source of participants, selection rationale
3.Variables (items 7–8): outcome(s), exposure(s), confounders — how each was defined and measured
4.Bias (item 9): explicitly state known sources and what you did to address them
5.Sample size (item 10): state whether a power calculation was done and on what assumptions
6.Statistical methods (item 12): name every method used, state software and version, describe missing data approach