Dataset Information

Duration of the common cold and similar continuous outcomes should be analyzed on the relative scale: a case study of two zinc lozenge trials.

ABSTRACT:

Background

The relative scale has been used for decades in analysing binary data in epidemiology. In contrast, there has been a long tradition of carrying out meta-analyses of continuous outcomes on the absolute, original measurement, scale. The biological rationale for using the relative scale in the analysis of binary outcomes is that it adjusts for baseline variations; however, similar baseline variations can occur in continuous outcomes and relative effect scale may therefore be often useful also for continuous outcomes. The aim of this study was to determine whether the relative scale is more consistent with empirical data on treating the common cold than the absolute scale.

Methods

Individual patient data was available for 2 randomized trials on zinc lozenges for the treatment of the common cold. Mossad (Ann Intern Med 125:81-8, 1996) found 4.0 days and 43% reduction, and Petrus (Curr Ther Res 59:595-607, 1998) found 1.77 days and 25% reduction, in the duration of colds. In both trials, variance in the placebo group was significantly greater than in the zinc lozenge group. The effect estimates were applied to the common cold distributions of the placebo groups, and the resulting distributions were compared with the actual zinc lozenge group distributions.

Results

When the absolute effect estimates, 4.0 and 1.77 days, were applied to the placebo group common cold distributions, negative and zero (i.e., impossible) cold durations were predicted, and the high level variance remained. In contrast, when the relative effect estimates, 43 and 25%, were applied, impossible common cold durations were not predicted in the placebo groups, and the cold distributions became similar to those of the zinc lozenge groups.

Conclusions

For some continuous outcomes, such as the duration of illness and the duration of hospital stay, the relative scale leads to a more informative statistical analysis and more effective communication of the study findings. The transformation of continuous data to the relative scale is simple with a spreadsheet program, after which the relative scale data can be analysed using standard meta-analysis software. The option for the analysis of relative effects of continuous outcomes directly from the original data should be implemented in standard meta-analysis programs.

SUBMITTER: Hemila H

PROVIDER: S-EPMC5427521 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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Publications

Duration of the common cold and similar continuous outcomes should be analyzed on the relative scale: a case study of two zinc lozenge trials.

Hemilä Harri H

BMC medical research methodology 20170512 1

<h4>Background</h4>The relative scale has been used for decades in analysing binary data in epidemiology. In contrast, there has been a long tradition of carrying out meta-analyses of continuous outcomes on the absolute, original measurement, scale. The biological rationale for using the relative scale in the analysis of binary outcomes is that it adjusts for baseline variations; however, similar baseline variations can occur in continuous outcomes and relative effect scale may therefore be ofte ...[more]

PMID: 28494765

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Project description:BackgroundEunkyosan (EKS), also known as the Yinqiaosan formula, is widely applied for the common cold in East Asia. Many clinical trials have reported the efficacy and safety of the EKS formula for the treatment of the common cold.ObjectivesThis study aimed to assess the clinical evidence for and against the use of EKS formula as a treatment for the common cold.Data sourcesThe following databases were searched from inception to the present: MEDINLE, EMBASE, CENTRAL, AMED CINAHL for English articles; OASIS, the Korean Traditional Knowledge Portal, the Korean Studies Information Service System, KoreaMed, the Korean Medical Database and DBPIA); and 3 Chinese databases, including CNKI (i.e., the China Academic Journal, the China Doctoral Dissertations and Master's Theses Full-text Database, the China Proceedings of Conference Full-Text Database and the Century Journal Project), Wanfang and VIP. In addition, we searched a Japanese database and conduct non-electronic searches of conference proceedings.Study eligibility criteriaProspective randomised controlled trials (RCTs) evaluating the effectiveness of EKS for the common cold were included in this review.ParticipantsAll types of common colds were eligible for inclusion. Participants who had both the common cold and other conditions were excluded. There were no restrictions based on other factors, such as age, sex, or symptom severity.InterventionsStudies that evaluated any type of formulation (ie, decoction, tablet, pill, powder) of EKS were eligible for inclusion.Study appraisal and synthesis methodsDifferences between intervention and control groups were assessed. Mean differences with 95% confidence intervals (CIs) were used to measure the effects of treatment for continuous data.Methods and analysisFourteen databases were searched in March 2018. We included RCTs examining EKS decoctions for any type of common cold. All RCTs of decoctions or modified decoctions were included. The methodological qualities of the RCTs were assessed using the Cochrane Collaboration tool for assessing risk of bias; confidence in the cumulative evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) instrument.ResultsA total of 315 potentially relevant studies were identified, and 4 RCTs met our inclusion criteria. Four RCTs tested the effects of EKS on the common cold, and all RCTs showed that EKS was superior regarding the treatment effect.LimitationsAll RCTs were conducted in China, and the generalisation of these results to other countries might be limited. Most trials did not use internationally recognised reliability and validity outcome measurements. Moreover, the result of the response rate can be distorted by the practitioner. Future trials in compliance with international standards in the evaluation of treatment effects may resolve this issue.ConclusionOur systemic review and meta-analysis provides suggestive evidence of the superiority of EKS over other therapies for treating the common cold. The level of evidence is low because of the high risk of bias.Implications of key findingsThe results of this systematic review and meta-analysis provide suggestive evidence of the superiority of EKS alone or combined with conventional drugs.Registration numberCRD42018087694.

Project description:BackgroundThe relative scale adjusts for baseline variability and therefore may lead to findings that can be generalized more widely. It is routinely used for the analysis of binary outcomes but only rarely for continuous outcomes. Our objective was to compare relative vs absolute scale pooled outcomes using data from a recently published Cochrane systematic review that reported only absolute effects of inhaled β2-agonists on exercise-induced decline in forced-expiratory volumes in 1 s (FEV1).MethodsFrom the Cochrane review, we selected placebo-controlled cross-over studies that reported individual participant data (IPD). Reversal in FEV1 decline after exercise was modeled as a mean uniform percentage point (pp) change (absolute effect) or average percent change (relative effect) using either intercept-only or slope-only, respectively, linear mixed-effect models. We also calculated the pooled relative effect estimates using standard random-effects, inverse-variance-weighting meta-analysis using study-level mean effects.ResultsFourteen studies with 187 participants were identified for the IPD analysis. On the absolute scale, β2-agonists decreased the exercise-induced FEV1 decline by 28 pp., and on the relative scale, they decreased the FEV1 decline by 90%. The fit of the statistical model was significantly better with the relative 90% estimate compared with the absolute 28 pp. estimate. Furthermore, the median residuals (5.8 vs. 10.8 pp) were substantially smaller in the relative effect model than in the absolute effect model. Using standard study-level meta-analysis of the same 14 studies, β2-agonists reduced exercise-induced FEV1 decline on the relative scale by a similar amount: 83% or 90%, depending on the method of calculating the relative effect.ConclusionsCompared with the absolute scale, the relative scale captures more effectively the variation in the effects of β2-agonists on exercise-induced FEV1-declines. The absolute scale has been used in the analysis of FEV1 changes and may have led to sub-optimal statistical analysis in some cases. The choice between the absolute and relative scale should be determined based on biological reasoning and empirical testing to identify the scale that leads to lower heterogeneity.

Dataset Information

Duration of the common cold and similar continuous outcomes should be analyzed on the relative scale: a case study of two zinc lozenge trials.

Background

Methods

Results

Conclusions

Publications

Duration of the common cold and similar continuous outcomes should be analyzed on the relative scale: a case study of two zinc lozenge trials.

Similar Datasets

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