Simpson et al's splendid evaluation of direct access concluded that direct access computerised tomography (CT) is now the preferred choice for patients with chronic daily headache in primary care.1 They decided this after a rigorous identification of abnormal findings in the study, plus an economic analysis comparing CT scanning with other investigative options. We believe there is a third option – of no investigation and no referral.
The first reason for our view is given in the paper itself. Sixty scans (1.4%) from 4404 yielded a probable cause of the headache. A further 401 (9.1%) had incidental abnormalities. Of the 60 with abnormalities likely to be causative of the headache, four meningiomas, two metastases, two pituitary tumours, and two colloid cysts were resected: four other lesions led to surgery. We do not know if any of these patients had their symptoms improved, or even if the abnormalities actually were the cause of the symptoms. Their Table 31 shows a higher rate of imaging abnormalities in an asymptomatic population than in the headache population (albeit using magnetic resonance imaging, that is more sensitive) making it very likely that some of the abnormalities were not relevant.
What the authors omit from their deliberations is the clinical cost of CT scanning. One in 8100 women aged 40 will develop cancer from a single CT brain scan, with some forms of CT scanning posing a one in 80 risk of causing a cancer.2–3 These figures surely tip the balance. We know that many patients suffering chronic headache request CT scanning for reassurance.4 We also know a negative scan does reduce requests for medical care.5 However, the ‘cost’ may be too high. We GPs need to be honest in advising the patient that over 300 scans will have to be done for one patient to have a treatable abnormality – with no guarantee of therapeutic success – and that 27 (9% of 300) incidental abnormalities will be found in these 300 scans. Finally for every 15 treatable tumours that are found, one new cancer will be caused (8/4404 divided by 1/8100). Scan, anyone?
REFERENCES
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