Evidence map›Paper›PMID 19519911›Full record

ArticleBMC medical research methodology2009

Estimating the number needed to treat from continuous outcomes in randomised controlled trials: methodological challenges and worked example using data from the UK Back Pain Exercise and Manipulation (BEAM) trial.

Robert Froud, Sandra Eldridge, Ranjit Lall, Martin Underwood

Abstract readComparative Study
PubMed Full text at PMC Publisher
In one paragraph

Article in BMC medical research methodology, 2009. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 25 papers, 3 of them syntheses that pooled it.

0numbers the graph read from it
0cells of the map it votes in
25citing papers in PubMed, 3 pooled it
–field-weighted citation impact
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

25 citing papers in PubMed, 3 syntheses or guidelines pooled it.

  1. Pooled it
  2. Pooled it
  3. Spinal manipulative therapy for chronic low-back pain.The Cochrane database of systematic reviews · 2011
    Pooled it
  4. Trial
  5. Trial
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  7. Dose-response and efficacy of spinal manipulation for care of chronic low back pain: a randomized controlled trial.The spine journal : official journal of the North American Spine Society · 2014
    Trial
  8. Trial
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  10. Article
  11. Review
  12. Article
  13. Review
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  16. Article
  17. Article
  18. Review
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  20. Responder analyses in randomised controlled trials for chronic low back pain: an overview of currently used methods.European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society · 2014
    Review
4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

4 authors.

Robert FroudCentre for Health Sciences, Barts and the London School of Medicine and Dentistry, London, E1 2AT, UK. r.j.froud@qmul.ac.uk
Sandra Eldridge
Ranjit Lall
Martin Underwood

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

backgroundReporting numbers needed to treat (NNT) improves interpretability of trial results. It is unusual that continuous outcomes are converted to numbers of individual responders to treatment (i.e., those who reach a particular threshold of change); and deteriorations prevented are only rarely considered. We consider how numbers needed to treat can be derived from continuous outcomes; illustrated with a worked example showing the methods and challenges.

methodsWe used data from the UK BEAM trial (n = 1, 334) of physical treatments for back pain; originally reported as showing, at best, small to moderate benefits. Participants were randomised to receive 'best care' in general practice, the comparator treatment, or one of three manual and/or exercise treatments: 'best care' plus manipulation, exercise, or manipulation followed by exercise. We used established consensus thresholds for improvement in Roland-Morris disability questionnaire scores at three and twelve months to derive NNTs for improvements and for benefits (improvements gained+deteriorations prevented).

resultsAt three months, NNT estimates ranged from 5.1 (95% CI 3.4 to 10.7) to 9.0 (5.0 to 45.5) for exercise, 5.0 (3.4 to 9.8) to 5.4 (3.8 to 9.9) for manipulation, and 3.3 (2.5 to 4.9) to 4.8 (3.5 to 7.8) for manipulation followed by exercise. Corresponding between-group mean differences in the Roland-Morris disability questionnaire were 1.6 (0.8 to 2.3), 1.4 (0.6 to 2.1), and 1.9 (1.2 to 2.6) points.

conclusionIn contrast to small mean differences originally reported, NNTs were small and could be attractive to clinicians, patients, and purchasers. NNTs can aid the interpretation of results of trials using continuous outcomes. Where possible, these should be reported alongside mean differences. Challenges remain in calculating NNTs for some continuous outcomes.

trial registrationUK BEAM trial registration: ISRCTN32683578.

Indexed as

Exercise TherapyBack PainBenchmarkingFemaleHumansMaleManipulation, SpinalPopulation SurveillanceRandomized Controlled Trials as TopicSurveys and QuestionnairesUnited Kingdom

Identifiers

PMID19519911
PMCPMC2702335

What OpenQuestion holds

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LicenceCC BY
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Registered trials

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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.