A few patients had class "4" history grades but no positive radio-allergosorbent test results. This may indicate an allergen yet to be discovered-possibly an occupational one-a non-IgE-mediated mechanism or perhaps an exceptional interference in the radio-allergosorbent test by antibodies of another class. Whatever the reason, in such cases referral to an allergy specialist would be recommended. Indeed, referral should be considered when either the patient's symptoms are not fully explained by the report or advice on management is required. We conclude that microcomputers are now powerful enough to operate a complex self-learning data base that may be used (a) for taking and analysing a standard history, (b) predicting the likely causes of symptoms, and (c) linking the results of IgE tests to the patient's history so that a valuable interpretation of the patient's symptoms can be used by the general practitioner as a basis for referral to an allergy specialist. This work would have been impossible without either the assistance of Josephine Merrett in processing the IgE tests or the support of the Post Office and Civil Service Sanatorium Society. Requests for reprints should be addressed to T 0 Merrett, RAST Allergy Unit, Benenden Chest Hospital, Cranbrook, Kent TN17 4AX References 'Ishizaka K, Ishizaka T, Hornbrook MH. Physico-chemical properties in reaginic antibody. J Immunol 1966;97 :840-53. 2 Johansson SGO. Raised levels of new immunoglobulin class (IgND) in asthma. Lancet 1967;ii:951-3. 3 Eriksson NE. Diagnosis of reaginic allergy with house dust, animal dander and allergens in adult patients. III. Case histories and combinations of case histories, skin tests, and RAST compared with provocation tests. Abstract Senior neuroradiologists or radiologists of 42 hospitals with computed tomography available for NHS patients in England and Wales were contacted by postal questionnaire about the use of this facility in the management of patients with acute head injuries. Replies were obtained from 39 hospitals. Requests for computed tomography from general surgeons or physicians and staff of accident and emergency departments received positive responses for scanning with only half to three-quarters the frequency of responses to requests from neurosurgeons. Continuous computed tomography facilities were available generally to neurosurgeons. The combined effect of partial responses to requests and the availability of the computed tomography service meant that only 44% of hospitals gave a continuous service for general surgeons or physicians. The percentage of hospitals giving a continuous service to accident and emergency departments was 54%. It appeared that computed tomography scanning was being used most often as a diagnostic/
