Dataset Information

Sample size requirements for separating out the effects of combination treatments: randomised controlled trials of combination therapy vs. standard treatment compared to factorial designs for patients with tuberculous meningitis.

ABSTRACT:

Background

In certain diseases clinical experts may judge that the intervention with the best prospects is the addition of two treatments to the standard of care. This can either be tested with a simple randomized trial of combination versus standard treatment or with a 2 x 2 factorial design.

Methods

We compared the two approaches using the design of a new trial in tuberculous meningitis as an example. In that trial the combination of 2 drugs added to standard treatment is assumed to reduce the hazard of death by 30% and the sample size of the combination trial to achieve 80% power is 750 patients. We calculated the power of corresponding factorial designs with one- to sixteen-fold the sample size of the combination trial depending on the contribution of each individual drug to the combination treatment effect and the strength of an interaction between the two.

Results

In the absence of an interaction, an eight-fold increase in sample size for the factorial design as compared to the combination trial is required to get 80% power to jointly detect effects of both drugs if the contribution of the less potent treatment to the total effect is at least 35%. An eight-fold sample size increase also provides a power of 76% to detect a qualitative interaction at the one-sided 10% significance level if the individual effects of both drugs are equal. Factorial designs with a lower sample size have a high chance to be underpowered, to show significance of only one drug even if both are equally effective, and to miss important interactions.

Conclusions

Pragmatic combination trials of multiple interventions versus standard therapy are valuable in diseases with a limited patient pool if all interventions test the same treatment concept, it is considered likely that either both or none of the individual interventions are effective, and only moderate drug interactions are suspected. An adequately powered 2 x 2 factorial design to detect effects of individual drugs would require at least 8-fold the sample size of the combination trial.

Trial registration

Current Controlled Trials ISRCTN61649292.

SUBMITTER: Wolbers M

PROVIDER: S-EPMC3040154 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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Publications

Sample size requirements for separating out the effects of combination treatments: randomised controlled trials of combination therapy vs. standard treatment compared to factorial designs for patients with tuberculous meningitis.

Wolbers Marcel M Heemskerk Dorothee D Chau Tran Thi Hong TT Yen Nguyen Thi Bich NT Caws Maxine M Farrar Jeremy J Day Jeremy J

Trials 20110202

<h4>Background</h4>In certain diseases clinical experts may judge that the intervention with the best prospects is the addition of two treatments to the standard of care. This can either be tested with a simple randomized trial of combination versus standard treatment or with a 2 x 2 factorial design.<h4>Methods</h4>We compared the two approaches using the design of a new trial in tuberculous meningitis as an example. In that trial the combination of 2 drugs added to standard treatment is assume ...[more]

PMID: 21288326

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Project description:BackgroundTuberculous meningitis is a serious form of tuberculosis (TB) that affects the meninges that cover a person's brain and spinal cord. It is associated with high death rates and with disability in people who survive. Corticosteroids have been used as an adjunct to antituberculous drugs to treat people with tuberculous meningitis, but their role has been controversial.ObjectivesTo evaluate the effects of corticosteroids as an adjunct to antituberculous treatment on death and severe disability in people with tuberculous meningitis.Search methodsWe searched the Cochrane Infectious Diseases Group Specialized Register up to the 18 March 2016; CENTRAL; MEDLINE; EMBASE; LILACS; and Current Controlled Trials. We also contacted researchers and organizations working in the field, and checked reference lists.Selection criteriaRandomized controlled trials that compared corticosteroid plus antituberculous treatment with antituberculous treatment alone in people with clinically diagnosed tuberculous meningitis and included death or disability as outcome measures.Data collection and analysisWe independently assessed search results and methodological quality, and extracted data from the included trials. We analysed the data using risk ratios (RR) with 95% confidence intervals (CIs) and used a fixed-effect model. We performed an intention-to-treat analysis, where we included all participants randomized to treatment in the denominator. This analysis assumes that all participants who were lost to follow-up have good outcomes. We carried out a sensitivity analysis to explore the impact of the missing data.Main resultsNine trials that included 1337 participants (with 469 deaths) met the inclusion criteria.At follow-up from three to 18 months, steroids reduce deaths by almost one quarter (RR 0.75, 95% CI 0.65 to 0.87; nine trials, 1337 participants, high quality evidence). Disabling neurological deficit is not common in survivors, and steroids may have little or no effect on this outcome (RR 0.92, 95% CI 0.71 to 1.20; eight trials, 1314 participants, low quality evidence). There was no difference between groups in the incidence of adverse events, which included gastrointestinal bleeding, invasive bacterial infections, hyperglycaemia, and liver dysfunction.One trial followed up participants for five years. The effect on death was no longer apparent at this time-point (RR 0.93, 95% CI 0.78 to 1.12; one trial, 545 participants, moderate quality evidence); and there was no difference in disabling neurological deficit detected (RR 0.91, 95% CI 0.49 to 1.69; one trial, 545 participants, low quality evidence).One trial included human immunodeficiency virus (HIV)-positive people. The stratified analysis by HIV status in this trial showed no heterogeneity, with point estimates for death (RR 0.90, 95% CI 0.67 to 1.20; one trial, 98 participants) and disability (RR 1.23, 95% CI 0.08 to 19.07; one trial, 98 participants) similar to HIV-negative participants in the same trial.Authors' conclusionsCorticosteroids reduce mortality from tuberculous meningitis, at least in the short term.Corticosteroids may have no effect on the number of people who survive tuberculous meningitis with disabling neurological deficit, but this outcome is less common than death, and the CI for the relative effect includes possible harm. However, this small possible harm is unlikely to be quantitatively important when compared to the reduction in mortality.The number of HIV-positive people included in the review is small, so we are not sure if the benefits in terms of reduced mortality are preserved in this group of patients.

