Number needed to treat in COPD: exacerbations versus pneumonias
Open accessAbstract
BACKGROUND: Several recent trials in chronic obstructive pulmonary disease (COPD) have assessed the effectiveness of the fluticasone-salmeterol combination inhaler in preventing COPD exacerbations, while finding an increased risk of pneumonia. The number needed to treat (NNT) is a simple measure to perform the comparative benefit-risk impact, but its calculation involving repeated outcome events such as COPD exacerbations has been incorrect. We describe the proper methods to calculate the NNT and, using data from published trials, apply them to evaluate the relative impact of fluticasone-salmeterol treatment on exacerbations and pneumonias in patients with COPD. METHODS: We review the fundamental definition of NNT and quantify it for situations with varying follow-up times. We review the 'event-based' NNT, proposed and used for repeated event outcomes, show its inaccuracy, describe its proper use and provide an approximate formula for its application. RESULTS: We show that a 1-year trial of the fluticasone-salmeterol combination versus salmeterol used the incorrect event-based approach to calculate the NNT as two patients that need to be treated for 1 year to prevent one COPD exacerbation, when the proper calculation results in a NNT of 14. In contrast, 20 patients need to be treated to induce one pneumonia case. For the TORCH trial, the NNT is 44 patients treated for 3 years with fluticasone-salmeterol versus salmeterol to prevent one exacerbation compared with 16 patients to induce one pneumonia case. CONCLUSIONS: The NNT is a useful measure of the effect of drugs, but its proper calculation is essential to prevent misleading clinical practice guidelines.
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A higher NNT (less effective) has been reported for bronchodilators to prevent an exacerbation, not a hospitalization.
“A higher NNT (less effective) has been reported for bronchodilators to prevent an exacerbation, not a hospitalization (33, 34).”
From Health Coaching and Chronic Obstructive Pulmonary Disease Rehospitalization: A Randomized Study (2016) · cites this paper as [33]
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- Authors
- Suissa, S.
- Affiliations
- Jewish General Hospital (CA)
- Corresponding author
- Suissa, Samy
- ORCID
- Suissa, Samy
- Venue
- Thorax
- Publisher
- BMJ
- Published
- 2012-11-02
- Volume
- 68
- Issue
- 6
- Pages
- 540-543
- ISSN
- 0040-6376 (ISSN-L)
- 1468-3296
- OpenAlex
- W2127142891
- Cited by
- 77
- References
- 21
- Citations by year
- 2025: 1 · 2024: 4 · 2021: 4 · 2020: 4 · 2019: 7 · 2018: 10 · 2017: 9 · 2016: 7 · 2015: 12 · 2014: 10 · 2013: 8 · 2012: 1
- FWCI
- 8.00
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Thorax (publishedVersion)
- PubMed (publishedVersion)
- HighWire Press Open Archive (submittedVersion)
- Topics
- Health Sciences › Medicine › Pulmonary and Respiratory Medicine › Chronic Obstructive Pulmonary Disease (COPD) Research
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
- Keywords
- number needed to treat, chronic obstructive pulmonary disease, COPD exacerbations, pneumonia, salmeterol/fluticasone, salmeterol, risk-benefit assessment, TORCH trial, inhaled corticosteroids
- MeSH terms
- Anti-Inflammatory Agents, Humans, Pneumonia, Global Health, Incidence, Pulmonary Disease, Chronic Obstructive
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
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