Cited by 2,917Statistical Methods in EpidemiologyMeta-analysis and systematic reviewsStatistical Methods in Clinical Trials

Calculating the sample size required for developing a clinical prediction model

Open access
Riley, Richard D, Ensor, Joie, Snell, Kym I E, Harrell, Frank E, Martin, Glen P, Reitsma, Johannes B, Moons, Karel G M, Collins, Gary +1 more·2020·BMJ

Abstract

Clinical prediction models aim to predict outcomes in individuals, to inform diagnosis or prognosis in healthcare. Hundreds of prediction models are published in the medical literature each year, yet many are developed using a dataset that is too small for the total number of participants or outcome events. This leads to inaccurate predictions and consequently incorrect healthcare decisions for some individuals. In this article, the authors provide guidance on how to calculate the sample size required to develop a clinical prediction model.

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Registry

Crossref · 10.1136/bmj.m441

Cites

78 of 78 references verified0 citation errors · 0 not checkable

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  • The sample size needed to reduce model overfitting was calculated assuming an expected shrinkage rate of 10%, 30 variables, and R2cs 0.3, yielding 740 cases.

    “In step three, the sample size needed to reduce model overfitting is calculated, assuming an expected shrinkage rate of 10%, with an expected number of variables P to be included in the final predictive model of 30: S is the expected shrinkage factor, and the noise ratio evaluation index R2cs is 0.3; the calculated sample size is 740 cases.”

    From Machine learning-driven prediction model for successful weaning of patients from mechanical ventilation in ICU (2026) · cites this paper as Riley [13]

    The paper’s Step 3 section (page not available in our copy) supports calculating sample size to limit overfitting using 10% expected shrinkage, the number of candidate predictor parameters, and anticipated Cox–Snell R². It does not report the claimed calculation of 740 cases for 30 parameters and R²cs of 0.3; its worked examples use different inputs. (LLM, conf=0.86)

    Experimental — accuracy not yet measured
  • Genomic and molecular data support integration of tumour biology and genetic risk into decision-making, particularly in precision medicine applications.

    “Genomic and molecular data support integration of tumour biology and genetic risk into decision-making, particularly in precision medicine applications [42].”

    From Artificial Intelligence in Clinical Decision-Making: A Comprehensive Review of Diagnostic, Prognostic, and Therapeutic Applications, Validation Gaps, Bias, and Deployment Challenges (2026) · cites this paper as [42]

    The Abstract passage says clinical prediction models can use family history and biomarkers to inform diagnosis and prognosis. It does not address genomic or molecular data, tumour biology, genetic risk, or precision-medicine decisions; searches for those terms found no supporting passage in our copy. (LLM, conf=0.74)

    Experimental — accuracy not yet measured
  • The sample size calculated using Riley and colleagues' guidance is the minimum for a standard statistical model.

    “The sample size calculated this way is the minimum for a standard statistical model.”

    From Developing clinical prediction models: a step-by-step guide (2024) · cites this paper as [50]

  • Sample size calculations indicated a minimum sample of 2082 patients, which is larger than the available sample, raising concerns about possible overfitting.

    “Sample size calculations50 indicated a minimum sample of 2082 patients, which is larger than the available sample, raising concerns about possible overfitting issues (step 6).”

    From Developing clinical prediction models: a step-by-step guide (2024) · cites this paper as [50]

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Cites

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2 of the 80 references couldn’t be matched to a known paper.

Research works printed but not linked: 3

  1. Riley RD, van der Windt D, Croft P, etal , eds. Prognosis Research in Healthcare: Concepts, Methods and Impact. Oxford University Press, 2019.
  2. McFadden D. Conditional logit analysis of qualitative choice behavior. In: Zarembka P, ed. Frontiers in Econometrics New York. Academic Press, 1974: 104-42.
  3. Schmoor C, Sauerbrei W, Schumacher M. Sample size considerations for the evaluation of prognostic factors in survival analysis. Stat Med 2000;19:441-52. 10

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Authors
Riley, R. D., Ensor, J., Snell, K. I. E., Harrell, F. E., Martin, G. P., Reitsma, J. B., Moons, K. G. M., Collins, G., & van Smeden, M.
Affiliations
  • Keele University (GB)
  • Vanderbilt University (US)
  • Manchester Academic Health Science Centre (GB)
  • University Medical Center Utrecht (NL)
Corresponding author
Riley, Richard D
Venue
BMJ
Publisher
BMJ
Published
2020-03-18
Volume
368
Pages
m441
ISSN
1756-1833 (ISSN-L)
OpenAlex
W3012413426
Cited by
2,917
References
80
Citations by year
2026: 863 · 2025: 606 · 2024: 531 · 2023: 402 · 2022: 275 · 2021: 174 · 2020: 58 · 2012: 2
FWCI
160.59
Type
journal article
Language
en
Open access
Locations
  • BMJ (publishedVersion)
  • PubMed (publishedVersion)
  • Research Explorer (The University of Manchester) (publishedVersion, other-oa)
  • Keele Research Repository (Keele University) (submittedVersion, cc-by)
  • Utrecht University Repository (Utrecht University) (submittedVersion, other-oa)
  • HighWire Press Open Archive (submittedVersion)
  • University of Birmingham Research Portal (University of Birmingham) (submittedVersion)
Funders
  • Georgia Clinical and Translational Science Alliance (UL1TR002243)
  • Cancer Research UK (27294)
  • National Institute for Health and Care Research (SPCR-142)
  • Department of Health and Social Care
  • Nederlandse Organisatie voor Wetenschappelijk Onderzoek (91208004, 918.10.615, project 9120.8004)
  • National Institutes of Health (UL1TR002243)
  • NIHR School for Primary Care Research
  • National Center for Advancing Translational Sciences (TR002243)
Topics
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
  • Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
Keywords
sample size determination, clinical prediction model, model development, prediction accuracy, prognostic model, diagnostic model, small sample size
MeSH terms
Clinical Decision-Making, Forecasting, Humans, Models, Theoretical, Sample Size

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