Poor quality evidence to support the use of biofeedback for the treatment of functional constipation in adults
- Correspondence to: Professor Arnold Wald, Department of Gastroenterology and Hepatology, University of Wisconsin Medical Foundation Centennial Building, 1685 Highland Ave, Madison, WI 53705-2281, USA;
Implications for practice and research
Currently, there is insufficient evidence to make conclusions regarding the efficacy and safety of biofeedback for patients with chronic constipation.
Further, well-designed randomised controlled trials are needed to allow definitive conclusions to be drawn.
Most patients with chronic constipation respond to conservative and pharmacological treatments. However, a minority of patients are refractory to treatment, one of the reasons being abnormalities of defaecation characterised by inability to relax the striated muscles which facilitate defaecation and/or ineffective defaecatory propulsive forces. Biofeedback, which employs instrumental learning through visual or auditory feedback using anorectal manometry or electromyography, has been recommended to improve muscle coordination in selected patients and successfully treat refractory constipation associated with demonstrable abnormalities.
All randomised trials evaluating biofeedback for chronic idiopathic constipation published through December 2013 were considered. Seventeen eligible studies with a total of 931 participants were evaluated, with a primary outcome of clinical improvement as defined by the studies. Secondary outcomes included quality of life and adverse events. Quality of methodology was assessed using the Cochrane risk of bias tool and overall quality of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria. A meta-analysis was not possible due to heterogeneity of study populations and the large range of different outcome measures.
Of the 17 trials, 16 were considered at ‘high risk of bias for blinding’. Of the three controlled studies which found biofeedback to be greatly superior to oral diazepam, sham biofeedback and conservative treatment (range 70–80% vs 22–23%), the authors concluded that the evidence was of ‘low or very low quality’, largely due to potential bias in blinding. They concluded that there is currently “insufficient evidence to allow firm conclusions regarding efficacy and safety of biofeedback for treatment of chronic constipation.”
While the Cochrane process is deservedly held in the highest respect, this review is critically flawed and a disservice to healthcare providers who manage intractable constipation. Patients with intractable constipation are a select group of individuals who are often referred to specialists and tertiary care centres, and are not to be equated with the vast majority of patients who seek treatment for functional constipation. Thus, the reviewers’ recommendation that future biofeedback trials should be carried out in primary care settings and compared with conventional treatments fails to acknowledge that these patients are largely evaluated at secondary and tertiary care centres because of their dissatisfaction with established available therapies. Holding behavioural studies to the same standard of masking as drug studies is not acceptable because behavioural (and also surgical) intervention studies can never meet that standard. In addition, the call for studies assessing the effectiveness of components of biofeedback is puzzling, if one accepts the authors’ conclusion that the evidence for biofeedback in its totality is insufficient.
There is always a place for well-designed trials in this field, but it is unclear in this case why the issue of a larger sample size was raised. When three rigorous trials comprising 370 patients with pelvic floor dyssynergia show a clear-cut superiority of biofeedback over the comparator groups, it makes little sense to ask for larger trials to make the same point. As a scientific wag might say, how large a sample is needed to show that parachutes reduce mortality in skydivers? With a minimal risk procedure such as biofeedback, what more is needed to demonstrate benefit in a highly selected group with refractory constipation, in view of the multiple positive studies which have been published in journals with rigorous peer review?1–5
Despite the obvious strengths of evidence-based research, reviews such as this can be misconstrued by practitioners and health system funders to the detriment of patients who will benefit from this minimal risk treatment. I would urge the readers and the writers of this review to reconsider the conclusions and to be more positive in their assessment of this very effective technique.