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

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.

SUBMITTER: Haas M

PROVIDER: S-EPMC2893201 | biostudies-literature | 2010 May

REPOSITORIES: biostudies-literature

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

Haas Mitchell M Schneider Michael M Vavrek Darcy D

Chiropractic & osteopathy 20100524

<h4>Background</h4>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.<h4>Methods</h4>Eighty participants were randomized to receive spinal manipulation or a light massage control (n ...[more]

PMID: 20497573

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Project description:BACKGROUND CONTEXT:The optimal number of visits for the care of cervicogenic headache (CGH) with spinal manipulative therapy (SMT) is unknown. PURPOSE:The present study aimed to identify the dose-response relationship between visits for SMT and chronic CGH outcomes and to evaluate the efficacy of SMT by comparison with a light-massage control. STUDY DESIGN/SETTING:This is a two-site, open-label randomized controlled trial. PATIENT SAMPLE:Participants were 256 adults with chronic CGH. OUTCOME MEASURES:The primary outcome was days with CGH in the previous 4 weeks evaluated at the 12- and 24-week primary end points. Secondary outcomes included CGH days at remaining end points, pain intensity, disability, perceived improvement, medication use, and patient satisfaction. METHODS:Participants were randomized to four dose levels of chiropractic SMT: 0, 6, 12, or 18 sessions. They were treated three times per week for 6 weeks and received a focused light-massage control at sessions when SMT was not assigned. Linear dose effects and comparisons with the no-manipulation control group were evaluated at 6, 12, 24, 39, and 52 weeks. The present study was funded by the National Center for Complementary and Integrative Health (R01AT006330) and is registered at ClinicalTrials.gov (NCT01530321). The authors declare no conflicts of interest. RESULTS:A linear dose-response was observed for all follow-ups, a reduction of approximately 1 CGH day/4 weeks per additional 6 SMT visits (p<.05); a maximal effective dose could not be determined. Cervicogenic headache days/4 weeks were reduced from about 16 to 8 for the highest and most effective dose of 18 SMT visits. Mean differences in CGH days/4 weeks between 18 SMT visits and control were -3.3 (p=.004) and -2.9 (p=.017) at the primary end points, and were similar in magnitude at the remaining end points (p<.05). Differences between other SMT doses and control were smaller in magnitude (p>.05). Cervicogenic headache intensity showed no important improvement nor differed by dose. Other secondary outcomes were generally supportive of the primary outcome. CONCLUSIONS:There was a linear dose-response relationship between SMT visits and days with CGH. For the highest and most effective dose of 18 SMT visits, CGH days were reduced by half and about 3 more days per month than for the light-massage control.

Project description:Cervicogenic headache (CEH) is a secondary headache which affects 1.0-4.6 % of the population. Although the costs are unknown, the health consequences are substantial for the individual; especially considering that they often suffers chronicity. Pharmacological management has no or only minor effect on CEH. Thus, we aim to assess the efficacy of chiropractic spinal manipulative therapy (CSMT) for CEH in a single-blinded placebo-controlled randomized clinical trial (RCT). According to the power calculations, we aim to recruit 120 participants to the RCT. Participants will be randomized into one of three groups; CSMT, placebo (sham manipulation) and control (usual non-manual management). The RCT consists of three stages: 1 month run-in, 3 months intervention and follow-up analyses at the end of intervention and 3, 6 and 12 months. Primary end-point is headache frequency, while headache duration, headache intensity, headache index (frequency × duration × intensity) and medicine consumption are secondary end-points. Primary analysis will assess a change in headache frequency from baseline to the end of intervention and to follow-up, where the groups CSMT and placebo and CSMT and control will be compared. Due to two group-comparisons, the results with p values below 0.025 will be considered statistically significant. For all secondary end-points and analyses, the significance level of 0.05 will be used. The results will be presented with the corresponding p values and 95 % confidence intervals. To our knowledge, this is the first prospective manual therapy three-armed single-blinded placebo-controlled RCT to be conducted for CEH. Current RCTs suggest efficacy in headache frequency, duration and intensity. However a firm conclusion requires clinical single-blinded placebo-controlled RCTs with few methodological shortcomings. The present study design adheres to the recommendations for pharmacological RCTs as far as possible and follows the recommended clinical trial guidelines by the International Headache Society. Trial registration ClinicalTrials.gov identifier: NCT01687881, 2 December 2012.

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

Publications

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

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