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Illustrating risk difference and number needed to treat from a randomized controlled trial of spinal manipulation for cervicogenic headache

Haas, M and Schneider, M and Vavrek, D (2010) Illustrating risk difference and number needed to treat from a randomized controlled trial of spinal manipulation for cervicogenic headache. Chiropractic and Osteopathy, 18. ISSN 1746-1340

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Abstract

Background: The number needed to treat (NNT) for one participant to benefit is considered a useful, clinically meaningful way of reporting binary outcomes from randomized trials. Analysis of continuous data from our randomized controlled trial has previously demonstrated a significant and clinically important difference favoring spinal manipulation over a light massage control.Methods: Eighty participants were randomized to receive spinal manipulation or a light massage control (n = 40/group). Improvements in cervicogenic headache pain (primary outcome), disability, and number in prior four weeks were dichotomized into binary outcomes at two thresholds: 30% representing minimal clinically important change and 50% representing clinical success. Groups were compared at 12 and 24-week follow-up using binomial regression (generalized linear models) to compute the adjusted risk difference (RD) between groups and number needed to treat (NNT) after adjusting for baseline differences between groups. Results were compared to logistic regression results.Results: For headache pain, clinically important improvement (30% or 50%) was more likely for spinal manipulation: adjusted RD = 17% to 27% and NNT = 3.8 to 5.8 (p = .005 to .028). Some statistically significant results favoring manipulation were found for headache disability and number.Conclusion: Spinal manipulation demonstrated a benefit in terms of a clinically important improvement of cervicogenic headache pain. The use of adjusted NNT is recommended; however, adjusted RD may be easier to interpret than NNT. The study demonstrated how results may depend on the threshold for dichotomizing variables into binary outcomes.Trial Registration: ClinicalTrials.gov NLM identifier NCT00246350. © 2010 Haas et al; licensee BioMed Central Ltd.


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Details

Item Type: Article
Status: Published
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Haas, M
Schneider, Mmjs5@pitt.eduMJS5
Vavrek, D
Date: 24 May 2010
Date Type: Publication
Journal or Publication Title: Chiropractic and Osteopathy
Volume: 18
DOI or Unique Handle: 10.1186/1746-1340-18-9
Schools and Programs: School of Health and Rehabilitation Sciences > Rehabilitation Science
Refereed: Yes
ISSN: 1746-1340
Date Deposited: 10 Nov 2016 16:20
Last Modified: 07 May 2019 13:55
URI: http://d-scholarship.pitt.edu/id/eprint/30282

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