Impact of Clinical Outcome Measures on Placebo Response Rates in Clinical Trials for Chronic Constipation: A Systematic Review and Meta-analysis

Efficacy and acceptability of different probiotic products plus laxatives for pediatric functional constipation: a network meta-analysis of randomized controlled trials

The prevalence of pediatric constipation ranges from 0.7 to 29.6% across different countries. Functional constipation accounts for 95% of pediatric constipation, and the efficacy of pharmacotherapy is limited, with a success rate of 60%. Several randomized controlled trials (RCTs) have shown the benefits of probiotic supplements in treating this condition. However, the reported strains of probiotics varied among the RCTs. We aimed to compare the efficacy and acceptability of different probiotic supplements for pediatric functional constipation. The current frequentist model-based network meta-analysis (NMA) included RCTs of probiotic supplements for functional constipation in children. The primary outcome was changes in bowel movement or stool frequency; acceptability outcome was all-cause discontinuation. Nine RCTs were included (N = 710; mean age = 5.5 years; 49.4% girls). Most probiotic products, used either alone or combined with laxatives, were associated with significantly better improvement in bowel movement or stool frequency than placebo/control. Protexin plus laxatives (standardized mean difference (SMD) = 1.87, 95% confidence interval (95% CI) = 0.85 to 2.90) were associated with the greatest improvement in bowel movement or stool frequency among all the investigated probiotic products. For the single probiotic interventions, only Lactobacillus casei rhamnosus Lcr35 was associated with significant efficacy compared to placebo/control treatments (SMD = 1.37, 95% CI: 0.32 to 2.43). All the investigated probiotic products had fecal incontinence and patient drop-out rates similar to those of placebo/control treatments.  Conclusion: The results of our NMA support the application of an advanced combination of probiotics and laxatives for pediatric functional constipation if there is no concurrent contraindication.  Registration: PROSPERO (CRD42022298724). What is Known: • Despite of the high prevalence of pediatric constipation, which ranges from 0.7% to 29.6%, the efficacy of pharmacotherapy is limited, with a success rate of 60%. Several randomized controlled trials (RCTs) have shown the benefits of probiotic supplements in treating this condition. However, the reported strains of probiotics varied among the RCTs. The widely heterogeneous strains of probiotics let the traditional meta-analysis, which pooled all different strains into one group, be nonsense and insignificant. What is New: • By conducting a comprehensive network meta-analysis, we aimed to compare the efficacy and acceptability of different strains of probiotic supplements for pediatric functional constipation. Network meta-analysis of nine randomized controlled trials revealed that the most probiotic products, used either alone or combined with laxatives, were associated with significantly better improvement in bowel movement or stool frequency than placebo/control. Protexin plus laxatives was associated with the greatest improvement in bowel movement or stool frequency among all the investigated probiotic products. For the single probiotic interventions, only Lactobacillus casei rhamnosus Lcr35 was associated with significant efficacy compared to placebo/control treatments. All the investigated probiotic products had fecal incontinence and patient drop-out rates similar to those of placebo/control treatments.

Randomized controlled trial of linaclotide in children aged 6-17 years with functional constipation

OBJECTIVES

Linaclotide, a guanylate cyclase-C agonist, was recently approved in the United States for treatment of children 6-17 years old with functional constipation (FC). This study evaluated the safety and efficacy of several linaclotide doses in children 6-17 years old with FC.

METHODS

In this multicenter, randomized, double-blind, placebo-controlled phase 2 study, 173 children with FC (based on Rome III criteria) were randomized to once-daily linaclotide (A: 9 or 18 μg, B: 18 or 36 μg, or C: 36 or 72 μg) or placebo in a 1:1:1:1 ratio for 6- to 11-year-olds (dosage determined by weight: 18 to <35 or ≥35 kg) and linaclotide (18, 36, 72, or 145 μg) or placebo in a 1:1:1:1:1 ratio for 12- to 17-year-olds. The primary efficacy endpoint was change from baseline in weekly spontaneous bowel movement (SBM) frequency throughout the 4-week treatment period. Adverse events (AE), clinical laboratory values, and electrocardiograms were monitored.

RESULTS

Efficacy and safety were assessed in 173 patients (52.0% aged 6-11 years; 48.0% aged 12-17 years); 162 (93.6%) completed the treatment period. A numerical improvement in mean SBM frequency was observed with increasing linaclotide doses (1.90 in 6- to 11-year-olds [36 or 72 μg] and 2.86 in 12- to 17-year-olds [72 μg]). The most reported treatment-emergent AE was diarrhea, with most cases being mild; none were severe.

CONCLUSIONS

Linaclotide was well tolerated in this pediatric population, with a trend toward efficacy in the higher doses, warranting further evaluation.

Placebo response to sham electroacupuncture in patients with chronic functional constipation: A secondary analysis

BACKGROUND

Chronic severe functional constipation is a common disease that requires novel and effective treatment strategies. Acupuncture might constitute a promising therapeutic approach for chronic constipation, but it reportedly engenders an enhanced placebo response. Herein, we aimed to determine the magnitude of the placebo responses to electroacupuncture for constipation and identify its influencing factors.

METHODS

In this secondary analysis of a multicenter randomized trial, patients were randomized to a sham electroacupuncture group, which was administered for 8 weeks in 24 sessions of superficial needling at nonacupoints. The placebo response rates were assessed using three responder criteria: ≥3 complete spontaneous bowel movements per week (CSBMs/week), overall CSBM, and sustained CSBM. Logistic regression with backward selection method was employed to identify the potential factors that affected the placebo response.

