RESUMO
BACKGROUND: Behaviour change counselling (BCC) is an adaptation of motivational interviewing (MI) designed to maximize the effectiveness of time-limited health behaviour change consultations. To improve intervention quality and understanding of treatment effects, it is recommended that evaluations of health behaviour change interventions incorporate existing fidelity frameworks (e.g. The National Institutes of Health [NIH] Behaviour Change Consortium) and ensure that treatment fidelity is assessed and reported. PURPOSE: This systematic review was designed to examine (a) adherence to NIH fidelity recommendations, (b) provider fidelity to BCC and (c) impact of these variables on the real-world effectiveness of BCC for adult health behaviours and outcomes. METHODS AND RESULTS: Searches of 10 electronic databases yielded 110 eligible publications describing 58 unique studies examining BCC delivered within real-world healthcare settings by existing providers. Mean study adherence to NIH fidelity recommendations was 63.31% (Range 26.83%-96.23%). Pooled effect size (Hedges g) for short-term and long-term outcomes was .19 (95% CI [.11, .27]) and .09 (95% CI [.04, .13]), respectively. In separate, random-effects meta-regressions, neither short-term nor long-term effect sizes were significantly modified by adherence to NIH fidelity recommendations. For the subgroup of short-term alcohol studies (n = 10), a significant inverse relationship was detected (Coefficient = -.0114, 95% CI [-.0187, -.0041], p = .0021). Inadequate and inconsistent reporting within the included studies precluded planned meta-regression between provider fidelity and BCC effect size. CONCLUSIONS: Further evidence is needed to clarify whether adherence to fidelity recommendations modifies intervention effects. Efforts to promote transparent consideration, evaluation and reporting of fidelity are urgently needed. Research and clinical implications are discussed.