'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'.