Overall less than 20% of brain tumour patients are alive 5 years after diagnosis, in part because they present late with large inoperable tumours.1 There is an urgent need to develop new sensitive tests of brain tumours to help general practitioners in primary care.2 The most common malignant primary brain tumour called glioblastoma is characterised by abnormal blood vessels resulting in a leaky Blood–Brain Barrier (BBB).3 Glial Fibrillary Acid Protein (GFAP) is unique to the brain and not present in normal peripheral blood. This evidence concerns the gene GFAP and glioblastoma.