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You may mean operable haematoma is 1 in 10,000. A lot of studies have shown in GCS 15 with significant head injury to cause LOC/amnesia etc there is a CT positive finding 3-4%. Unfortunately the incidence of skull # is ~one 300 taken. A person with GCS of 15 with skull # has 1 in 45 risk of underlying haematoma. So poor screening test 12,000 normal skull x-rays to detect 1 operable haematoma. There is strong feeling I know mainly in America and Australasia that skull x-rays are a poor tool. But as recently as this month in Annals of Emergency Medicine they looked at the literature for management of mild traumatic brain injury and felt they could not recommend skull x-rays. Its like a Christmas present why look at the box when you want to see inside? Andy -----Original Message----- From: Accident and Emergency Academic List [mailto:[log in to unmask]] On Behalf Of Adrian Fogarty Sent: 09 October 2002 00:03 To: [log in to unmask] Subject: Re: D-dimers and DVT That's grossly oversimplified, or perhaps I should say grossly misinterpreted Andy. If a patient is fully conscious and they have no skull fracture, then their risk of intracranial haematoma is around 1 in 10,000! In the right clinical context therefore a skull x-ray has an extremely high negative predictive value, hence the beauty of this relatively simple test in stratifying patients to go home. I can't let you get away with that one!! Adrian Fogarty ----- Original Message ----- From: Andrew Webster <mailto:[log in to unmask]> To: [log in to unmask] Sent: Tuesday, October 08, 2002 8:13 PM Subject: Re: D-dimers and DVT I think if our patients are negative moderate risk-no clexane until scan, high risk clexane.unfortunately haven't got the protocol in front of me and can not quite remember. I would say many protocols are not of a very high evidence base. Many are drawn up from consensus agreements eg. Resuscitation.why three minutes for shocks?. We all know skull x-rays may increase positive predictive value for intra cranial haemaoma. But as a screening test to go home.only about 40% sensitive. But they are still in most guidelines eg. Sign etc. Whereas a big study such as the Canadian CT head rule probably hasn't entered many protocols yet. Andy Webster