Study type

Cohort study Case-control study

Selection (max 4 stars)

Representativeness of the exposed cohort is adequate (truly or somewhat representative) The non-exposed cohort is drawn from the same community as the exposed cohort Exposure is ascertained from a secure record (e.g. surgical/medical records) or structured interview The outcome of interest was not present at the start of the study

Comparability (max 2 stars)

Study controls for the most important confounding factor (specify in your write-up) Study controls for any additional confounding factor

Outcome (max 3 stars)

Outcome assessment is by independent blind assessment or record linkage Follow-up was long enough for outcomes to occur Adequacy of follow-up of cohorts (complete follow-up, or loss unlikely to introduce bias — typically ≥80%)

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About the Newcastle-Ottawa Scale

The NOS is a widely used tool for assessing the methodological quality of non-randomized studies (cohort and case-control designs) included in a systematic review or meta-analysis. It scores studies across three domains — Selection, Comparability, and Outcome (cohort) or Exposure (case-control) — for a maximum of 9 stars. This calculator applies the standard AHRQ conversion of star totals to Good/Fair/Poor ratings.

Always report your item-by-item NOS scoring in your methods or supplementary materials, not just the total — reviewers and readers expect to see how each study was judged, not just the final star count.

Need help applying quality assessment across your full study set?

Our team applies RoB 2, ROBINS-I, or the Newcastle-Ottawa Scale consistently across every included study, with a documented rationale for each rating.

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Newcastle-Ottawa Scale Calculator

About the Newcastle-Ottawa Scale

Need help applying quality assessment across your full study set?