Importance of diagnostic differences
Diagnostic differences were judged potentially important (category 1 or 2) in 34 (17%) cases overall (4 (2%) category 1; (30 15%) category 2); 55 (27.5%) category 3, 21 (10.5%) category 4; 41 (20.5%) category 5 and 49 (24.5%) category 6 (complete concordance). Importance of differences by disease area are reported in Figure 2. No adverse events occurred; all potentially serious differential diagnoses provided were excluded by appropriate investigation and follow-up. The four cases in category 1 were: post-concussive headache with differential diagnosis of chronic subdural haemorrhage offered (imaging was subsequently normal); headaches with differential diagnoses of migraine, and posterior fossa structural pathology (imaging was normal); lower limb sensory symptoms with differential diagnoses of a functional disorder, intracranial structural pathology and lumbar radiculopathy (imaging and nerve conduction studies were normal); and sensory symptoms and bowel/bladder symptoms following a fall, with differential diagnoses of cervical myelopathy and subdural haemorrhage; imaging showed cervical spinal cord compression resulting in neurosurgical referral.