Intervention credibility is of fundamental importance to researchers designing experimental evaluations: if the care provided in the intervention under investigation is not credible to practitioners who provide care, or the patients receiving it, then the research may underestimate its potential benefits or harm. Equally, if the comparator arm(s) is not thought to constitute credible care then researchers may be accused of attempting to exaggerate the effects of the intervention by choosing a therapeutically weak comparison.
Acupuncture is an example of a traditional medicine where researchers argue that the concept of model validity, in the context of an experimental evaluation, is of equal importance as internal or external validity . To have good model validity, an intervention should have good credibility with practitioners and patients; and also strong model congruity: the diagnosis, treatment, and outcomes should be a good “fit”, thus credibility is a central tenet of the model validity concept. Evaluating credible outcomes is one aspect of model validity that should not be overlooked and attempts have been made to design studies with relevant patient reported outcome measures (PROMS) [2,3]. Although, in some instances, even such measures do not always capture what is of greatest importance to the patients or study participants . For certain interventions (including acupuncture), this is of particular importance when the desired outcome for the patients may not be limited to medically defined measures of disease.
Depression is set to become the second leading cause of lost disability-adjusted life years by 2020 (see 5:250–1) . This illness affects many people's lives, either directly or indirectly, and the economic burden to society is considerable . It is of paramount importance that new and more effective treatments are identified that can better meet the needs of patients [7–10], for whom the illness is usually a chronic, recurring, and debilitating problem . There have already been a substantial number of trials of acupuncture for depression, most conducted in China, that have mainly focused on the short-term benefits of specific treatment protocols and techniques. This type of research has resulted in an evidence base that has weak model validity [1,12], and poor credibility among acupuncture practitioners (in Western contexts) because it does not reflect clinical practice . Additionally, it is debatable whether protocol acupuncture evaluations would constitute “best practice” or achieve optimal results as such treatment does not take into account the patient's changing needs and allow for modifications to be made—as would normally happen in routine clinical practice (in Western contexts). Furthermore, one of the strengths of Chinese medicine acupuncture is that, in theory at least, because of a conceptualization of therapeutic effects resulting from a bodily re-education or learning process , the treatment can potentially help to prevent future illness recurrences, as well as alleviate current problems. It is thus disappointing that the research to date has focused only upon symptom alleviation rather than this in addition to the potential for prevention . Although preventative treatment trials are more costly, an intervention that offers protective benefits would have considerable social and economic benefits, as estimates suggest only 20% of individuals suffer only one illness episode with the mean number of lifetime episodes being four .
One main aim of our research was to design a trial where therapeutic integrity is not compromised by the trial's design and the therapy provided has good credibility with practitioners/care providers. The research program was organized around a PICO (patients; intervention; comparison; outcomes) structure . In relation to patients we sought to identify particular patient groups, within the context of UK primary care where most depression is treated, for whom acupuncture could provide additional benefits and would have high credibility as such individuals might be more amenable to using the intervention, and participating in a trial. For the acupuncture intervention the main challenge was to find a way to “standardize” acupuncture care, and to define and delineate the parameters of treatment appropriately, while maintaining credibility and without compromising therapeutic integrity. In regard to the comparator arm we sought to identify which interventions would be credible comparisons; could be of most interest to stakeholders; and would prove feasible, and practical. Finally, in relation to outcomes, we sought to understand the perspectives of those giving and receiving acupuncture care to identify its potential consequences (positive and negative), and to identify or develop appropriate measurement instruments, or methods, to capture these.