Project description:BackgroundThe differential diagnosis between tuberculous meningitis (TBM) and bacterial meningitis (BM) remains challenging in clinical practice. This study aimed to establish a diagnostic model that could accurately distinguish TBM from BM.MethodsPatients with TBM or BM were recruited between January 2017 and January 2021 at Tongji Hospital (Qiaokou cohort) and Sino-French New City Hospital (Caidian cohort). The detection for indicators involved in cerebrospinal fluid (CSF) and T-SPOT assay were performed simultaneously. Multivariate logistic regression was used to create a diagnostic model.ResultsA total of 174 patients (76 TBM and 98 BM) and another 105 cases (39 TBM and 66 BM) were enrolled from Qiaokou cohort and Caidian cohort, respectively. Significantly higher level of CSF lymphocyte proportion while significantly lower levels of CSF chlorine, nucleated cell count, and neutrophil proportion were observed in TBM group when comparing with those in BM group. However, receiver operating characteristic (ROC) curve analysis showed that the areas under the ROC curve (AUCs) produced by these indicators were all under 0.8. Meanwhile, tuberculosis-specific antigen/phytohemagglutinin (TBAg/PHA) ratio yielded an AUC of 0.889 (95% CI, 0.840-0.938) in distinguishing TBM from BM, with a sensitivity of 68.42% (95% CI, 57.30%-77.77%) and a specificity of 92.86% (95% CI, 85.98%-96.50%) when a cutoff value of 0.163 was used. Consequently, we successfully established a diagnostic model based on the combination of TBAg/PHA ratio, CSF chlorine, CSF nucleated cell count, and CSF lymphocyte proportion for discrimination between TBM and BM. The established model showed good performance in differentiating TBM from BM (AUC: 0.949; 95% CI, 0.921-0.978), with 81.58% (95% CI, 71.42%-88.70%) sensitivity and 91.84% (95% CI, 84.71%-95.81%) specificity. The performance of the diagnostic model obtained in Qiaokou cohort was further validated in Caidian cohort. The diagnostic model in Caidian cohort produced an AUC of 0.923 (95% CI, 0.867-0.980) with 79.49% (95% CI, 64.47%-89.22%) sensitivity and 90.91% (95% CI, 81.55%-95.77%) specificity.ConclusionsThe diagnostic model established based on the combination of four indicators had excellent utility in the discrimination between TBM and BM.

Dataset Information

Sample size requirements for separating out the effects of combination treatments: randomised controlled trials of combination therapy vs. standard treatment compared to factorial designs for patients with tuberculous meningitis.

Background

Methods

Results

Conclusions

Trial registration

Publications

Sample size requirements for separating out the effects of combination treatments: randomised controlled trials of combination therapy vs. standard treatment compared to factorial designs for patients with tuberculous meningitis.

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