TY - JOUR T1 - Methodological issues in pragmatic trials of complex interventions in primary care JF - British Journal of General Practice JO - Br J Gen Pract SP - 10 LP - 11 DO - 10.3399/bjgp12X616238 VL - 62 IS - 594 AU - Nadine Foster AU - Paul Little Y1 - 2012/01/01 UR - http://bjgp.org/content/62/594/10.abstract N2 - A distinction in trial design is made between explanatory (or efficacy) and pragmatic (or effectiveness) trials.1 These terms, originally coined by Schwartz and Lellouch in 1967, are used to describe trials that either test causal research hypotheses to determine whether an intervention works in tightly controlled conditions to achieve optimal efficacy and/or to understand the key mechanism of action (explanatory); or that help choose between options for care under the usual conditions in which those options may be offered (pragmatic).The pragmatic–explanatory distinction really comprises a continuous spectrum1 with many elements, from the breadth of eligibility criteria, the flexibility in intervention delivery, expertise of those delivering treatment, degree of standardisation of intervention protocol, the efforts to ensure compliance, through to specific approaches to analysis. Pragmatic trials are increasingly adopted to test the effectiveness of complex interventions for patients in primary care, but may have explanatory elements.The Medical Research Council Framework for the development and evaluation of complex interventions provides helpful guidance, as complex interventions involve a number of separate but interacting components which are likely to be important to the success of the intervention, although the ‘active ingredients’ are often difficult to specify.2,3 In developing a novel, complex intervention comprising separate elements — for example, an education package with exercises for back pain — a rigorous … ER -