Clinical features of primary brain tumours: a case-control study using electronic primary care records.

Background: Around 4500 new primary brain tumours are diagnosed in the UK each year. Symptoms of these tumours have not previously been studied in primary care.

Aim: To identify and quantify the clinical features of brain tumours in primary care.

Design Of Study: Case-control study.

Setting: The General Practice Research Database, UK.

Method: A total of 3505 patients with primary brain tumours diagnosed between May 1988 and March 2006, and 17 173 controls, matched for age (to 1 year), sex, and general practice, were studied. Full medical records for 6 months before diagnosis were searched for reports of clinical features previously associated with brain tumours. Odds ratios were calculated for variables independently associated with cancer, using conditional logistic regression, as were the positive predictive values for patients consulting in primary care.

Results: Seven features were associated with brain tumours before diagnosis. Positive predictive values against a background risk of 0.013% were: new-onset seizure, 1.2% (95% confidence interval [CI] = 1.0 to 1.4); weakness (as a symptom), 3.0% (95% CI = 1.7 to 4.9); headache, 0.09% (95% CI = 0.08 to 0.10); confusion, 0.20% (95% CI = 0.16 to 0.24); memory loss, 0.036% (95% CI = 0.026 to 0.052); visual disorder, 0.035% (95% CI = 0.025 to 0.051); and the physical sign of motor loss on examination, 0.026% (95% CI = 0.024 to 0.030); all P<0.001, except for visual disorder, P = 0.005. In a sub-analysis by age, the maximum risk of a brain tumour with headache or new-onset seizures was found in the age group 60-69 years (0.13% and 2.3% respectively).

Conclusion: The findings suggest that isolated headache presented to primary care has too small a risk of an underlying brain tumour to warrant investigation at presentation. However, new-onset seizures should be investigated.