KEY RESULTS

Overall, 539 patients were included in the study. The placebo response rate was 10.58%, 9.46%, and 9.09% according to the three aforementioned criteria, respectively. Those who exhibited more CSBMs/week at baseline were more likely to respond to sham electroacupuncture. Among patients with more than one CSBM per week at baseline, the response rates for achieving the criteria of ≥3 CSBMs per week, overall CSBM, and sustained CSBM were 25.40%, 30.16%, and 22.22%.

CONCLUSIONS AND INFERENCE

Electroacupuncture did not demonstrate a large placebo response in functional constipation treatment. The number of CSBMs at baseline may be a moderator of the placebo response to sham electroacupuncture. Thus, superficial needling sham acupuncture may be considered an ideal sham control for clinical trials of chronic constipation.

Contextual effects: how to, and how not to, quantify them

The importance of contextual effects and their roles in clinical care controversial. A Cochrane review published in 2010 concluded that placebo interventions lack important clinical effects overall, but that placebo interventions can influence patient-reported outcomes such as pain and nausea. However, systematic reviews published after 2010 estimated greater contextual effects than the Cochrane review, which stems from the inappropriate methods employed to quantify contextual effects. The effects of medical interventions (i.e., the total treatment effect) can be divided into three components: specific, contextual, and non-specific. We propose that the most effective method for quantifying the magnitude of contextual effects is to calculate the difference in outcome measures between a group treated with placebo and a non-treated control group. Here, we show that other methods, such as solely using the placebo control arm or calculation of a 'proportional contextual effect,' are limited and should not be applied. The aim of this study is to provide clear guidance on best practices for estimating contextual effects in clinical research.

Nocebo effects and influencing factors in the randomized clinical trials of chronic constipation: A systematic review and meta-analysis

BACKGROUND

Nocebo effects are unavoidable in randomized clinical trials. We aimed to assess the magnitude of nocebo effects and explore the influencing factors in chronic constipation.

METHODS

We searched the PubMed, Embase, and Cochrane Library databases up to July 2022. Randomized, placebo-controlled trials investigating interventions in chronic constipation were included. We conducted a random effects meta-analysis of the proportion of adverse events (AEs) in placebo-treated participants and evaluated the effect of trial characteristics on nocebo effects.

KEY RESULTS

We identified 20,204 studies from the databases, of which 61 were included in the final analysis. The pooled placebo AE rate was 30.41%, and AE-related withdrawal rate was 1.53%. The most commonly reported AEs were headache (5.67%), diarrhea (4.45%), abdominal pain (3.98%), nasopharyngitis (3.39%), nausea (3.36%), and flatulence (2.95%). The placebo AE rate was lower in trials conducted in Asia compared to those in Europe, North America, and international trials. It was also lower in trials diagnosed by Rome III compared to clinician's opinion and Rome II. Additionally, the placebo AE rate was lower in single-center trials compared to multicenter trials, lower in 5-8 weeks therapy compared to 9-12 weeks therapy, lower in participants with FC compared to those with IBS-C and CC, lower in trials with 2 arms compared to 3 arms, and higher in trials with prokinetic drugs compared to secretagogues and laxatives.

CONCLUSIONS & INFERENCES

The placebo AE rate was 30.41% in patients with chronic constipation. Based on our findings, we recommend that researchers take the nocebo effects into consideration when designing and conducting clinical trials and adopt specific measures to mitigate the negative influence of nocebo effects.

Probiotics and synbiotics in chronic constipation in adults: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND & AIMS

Probiotics and synbiotics have been increasingly investigated for the management of chronic constipation. We aimed to investigate the effect of probiotics and synbiotics on stool output, gut transit time, symptoms and quality of life in adults with chronic constipation via a systematic review and meta-analysis of randomized controlled trials (RCTs).

METHODS

Studies were identified using electronic databases, backward citation and hand-searching abstracts. The search date was 10 July 2022. RCTs reporting administration of probiotics or synbiotics in adults with chronic constipation were included. Risk of bias (RoB) was assessed with the Cochrane RoB 2.0 tool. Meta-analysis was conducted separately for probiotics and synbiotics. Results were synthesized using risk ratios (RRs), mean differences or standardized mean differences (SMDs) and 95% confidence intervals (CIs) using a random-effects model.

RESULTS

Thirty RCTs investigating probiotics and four RCTs investigating synbiotics were included. Overall, 369/647 (57%) responded to probiotic treatment and 252/567 (44%) to control (RR 1.28, 95% CI 1.07, 1.52, p = 0.007). Probiotics increased stool frequency (SMD 0.71, 95% CI 0.37, 1.04, p < 0.00001), with Bifidobacterium lactis having a significant effect, but not mixtures of probiotics, Bacillus coagulans Unique IS2 or Lactobacillus casei Shirota. Probiotics did not impact stool consistency (SMD 0.26, 95% CI -0.03, 0.54, p = 0.08). Probiotics improved integrative symptom scores compared to control (SMD -0.46, 95% CI -0.89, -0.04). Synbiotics did not impact stool output or integrative symptom scores compared to control.

CONCLUSIONS

Certain probiotics may improve response to treatment, stool frequency and integrative constipation symptoms, providing cautious optimism for their use as a dietary management option. There is currently insufficient evidence to recommend synbiotics in the management of chronic constipation. Caution is needed when interpreting these results due to high heterogeneity and risk of bias amongst the studies.