Contribution is not substitution: a literature review of advanced clinical practitioners and doctor substitution

Doctor substitution by advanced clinical practitioners (ACPs) has expanded across healthcare systems despite limited evidence concerning diagnostic quality, patient safety and workforce performance. This narrative review examined international literature relating to ACPs and analogous advanced practice providers, prioritising direct comparator studies reporting clinically meaningful outcomes. Searches covered MEDLINE, Embase, Scopus, Google Scholar and relevant grey literature. Evidence was synthesised across five domains: clinical effectiveness; diagnostic performance and prescribing; patient safety and supervision; productivity and cost-effectiveness; and medical training. Findings included differences in clinical assessment, poorer referral quality, greater investigation and specialist use, higher antibiotic and opioid prescribing, and lower productivity in some settings. Malpractice analyses identified recurring diagnostic failures. UK evidence concerning diagnostic performance, patient safety, medical education and wider system functioning remained limited. The findings challenge assumptions that substitution is principally a staffing intervention. The review proposes epistemic decoupling to describe the separation of clinical activity from the knowledge and judgement required to interpret it safely, potentially concealing medical dependence and displaced costs. Workforce policy should therefore require evidence that substitution preserves diagnostic quality, patient safety and healthcare system performance.