What the Newcastle-Ottawa Scale is
The Newcastle-Ottawa Scale (Wells GA et al., Ottawa Hospital Research Institute) rates cohort and case-control studies with stars in three sections: selection (up to 4), comparability (up to 2) and outcome for cohorts or exposure for case-control studies (up to 3). A study scores at most 9 stars.
Stars have no colour, so the figure uses the thresholds the AHRQ standards apply to them. Good: 3 or 4 stars in selection, 1 or 2 in comparability and 2 or 3 in outcome. Fair: 2 in selection, with the same in the other two. Poor: 0 or 1 in selection, 0 in comparability, or 0 or 1 in outcome.
The three sections
On the figure they are D1 to D3:
- D1 Selection
- D2 Comparability
- D3 Outcome (cohort) or exposure (case-control)
Good · Fair · Poor. Grey: cells not filled in yet.
From stars to an overall judgement
Paste the stars as they are (“3”, “***” or “★★”) and the tool converts them section by section. Only selection can come out fair.
Each study’s overall is poor if any section is poor; otherwise selection decides between good and fair. That is the AHRQ rule for the whole study, stricter than adding up stars.
The items of the scale
Cohort studies
- Selection 1) Representativeness of the exposed cohort
- Selection 2) Selection of the non exposed cohort
- Selection 3) Ascertainment of exposure
- Selection 4) Demonstration that outcome of interest was not present at start of study
- Comparability 1) Comparability of cohorts on the basis of the design or analysis (up to 2 stars)
- Outcome 1) Assessment of outcome
- Outcome 2) Was follow-up long enough for outcomes to occur
- Outcome 3) Adequacy of follow up of cohorts
Case-control studies
- Selection 1) Is the case definition adequate?
- Selection 2) Representativeness of the cases
- Selection 3) Selection of Controls
- Selection 4) Definition of Controls
- Comparability 1) Comparability of cases and controls on the basis of the design or analysis (up to 2 stars)
- Exposure 1) Ascertainment of exposure
- Exposure 2) Same method of ascertainment for cases and controls
- Exposure 3) Non-Response rate
Quoted from Wells GA et al. (Ottawa Hospital Research Institute). Each item awards at most one star, except comparability, which awards up to two.
How to make the Newcastle-Ottawa figure
- The table above is already set to Newcastle-Ottawa. Replace the example studies with yours, or paste the table from Excel or Google Sheets (the robvis template works).
- Pick the judgement for each domain and, if the instrument has one, press “Fill in the overall judgement” and correct what needs correcting.
- Download the traffic light plot, the summary plot or both: PDF or SVG when the journal wants vector artwork; PNG or TIFF at the column width and 300 or 600 dpi when it wants an image.
Frequently asked questions
How many stars does the Newcastle-Ottawa Scale have?
Nine at most: 4 for selection, 2 for comparability and 3 for outcome (cohort) or exposure (case-control).
Is there an official cut-off for “good quality”?
No. The scale defines none. Many reviews use the AHRQ conversion this tool applies; others use a total star count (for example, 7 or more). Say which one in your methods.
Can I use it for cross-sectional studies?
The original scale covers cohort and case-control studies. Adaptations for cross-sectional studies exist but are not part of it. The JBI checklist for analytical cross-sectional studies is in the instrument list.
Can I use the figure in my paper?
Yes. Unless you are signed in to a revisia account with a verified email, what you download carries a small revisia mark under the figure, outside the drawing. With a verified email the figure comes out clean, in the preview and in every format. The account is free.