Clinical research in interventional pain management techniques: the clinician's point of view

Interventional pain management techniques are considered for patients whose pain proves refractory to conventional treatment. According to the evidence-based medicine (EBM) guidelines, the highest level of evidence for efficacy and safety of a treatment is generated in high-quality randomized controlled trials and systematic reviews. A randomized controlled trial is defined as an experiment that determines the influence of an intervention on the natural history of the disease, which means that the comparative group should receive placebo, which is a sham intervention in case of the interventional pain management techniques. The systematic review summarizes in a structured way the results of the available information. When randomized controlled trials are available, observational studies will often be discarded. As new information on a treatment becomes available the perceived value may change, thus determining the survival time of clinical evidence. This survival time is not different when based on randomized or nonrandomized studies. The inclusion criteria are an important component of the randomized controlled trial and are designed to test a treatment in a homogeneous patient population. As interventional pain management techniques are mainly used for the management of spinal pain, it needs to be stressed that there is no gold standard for the diagnosis. This lack of validated standard diagnostic procedures is at the origin of different patient selection criteria, which makes the interpretation of the different randomized controlled trials and the meta-analyses very difficult. Moreover, the extrapolation of randomized controlled trials with carefully selected patient populations to daily practice is a major problem. Randomized controlled trials in interventional pain management techniques often prove to be underpowered, which can be attributed to the difficulty in motivating patients and the referring physicians to participate in a trial where there is 50% chance of receiving a placebo/sham for intractable pain. Furthermore, the validity of sham intervention as a reflection of the natural course of the disease is questioned. It is stated that any new technique should prove to be at least equally effective as the best available treatment option, which offers the possibility of comparing two groups, both receiving active treatment. The reference treatment may be pharmacological or a rehabilitation program (cognitive behavioral) in which case blinding becomes a problem. It has been demonstrated that large observational studies with a cohort or case-control design do not systematically overestimate the magnitude of the associations between exposure and outcome as compared with the results of randomized controlled trials. There is an urgent need for guidelines on performing prospective cohort trials that should be designed to confirm or refute the anecdotal findings from retrospective studies.