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Cohort study
Third-generation CT has 100% sensitivity and specificity for identifying subarachnoid haemorrhage when it is carried out within 6 h of headache onset
  1. Robert F McCormack
  1. Department of Emergency Medicine, Buffalo General Hospital, Buffalo, NY 14203, USA
  1. Correspondence to Robert F McCormack
    Department of Emergency Medicine, Buffalo General Hospital, 100 High Street, Buffalo, NY 14203, USA; rmccormack{at}

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A complaint of acute onset headache mandates that subarachnoid haemorrhage (SAH) be excluded as the cause. Because of the less than perfect sensitivity of unenhanced head CT, standard practice is to follow a negative CT with lumbar puncture (LP) to exclude subarachnoid haemorrhage. Improvements in CT technology have raised the question of whether modern third-generation CT scanners are sensitive enough to adequately exclude subarachnoid haemorrhage.


This was a prospective multicentre cohort study conducted at 11 university affiliated tertiary care teaching hospitals in Canada between November 2000 and December 2009. Consecutive patients aged 15 or older who presented with acute non-traumatic headache or with syncope associated with a headache were eligible for the study. CT scans were ordered at …

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  • Competing interests None.