Are placebo-controlled trials of creams for athlete’s foot still justified?

Consensus for the Treatment of Tinea Pedis: A Systematic Review of Randomised Controlled Trials

Objective: To systematically review literature enabling the comparison of the efficacy of pharmaceutical treatments for tinea pedis in adults. Design: Systematic review of randomised controlled trials (RCTs) with mycological cure as the primary outcome. Secondary outcomes did include the clinical assessment of resolving infection or symptoms, duration of treatment, adverse events, adherence, and recurrence. Eligibility Criteria: Study participants suffering from only tinea pedis that were treated with a pharmaceutical treatment. The study must have been conducted using an RCT study design and recording age of the participant > 16 years of age. Results: A total of seven studies met the inclusion criteria, involving 1042 participants. The likelihood of resolution in study participants treated with terbinafine was RR 3.9 (95% CI: 2.0−7.8) times those with a placebo. Similarly, the allylamine butenafine was effective by RR 5.3 (95% CI: 1.4−19.6) compared to a placebo. Butenafine was similarly efficacious to terbinafine RR 1.3 (95% CI: 0.4−4.4). Terbinafine was marginally more efficacious than itraconazole, RR 1.3 (95% CI: 1.1−1.5). Summary/Conclusion: Topical terbinafine and butenafine treatments of tinea pedis were more efficacious than placebo. Tableted terbinafine and itraconazole administered orally were efficacious in the drug treatment of tinea pedis fungal infection. We are concerned about how few studies were available that reported the baseline characteristics for each treatment arm and that did not suffer greater than 20% loss to follow-up. We would like to see improved reporting of clinical trials in academic literature. Registration name: Treatment’s for athlete’s foot—systematic review with meta-analysis [CRD42020162078].

Publication bias in dermatology systematic reviews and meta-analyses

Systematic reviews and meta-analyses in dermatology provide high-level evidence for clinicians and policy makers that influence clinical decision making and treatment guidelines. One methodological problem with systematic reviews is the under representation of unpublished studies. This problem is due in part to publication bias. Omission of statistically non-significant data from meta-analyses may result in overestimation of treatment effect sizes which may lead to clinical consequences. Our goal was to assess whether systematic reviewers in dermatology evaluate and report publication bias. Further, we wanted to conduct our own evaluation of publication bias on meta-analyses that failed to do so. Our study considered systematic reviews and meta-analyses from ten dermatology journals from 2006 to 2016. A PubMed search was conducted, and all full-text articles that met our inclusion criteria were retrieved and coded by the primary author. 293 articles were included in our analysis. Additionally, we formally evaluated publication bias in meta-analyses that failed to do so using trim and fill and cumulative meta-analysis by precision methods. Publication bias was mentioned in 107 articles (36.5%) and was formally evaluated in 64 articles (21.8%). Visual inspection of a funnel plot was the most common method of evaluating publication bias. Publication bias was present in 45 articles (15.3%), not present in 57 articles (19.5%) and not determined in 191 articles (65.2%). Using the trim and fill method, 7 meta-analyses (33.33%) showed evidence of publication bias. Although the trim and fill method only found evidence of publication bias in 7 meta-analyses, the cumulative meta-analysis by precision method found evidence of publication bias in 15 meta-analyses (71.4%). Many of the reviews in our study did not mention or evaluate publication bias. Further, of the 42 articles that stated following PRISMA reporting guidelines, 19 (45.2%) evaluated for publication bias. In comparison to other studies, we found that systematic reviews in dermatology were less likely to evaluate for publication bias. Evaluating and reporting the likelihood of publication bias should be standard practice in systematic reviews when appropriate.

Placebo cure rates in the treatment of onychomycosis

Placebo cure rates vary among randomized clinical trials for onychomycosis, but the factors influencing these cure rates have not been systematically investigated. The PubMed database and reference sections of relevant publications were searched for randomized controlled trials of dermatophyte toenail onychomycosis that included a placebo control and that assessed cure rates. From 21 studies, the pooled mean ± SD placebo cure rates regarding mycological, clinical, and complete cure were 8.7% ± 3.7%, 3.4% ± 2.2%, and 1.2% ± 1.4%, respectively. There was no statistically significant difference between oral and topical treatments. None of the cure rates significantly correlated with any of the participant or study design characteristics analyzed. Placebo cure rates in randomized controlled trials of toenail onychomycosis are relatively low and are independent of the study characteristics.

Efficacy and safety of topical antifungals in the treatment of dermatomycosis: a systematic review

The analysis of comparative efficacy and safety of topical antifungals in the literature is restricted to the treatment of tinea pedis and onychomycosis. Therefore our objective was to evaluate and compare the efficacy and safety of topical antifungals used in the treatment of dermatomycosis, we performed a comprehensive search for randomized controlled trials (RCTs) in the following databases: Medline, Cochrane Central Register of Controlled Trials, EMBASE, Lilacs and International Pharmaceutical Abstracts, we identified studies that compared the use of topical antifungals with other antifungals or with placebo published up to July 2010 in English, Spanish or Portuguese. The quality of reporting was assessed according to the Jadad scale; only studies with a score of 3 or more were included. The outcomes evaluated were mycological cure at the end of treatment, sustained cure, occurrence of adverse events and tolerability, including withdrawals due to adverse events. A total of 104 RCTs satisfied the inclusion criteria, containing a total of 135 comparisons, with 55 out of 120 possible comparisons among the 16 drugs evaluated. Pooled data on efficacy showed that all the antifungals were better than placebo. There were no significant differences among antifungal classes. No differences were found in safety or tolerability in any direct comparison. Sensitivity analysis indicated the robustness of the findings. Our results indicate the clear superiority of topical antifungals over placebo but that there is no consistent difference among classes. Mixed treatment comparisons are necessary to rank antifungals, as direct comparisons among many of them are lacking.

The placebo mystique: Implications for clinical trial methodology

AIM

The World Medical Association Declaration of Helsinki states that the use of a placebo in a clinical trial can only be justified ethically when no proven active treatment is available as a comparison. Despite this, placebos remain a popular choice as controls in clinical trials. Recent literature reviews have suggested that reliance on placebos may, in part, be because of methodological misconceptions about the need for placebos to control for the 'placebo effect'. This study aimed to assess doctors' understanding of the requirements for placebo use in clinical trials.

METHODS

Two hundred doctors working in tertiary hospitals in Melbourne, Australia were surveyed in regards to their understanding of the role of the placebo and placebo effects in clinical trials. There was a 72% response rate. Doctors were specifically asked if a placebo was required in a randomised clinical trial, in preference to another form of control, to control for the 'placebo effect'.

RESULTS

The majority of respondents (62%) incorrectly believed that placebos are essential to control for the 'placebo effect' in a randomised clinical trial.

CONCLUSIONS

Misconceptions about the methodological requirement for placebos in randomised controlled trials may influence researcher decisions to use placebo controls in unethical situations.