Unintended consequences: quantifying the benefits, iatrogenic harms and downstream cascade costs of musculoskeletal MRI in UK primary care.

Objectives: The largest proportion of general practitioner (GP) magnetic resonance imaging (MRI) is musculoskeletal (MSK), with consistent annual growth. With limited supporting evidence and potential harms from early imaging overuse, we evaluated practice to improve pathways and patient safety.

Methods: Cohort evaluation of routinely collected diagnostic and general practice data across a UK metropolitan primary care population.

'Diagnostic downshift': clinical and system consequences of extrapolating secondary care testing tactics to primary care.

Numerous drivers push specialist diagnostic approaches down to primary care ('diagnostic downshift'), intuitively welcomed by clinicians and patients. However, primary care's different population and processes result in under-recognised, unintended consequences. Testing performs poorer in primary care, with indication creep due to earlier, more undifferentiated presentation and reduced accuracy due to spectrum bias and the 'false-positive paradox'.